[{"id":15671,"web_url":"https://patchwork.libcamera.org/comment/15671/","msgid":"","date":"2021-03-14T02:13:13","subject":"Re: [libcamera-devel] [PATCH 8/8] [RFC-Only] libcamera: request: A\n\trequest canary","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Kieran,\n\nThank you for the patch.\n\nOn Fri, Mar 12, 2021 at 06:11:31AM +0000, Kieran Bingham wrote:\n> Request objects are created and owned by the application, but are of\n> course utilised widely throughout the internals of libcamera.\n> \n> If the application free's the requests while they are still active\n> within libcamera a use after free will occur. While this can be trapped\n> by tools such as valgrind, given the importance of this object and the\n> relationship of external ownership, it may have some value to provide\n> Debug build (disabled at Release build) assertions on the condition of\n> these objects.\n> \n> Make sure the request fails an assertion immediately if used after free.\n> \n> Signed-off-by: Kieran Bingham \n> \n> ---\n> RFC only, as I was going to dispose of this patch. We added it while\n> debugging the IPU3 stability, and it may prove useful to catch errors if\n> requests are used after they are released.\n> \n> However this may be redundant as pipeline handlers should guarantee that\n> requests are fully completed when they stop(). Of course the IPU3 wasn't\n> meeting that requirement, and we do not have a specific assertion that\n> validates that requirement on all pipeline handlers. So perhaps this\n> canary might serve as a beneficial guard?\n\nI think we should move that check from the IPU3 pipeline handler to the\ncore, as commented on the corresponding patch, so this patch wouldn't\nreally be needed.\n\n> If not, at least posting it will mean it can be used in the future if it\n> comes up again, or the concept could be applied to other objects if\n> appropriate.\n> \n> include/libcamera/request.h | 2 ++\n> src/libcamera/request.cpp | 15 +++++++++++++++\n> 2 files changed, 17 insertions(+)\n> \n> diff --git a/include/libcamera/request.h b/include/libcamera/request.h\n> index 59d7f4bac0d2..fc56d63c8c67 100644\n> --- a/include/libcamera/request.h\n> +++ b/include/libcamera/request.h\n> @@ -78,6 +78,8 @@ private:\n> \tconst uint64_t cookie_;\n> \tStatus status_;\n> \tbool cancelled_;\n> +\n> +\tint canary_;\n\nIf we want to do this, couldn't we add a RequestFreed status to avoid\nadding a separate field ?\n\n> };\n> \n> } /* namespace libcamera */\n> diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp\n> index 12c2e7d425f9..83169a11e1e5 100644\n> --- a/src/libcamera/request.cpp\n> +++ b/src/libcamera/request.cpp\n> @@ -18,6 +18,8 @@\n> #include \"libcamera/internal/log.h\"\n> #include \"libcamera/internal/tracepoints.h\"\n> \n> +#define REQUEST_CANARY 0x1F2E3D4C\n> +\n> /**\n> * \\file request.h\n> * \\brief Describes a frame capture request to be processed by a camera\n> @@ -89,6 +91,8 @@ Request::Request(Camera *camera, uint64_t cookie)\n> \n> \tLIBCAMERA_TRACEPOINT(request_construct, this);\n> \n> +\tcanary_ = REQUEST_CANARY;\n> +\n> \tLOG(Request, Debug) << \"Created request - cookie: \" << cookie_;\n> }\n> \n> @@ -99,6 +103,8 @@ Request::~Request()\n> \tdelete metadata_;\n> \tdelete controls_;\n> \tdelete validator_;\n> +\n> +\tcanary_ = 0;\n> }\n> \n> /**\n> @@ -113,6 +119,8 @@ Request::~Request()\n> */\n> void Request::reuse(ReuseFlag flags)\n> {\n> +\tASSERT(canary_ == REQUEST_CANARY);\n> +\n> \tLIBCAMERA_TRACEPOINT(request_reuse, this);\n> \n> \tpending_.clear();\n> @@ -176,6 +184,8 @@ void Request::reuse(ReuseFlag flags)\n> */\n> int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)\n> {\n> +\tASSERT(canary_ == REQUEST_CANARY);\n> +\n> \tif (!stream) {\n> \t\tLOG(Request, Error) << \"Invalid stream reference\";\n> \t\treturn -EINVAL;\n> @@ -211,6 +221,8 @@ int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)\n> */\n> FrameBuffer *Request::findBuffer(const Stream *stream) const\n> {\n> +\tASSERT(canary_ == REQUEST_CANARY);\n> +\n> \tconst auto it = bufferMap_.find(stream);\n> \tif (it == bufferMap_.end())\n> \t\treturn nullptr;\n> @@ -262,6 +274,7 @@ FrameBuffer *Request::findBuffer(const Stream *stream) const\n> */\n> void Request::complete()\n> {\n> +\tASSERT(canary_ == REQUEST_CANARY);\n> \tASSERT(status_ == RequestPending);\n> \tASSERT(!hasPendingBuffers());\n> \n> @@ -289,6 +302,8 @@ void Request::complete()\n> */\n> bool Request::completeBuffer(FrameBuffer *buffer)\n> {\n> +\tASSERT(canary_ == REQUEST_CANARY);\n> +\n> \tLIBCAMERA_TRACEPOINT(request_complete_buffer, this, buffer);\n> \n> \tint ret = pending_.erase(buffer);","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id B50E5BD80C\n\tfor ;\n\tSun, 14 Mar 2021 02:13:51 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 20A9F60850;\n\tSun, 14 Mar 2021 03:13:51 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id CC8BA6084D\n\tfor ;\n\tSun, 14 Mar 2021 03:13:49 +0100 (CET)","from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi\n\t[62.78.145.57])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 0E91E55C;\n\tSun, 14 Mar 2021 03:13:48 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"d3BQ2koN\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1615688029;\n\tbh=WDK+RCccB+ugL+4OPIjaN1f060e9xbqrupo7Y0vjfvo=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=d3BQ2koNr5Mn2glZlBjSYeU7iBOvUh+C/7dBlvSBJ1J+eF0ia8ZPkH5oorhBEWGCG\n\tV3Vc5/nqSFqsUnFsNZOhpwwOrtRdcPwuXfnwXcAehaExCfM2ry9llxG6D6P5QUj6tp\n\teqb+t0Tdzxz7k3WNd4Rjzhqtnc7300UyGQFFNj5s=","Date":"Sun, 14 Mar 2021 04:13:13 +0200","From":"Laurent Pinchart ","To":"Kieran Bingham ","Message-ID":"","References":"<20210312061131.854849-1-kieran.bingham@ideasonboard.com>\n\t<20210312061131.854849-9-kieran.bingham@ideasonboard.com>","MIME-Version":"1.0","Content-Disposition":"inline","In-Reply-To":"<20210312061131.854849-9-kieran.bingham@ideasonboard.com>","Subject":"Re: [libcamera-devel] [PATCH 8/8] [RFC-Only] libcamera: request: A\n\trequest canary","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"libcamera devel ","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":15695,"web_url":"https://patchwork.libcamera.org/comment/15695/","msgid":"","date":"2021-03-15T11:24:45","subject":"Re: [libcamera-devel] [PATCH 8/8] [RFC-Only] libcamera: request: A\n\trequest canary","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"Hi Laurent,\n\nOn 14/03/2021 02:13, Laurent Pinchart wrote:\n> Hi Kieran,\n> \n> Thank you for the patch.\n> \n> On Fri, Mar 12, 2021 at 06:11:31AM +0000, Kieran Bingham wrote:\n>> Request objects are created and owned by the application, but are of\n>> course utilised widely throughout the internals of libcamera.\n>>\n>> If the application free's the requests while they are still active\n>> within libcamera a use after free will occur. While this can be trapped\n>> by tools such as valgrind, given the importance of this object and the\n>> relationship of external ownership, it may have some value to provide\n>> Debug build (disabled at Release build) assertions on the condition of\n>> these objects.\n>>\n>> Make sure the request fails an assertion immediately if used after free.\n>>\n>> Signed-off-by: Kieran Bingham \n>>\n>> ---\n>> RFC only, as I was going to dispose of this patch. We added it while\n>> debugging the IPU3 stability, and it may prove useful to catch errors if\n>> requests are used after they are released.\n>>\n>> However this may be redundant as pipeline handlers should guarantee that\n>> requests are fully completed when they stop(). Of course the IPU3 wasn't\n>> meeting that requirement, and we do not have a specific assertion that\n>> validates that requirement on all pipeline handlers. So perhaps this\n>> canary might serve as a beneficial guard?\n> \n> I think we should move that check from the IPU3 pipeline handler to the\n> core, as commented on the corresponding patch, so this patch wouldn't\n> really be needed.\n> \n>> If not, at least posting it will mean it can be used in the future if it\n>> comes up again, or the concept could be applied to other objects if\n>> appropriate.\n>>\n>> include/libcamera/request.h | 2 ++\n>> src/libcamera/request.cpp | 15 +++++++++++++++\n>> 2 files changed, 17 insertions(+)\n>>\n>> diff --git a/include/libcamera/request.h b/include/libcamera/request.h\n>> index 59d7f4bac0d2..fc56d63c8c67 100644\n>> --- a/include/libcamera/request.h\n>> +++ b/include/libcamera/request.h\n>> @@ -78,6 +78,8 @@ private:\n>> \tconst uint64_t cookie_;\n>> \tStatus status_;\n>> \tbool cancelled_;\n>> +\n>> +\tint canary_;\n> \n> If we want to do this, couldn't we add a RequestFreed status to avoid\n> adding a separate field ?\n\nIt's tempting to add/handle this to the state machine indeed, but we are\nlimited on the guarantees we can make there.\n\nAfter a free - we can't guarantee that Request->status() == RequestFreed :-)\n\nThe point of the canary is to assert that it has not been free'd and\nthat the values match exactly.\n\nMaybe a RequestFreed state will add some protection though - but as this\nis RFC only - we can leave it to think about if we end up digging in\nhere again.\n\n\n>> };\n>> \n>> } /* namespace libcamera */\n>> diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp\n>> index 12c2e7d425f9..83169a11e1e5 100644\n>> --- a/src/libcamera/request.cpp\n>> +++ b/src/libcamera/request.cpp\n>> @@ -18,6 +18,8 @@\n>> #include \"libcamera/internal/log.h\"\n>> #include \"libcamera/internal/tracepoints.h\"\n>> \n>> +#define REQUEST_CANARY 0x1F2E3D4C\n>> +\n>> /**\n>> * \\file request.h\n>> * \\brief Describes a frame capture request to be processed by a camera\n>> @@ -89,6 +91,8 @@ Request::Request(Camera *camera, uint64_t cookie)\n>> \n>> \tLIBCAMERA_TRACEPOINT(request_construct, this);\n>> \n>> +\tcanary_ = REQUEST_CANARY;\n>> +\n>> \tLOG(Request, Debug) << \"Created request - cookie: \" << cookie_;\n>> }\n>> \n>> @@ -99,6 +103,8 @@ Request::~Request()\n>> \tdelete metadata_;\n>> \tdelete controls_;\n>> \tdelete validator_;\n>> +\n>> +\tcanary_ = 0;\n>> }\n>> \n>> /**\n>> @@ -113,6 +119,8 @@ Request::~Request()\n>> */\n>> void Request::reuse(ReuseFlag flags)\n>> {\n>> +\tASSERT(canary_ == REQUEST_CANARY);\n>> +\n>> \tLIBCAMERA_TRACEPOINT(request_reuse, this);\n>> \n>> \tpending_.clear();\n>> @@ -176,6 +184,8 @@ void Request::reuse(ReuseFlag flags)\n>> */\n>> int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)\n>> {\n>> +\tASSERT(canary_ == REQUEST_CANARY);\n>> +\n>> \tif (!stream) {\n>> \t\tLOG(Request, Error) << \"Invalid stream reference\";\n>> \t\treturn -EINVAL;\n>> @@ -211,6 +221,8 @@ int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)\n>> */\n>> FrameBuffer *Request::findBuffer(const Stream *stream) const\n>> {\n>> +\tASSERT(canary_ == REQUEST_CANARY);\n>> +\n>> \tconst auto it = bufferMap_.find(stream);\n>> \tif (it == bufferMap_.end())\n>> \t\treturn nullptr;\n>> @@ -262,6 +274,7 @@ FrameBuffer *Request::findBuffer(const Stream *stream) const\n>> */\n>> void Request::complete()\n>> {\n>> +\tASSERT(canary_ == REQUEST_CANARY);\n>> \tASSERT(status_ == RequestPending);\n>> \tASSERT(!hasPendingBuffers());\n>> \n>> @@ -289,6 +302,8 @@ void Request::complete()\n>> */\n>> bool Request::completeBuffer(FrameBuffer *buffer)\n>> {\n>> +\tASSERT(canary_ == REQUEST_CANARY);\n>> +\n>> \tLIBCAMERA_TRACEPOINT(request_complete_buffer, this, buffer);\n>> \n>> \tint ret = pending_.erase(buffer);\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id E67EDBD80E\n\tfor ;\n\tMon, 15 Mar 2021 11:24:50 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 3A3B968D3E;\n\tMon, 15 Mar 2021 12:24:50 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id A969860106\n\tfor ;\n\tMon, 15 Mar 2021 12:24:48 +0100 (CET)","from [192.168.0.20]\n\t(cpc89244-aztw30-2-0-cust3082.18-1.cable.virginm.net [86.31.172.11])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 250E5556;\n\tMon, 15 Mar 2021 12:24:48 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"RSNbYt4F\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1615807488;\n\tbh=w3v6RWEqZMYkkSAYxaxmSqoPxDkNjmiNg0qaweY3Kww=;\n\th=Reply-To:Subject:To:Cc:References:From:Date:In-Reply-To:From;\n\tb=RSNbYt4Fs3zBDLGwT6ST1M+LO7BeenSy0sSuRnUDm4mBM3ZdtCED9gBYLTXCp43/0\n\t7E5gY7cBX3WgpMQY53bC070KtFnzKfo6px44+E6YxbeeRmsitjtBZLK269bUW8OJAA\n\tUPga8WqEcY6NhA4C5c+Js8e84oMdzqDjA5PWGDOc=","To":"Laurent Pinchart ","References":"<20210312061131.854849-1-kieran.bingham@ideasonboard.com>\n\t<20210312061131.854849-9-kieran.bingham@ideasonboard.com>\n\t","From":"Kieran Bingham ","Autocrypt":"addr=kieran.bingham@ideasonboard.com; keydata=\n\tmQINBFYE/WYBEACs1PwjMD9rgCu1hlIiUA1AXR4rv2v+BCLUq//vrX5S5bjzxKAryRf0uHat\n\tV/zwz6hiDrZuHUACDB7X8OaQcwhLaVlq6byfoBr25+hbZG7G3+5EUl9cQ7dQEdvNj6V6y/SC\n\trRanWfelwQThCHckbobWiQJfK9n7rYNcPMq9B8e9F020LFH7Kj6YmO95ewJGgLm+idg1Kb3C\n\tpotzWkXc1xmPzcQ1fvQMOfMwdS+4SNw4rY9f07Xb2K99rjMwZVDgESKIzhsDB5GY465sCsiQ\n\tcSAZRxqE49RTBq2+EQsbrQpIc8XiffAB8qexh5/QPzCmR4kJgCGeHIXBtgRj+nIkCJPZvZtf\n\tKr2EAbc6tgg6DkAEHJb+1okosV09+0+TXywYvtEop/WUOWQ+zo+Y/OBd+8Ptgt1pDRyOBzL8\n\tRXa8ZqRf0Mwg75D+dKntZeJHzPRJyrlfQokngAAs4PaFt6UfS+ypMAF37T6CeDArQC41V3ko\n\tlPn1yMsVD0p+6i3DPvA/GPIksDC4owjnzVX9kM8Zc5Cx+XoAN0w5Eqo4t6qEVbuettxx55gq\n\t8K8FieAjgjMSxngo/HST8TpFeqI5nVeq0/lqtBRQKumuIqDg+Bkr4L1V/PSB6XgQcOdhtd36\n\tOe9X9dXB8YSNt7VjOcO7BTmFn/Z8r92mSAfHXpb07YJWJosQOQARAQABtDBLaWVyYW4gQmlu\n\tZ2hhbSA8a2llcmFuLmJpbmdoYW1AaWRlYXNvbmJvYXJkLmNvbT6JAlcEEwEKAEECGwMFCwkI\n\tBwIGFQgJCgsCBBYCAwECHgECF4ACGQEWIQSQLdeYP70o/eNy1HqhHkZyEKRh/QUCXWTtygUJ\n\tCyJXZAAKCRChHkZyEKRh/f8dEACTDsbLN2nioNZMwyLuQRUAFcXNolDX48xcUXsWS2QjxaPm\n\tVsJx8Uy8aYkS85mdPBh0C83OovQR/OVbr8AxhGvYqBs3nQvbWuTl/+4od7DfK2VZOoKBAu5S\n\tQK2FYuUcikDqYcFWJ8DQnubxfE8dvzojHEkXw0sA4igINHDDFX3HJGZtLio+WpEFQtCbfTAG\n\tYZslasz1YZRbwEdSsmO3/kqy5eMnczlm8a21A3fKUo3g8oAZEFM+f4DUNzqIltg31OAB/kZS\n\tenKZQ/SWC8PmLg/ZXBrReYakxXtkP6w3FwMlzOlhGxqhIRNiAJfXJBaRhuUWzPOpEDE9q5YJ\n\tBmqQL2WJm1VSNNVxbXJHpaWMH1sA2R00vmvRrPXGwyIO0IPYeUYQa3gsy6k+En/aMQJd27dp\n\taScf9am9PFICPY5T4ppneeJLif2lyLojo0mcHOV+uyrds9XkLpp14GfTkeKPdPMrLLTsHRfH\n\tfA4I4OBpRrEPiGIZB/0im98MkGY/Mu6qxeZmYLCcgD6qz4idOvfgVOrNh+aA8HzIVR+RMW8H\n\tQGBN9f0E3kfwxuhl3omo6V7lDw8XOdmuWZNC9zPq1UfryVHANYbLGz9KJ4Aw6M+OgBC2JpkD\n\thXMdHUkC+d20dwXrwHTlrJi1YNp6rBc+xald3wsUPOZ5z8moTHUX/uPA/qhGsbkCDQRWBP1m\n\tARAAzijkb+Sau4hAncr1JjOY+KyFEdUNxRy+hqTJdJfaYihxyaj0Ee0P0zEi35CbE6lgU0Uz\n\ttih9fiUbSV3wfsWqg1Ut3/5rTKu7kLFp15kF7eqvV4uezXRD3Qu4yjv/rMmEJbbD4cTvGCYI\n\td6MDC417f7vK3hCbCVIZSp3GXxyC1LU+UQr3fFcOyCwmP9vDUR9JV0BSqHHxRDdpUXE26Dk6\n\tmhf0V1YkspE5St814ETXpEus2urZE5yJIUROlWPIL+hm3NEWfAP06vsQUyLvr/GtbOT79vXl\n\tEn1aulcYyu20dRRxhkQ6iILaURcxIAVJJKPi8dsoMnS8pB0QW12AHWuirPF0g6DiuUfPmrA5\n\tPKe56IGlpkjc8cO51lIxHkWTpCMWigRdPDexKX+Sb+W9QWK/0JjIc4t3KBaiG8O4yRX8ml2R\n\t+rxfAVKM6V769P/hWoRGdgUMgYHFpHGSgEt80OKK5HeUPy2cngDUXzwrqiM5Sz6Od0qw5pCk\n\tNlXqI0W/who0iSVM+8+RmyY0OEkxEcci7rRLsGnM15B5PjLJjh1f2ULYkv8s4SnDwMZ/kE04\n\t/UqCMK/KnX8pwXEMCjz0h6qWNpGwJ0/tYIgQJZh6bqkvBrDogAvuhf60Sogw+mH8b+PBlx1L\n\toeTK396wc+4c3BfiC6pNtUS5GpsPMMjYMk7kVvEAEQEAAYkCPAQYAQoAJgIbDBYhBJAt15g/\n\tvSj943LUeqEeRnIQpGH9BQJdizzIBQkLSKZiAAoJEKEeRnIQpGH9eYgQAJpjaWNgqNOnMTmD\n\tMJggbwjIotypzIXfhHNCeTkG7+qCDlSaBPclcPGYrTwCt0YWPU2TgGgJrVhYT20ierN8LUvj\n\t6qOPTd+Uk7NFzL65qkh80ZKNBFddx1AabQpSVQKbdcLb8OFs85kuSvFdgqZwgxA1vl4TFhNz\n\tPZ79NAmXLackAx3sOVFhk4WQaKRshCB7cSl+RIng5S/ThOBlwNlcKG7j7W2MC06BlTbdEkUp\n\tECzuuRBv8wX4OQl+hbWbB/VKIx5HKlLu1eypen/5lNVzSqMMIYkkZcjV2SWQyUGxSwq0O/sx\n\tS0A8/atCHUXOboUsn54qdxrVDaK+6jIAuo8JiRWctP16KjzUM7MO0/+4zllM8EY57rXrj48j\n\tsbEYX0YQnzaj+jO6kJtoZsIaYR7rMMq9aUAjyiaEZpmP1qF/2sYenDx0Fg2BSlLvLvXM0vU8\n\tpQk3kgDu7kb/7PRYrZvBsr21EIQoIjXbZxDz/o7z95frkP71EaICttZ6k9q5oxxA5WC6sTXc\n\tMW8zs8avFNuA9VpXt0YupJd2ijtZy2mpZNG02fFVXhIn4G807G7+9mhuC4XG5rKlBBUXTvPU\n\tAfYnB4JBDLmLzBFavQfvonSfbitgXwCG3vS+9HEwAjU30Bar1PEOmIbiAoMzuKeRm2LVpmq4\n\tWZw01QYHU/GUV/zHJSFk","Organization":"Ideas on Board","Message-ID":"","Date":"Mon, 15 Mar 2021 11:24:45 +0000","User-Agent":"Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101\n\tThunderbird/68.10.0","MIME-Version":"1.0","In-Reply-To":"","Content-Language":"en-GB","Subject":"Re: [libcamera-devel] [PATCH 8/8] [RFC-Only] libcamera: request: A\n\trequest canary","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Reply-To":"kieran.bingham@ideasonboard.com","Cc":"libcamera devel ","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":15704,"web_url":"https://patchwork.libcamera.org/comment/15704/","msgid":"","date":"2021-03-15T16:28:01","subject":"Re: [libcamera-devel] [PATCH 8/8] [RFC-Only] libcamera: request: A\n\trequest canary","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Kieran,\n\nOn Mon, Mar 15, 2021 at 11:24:45AM +0000, Kieran Bingham wrote:\n> On 14/03/2021 02:13, Laurent Pinchart wrote:\n> > On Fri, Mar 12, 2021 at 06:11:31AM +0000, Kieran Bingham wrote:\n> >> Request objects are created and owned by the application, but are of\n> >> course utilised widely throughout the internals of libcamera.\n> >>\n> >> If the application free's the requests while they are still active\n> >> within libcamera a use after free will occur. While this can be trapped\n> >> by tools such as valgrind, given the importance of this object and the\n> >> relationship of external ownership, it may have some value to provide\n> >> Debug build (disabled at Release build) assertions on the condition of\n> >> these objects.\n> >>\n> >> Make sure the request fails an assertion immediately if used after free.\n> >>\n> >> Signed-off-by: Kieran Bingham \n> >>\n> >> ---\n> >> RFC only, as I was going to dispose of this patch. We added it while\n> >> debugging the IPU3 stability, and it may prove useful to catch errors if\n> >> requests are used after they are released.\n> >>\n> >> However this may be redundant as pipeline handlers should guarantee that\n> >> requests are fully completed when they stop(). Of course the IPU3 wasn't\n> >> meeting that requirement, and we do not have a specific assertion that\n> >> validates that requirement on all pipeline handlers. So perhaps this\n> >> canary might serve as a beneficial guard?\n> > \n> > I think we should move that check from the IPU3 pipeline handler to the\n> > core, as commented on the corresponding patch, so this patch wouldn't\n> > really be needed.\n> > \n> >> If not, at least posting it will mean it can be used in the future if it\n> >> comes up again, or the concept could be applied to other objects if\n> >> appropriate.\n> >>\n> >> include/libcamera/request.h | 2 ++\n> >> src/libcamera/request.cpp | 15 +++++++++++++++\n> >> 2 files changed, 17 insertions(+)\n> >>\n> >> diff --git a/include/libcamera/request.h b/include/libcamera/request.h\n> >> index 59d7f4bac0d2..fc56d63c8c67 100644\n> >> --- a/include/libcamera/request.h\n> >> +++ b/include/libcamera/request.h\n> >> @@ -78,6 +78,8 @@ private:\n> >> \tconst uint64_t cookie_;\n> >> \tStatus status_;\n> >> \tbool cancelled_;\n> >> +\n> >> +\tint canary_;\n> > \n> > If we want to do this, couldn't we add a RequestFreed status to avoid\n> > adding a separate field ?\n> \n> It's tempting to add/handle this to the state machine indeed, but we are\n> limited on the guarantees we can make there.\n> \n> After a free - we can't guarantee that Request->status() == RequestFreed :-)\n\nCan't we, if we set status_ to RequestFreed in the destructor ? If\nyou're concerned that someone would override the status, you could add\nan assertion in setStatus().\n\n> The point of the canary is to assert that it has not been free'd and\n> that the values match exactly.\n> \n> Maybe a RequestFreed state will add some protection though - but as this\n> is RFC only - we can leave it to think about if we end up digging in\n> here again.\n\nSounds good to me.\n\n> >> };\n> >> \n> >> } /* namespace libcamera */\n> >> diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp\n> >> index 12c2e7d425f9..83169a11e1e5 100644\n> >> --- a/src/libcamera/request.cpp\n> >> +++ b/src/libcamera/request.cpp\n> >> @@ -18,6 +18,8 @@\n> >> #include \"libcamera/internal/log.h\"\n> >> #include \"libcamera/internal/tracepoints.h\"\n> >> \n> >> +#define REQUEST_CANARY 0x1F2E3D4C\n> >> +\n> >> /**\n> >> * \\file request.h\n> >> * \\brief Describes a frame capture request to be processed by a camera\n> >> @@ -89,6 +91,8 @@ Request::Request(Camera *camera, uint64_t cookie)\n> >> \n> >> \tLIBCAMERA_TRACEPOINT(request_construct, this);\n> >> \n> >> +\tcanary_ = REQUEST_CANARY;\n> >> +\n> >> \tLOG(Request, Debug) << \"Created request - cookie: \" << cookie_;\n> >> }\n> >> \n> >> @@ -99,6 +103,8 @@ Request::~Request()\n> >> \tdelete metadata_;\n> >> \tdelete controls_;\n> >> \tdelete validator_;\n> >> +\n> >> +\tcanary_ = 0;\n> >> }\n> >> \n> >> /**\n> >> @@ -113,6 +119,8 @@ Request::~Request()\n> >> */\n> >> void Request::reuse(ReuseFlag flags)\n> >> {\n> >> +\tASSERT(canary_ == REQUEST_CANARY);\n> >> +\n> >> \tLIBCAMERA_TRACEPOINT(request_reuse, this);\n> >> \n> >> \tpending_.clear();\n> >> @@ -176,6 +184,8 @@ void Request::reuse(ReuseFlag flags)\n> >> */\n> >> int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)\n> >> {\n> >> +\tASSERT(canary_ == REQUEST_CANARY);\n> >> +\n> >> \tif (!stream) {\n> >> \t\tLOG(Request, Error) << \"Invalid stream reference\";\n> >> \t\treturn -EINVAL;\n> >> @@ -211,6 +221,8 @@ int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)\n> >> */\n> >> FrameBuffer *Request::findBuffer(const Stream *stream) const\n> >> {\n> >> +\tASSERT(canary_ == REQUEST_CANARY);\n> >> +\n> >> \tconst auto it = bufferMap_.find(stream);\n> >> \tif (it == bufferMap_.end())\n> >> \t\treturn nullptr;\n> >> @@ -262,6 +274,7 @@ FrameBuffer *Request::findBuffer(const Stream *stream) const\n> >> */\n> >> void Request::complete()\n> >> {\n> >> +\tASSERT(canary_ == REQUEST_CANARY);\n> >> \tASSERT(status_ == RequestPending);\n> >> \tASSERT(!hasPendingBuffers());\n> >> \n> >> @@ -289,6 +302,8 @@ void Request::complete()\n> >> */\n> >> bool Request::completeBuffer(FrameBuffer *buffer)\n> >> {\n> >> +\tASSERT(canary_ == REQUEST_CANARY);\n> >> +\n> >> \tLIBCAMERA_TRACEPOINT(request_complete_buffer, this, buffer);\n> >> \n> >> \tint ret = pending_.erase(buffer);","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id BDDF6BD80C\n\tfor ;\n\tMon, 15 Mar 2021 16:28:40 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id CA07268D3F;\n\tMon, 15 Mar 2021 17:28:39 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id B767A68D3E\n\tfor ;\n\tMon, 15 Mar 2021 17:28:37 +0100 (CET)","from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi\n\t[62.78.145.57])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 21B20316;\n\tMon, 15 Mar 2021 17:28:37 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"rJgGadL3\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1615825717;\n\tbh=6IsMWe4C7BAkr2XLmWTFymuDcIewm45LHSou4icHRvE=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=rJgGadL3WD/z9pF1ZrqrPUiXSEVsyMtxnI+v8pWOHAkKjw4EwKmCxd28ZmqZxR3mB\n\teblOaY27oAAjOT8khnKSAY+SDbMF/s4P1BH7+WC6eQK7lAGRynU/z+BH1zY3VFBQZE\n\tqp14l/JFyf6v743BxgWl4++Cp8uK1gryturXBTtw=","Date":"Mon, 15 Mar 2021 18:28:01 +0200","From":"Laurent Pinchart ","To":"Kieran Bingham ","Message-ID":"","References":"<20210312061131.854849-1-kieran.bingham@ideasonboard.com>\n\t<20210312061131.854849-9-kieran.bingham@ideasonboard.com>\n\t\n\t","MIME-Version":"1.0","Content-Disposition":"inline","In-Reply-To":"","Subject":"Re: [libcamera-devel] [PATCH 8/8] [RFC-Only] libcamera: request: A\n\trequest canary","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Cc":"libcamera devel ","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":15707,"web_url":"https://patchwork.libcamera.org/comment/15707/","msgid":"<8f0b42a0-846d-ec6d-6516-e5f5ae700e53@ideasonboard.com>","date":"2021-03-15T16:44:13","subject":"Re: [libcamera-devel] [PATCH 8/8] [RFC-Only] libcamera: request: A\n\trequest canary","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"Hi Laurent,\n\nOn 15/03/2021 16:28, Laurent Pinchart wrote:\n> Hi Kieran,\n> \n> On Mon, Mar 15, 2021 at 11:24:45AM +0000, Kieran Bingham wrote:\n>> On 14/03/2021 02:13, Laurent Pinchart wrote:\n>>> On Fri, Mar 12, 2021 at 06:11:31AM +0000, Kieran Bingham wrote:\n>>>> Request objects are created and owned by the application, but are of\n>>>> course utilised widely throughout the internals of libcamera.\n>>>>\n>>>> If the application free's the requests while they are still active\n>>>> within libcamera a use after free will occur. While this can be trapped\n>>>> by tools such as valgrind, given the importance of this object and the\n>>>> relationship of external ownership, it may have some value to provide\n>>>> Debug build (disabled at Release build) assertions on the condition of\n>>>> these objects.\n>>>>\n>>>> Make sure the request fails an assertion immediately if used after free.\n>>>>\n>>>> Signed-off-by: Kieran Bingham \n>>>>\n>>>> ---\n>>>> RFC only, as I was going to dispose of this patch. We added it while\n>>>> debugging the IPU3 stability, and it may prove useful to catch errors if\n>>>> requests are used after they are released.\n>>>>\n>>>> However this may be redundant as pipeline handlers should guarantee that\n>>>> requests are fully completed when they stop(). Of course the IPU3 wasn't\n>>>> meeting that requirement, and we do not have a specific assertion that\n>>>> validates that requirement on all pipeline handlers. So perhaps this\n>>>> canary might serve as a beneficial guard?\n>>>\n>>> I think we should move that check from the IPU3 pipeline handler to the\n>>> core, as commented on the corresponding patch, so this patch wouldn't\n>>> really be needed.\n>>>\n>>>> If not, at least posting it will mean it can be used in the future if it\n>>>> comes up again, or the concept could be applied to other objects if\n>>>> appropriate.\n>>>>\n>>>> include/libcamera/request.h | 2 ++\n>>>> src/libcamera/request.cpp | 15 +++++++++++++++\n>>>> 2 files changed, 17 insertions(+)\n>>>>\n>>>> diff --git a/include/libcamera/request.h b/include/libcamera/request.h\n>>>> index 59d7f4bac0d2..fc56d63c8c67 100644\n>>>> --- a/include/libcamera/request.h\n>>>> +++ b/include/libcamera/request.h\n>>>> @@ -78,6 +78,8 @@ private:\n>>>> \tconst uint64_t cookie_;\n>>>> \tStatus status_;\n>>>> \tbool cancelled_;\n>>>> +\n>>>> +\tint canary_;\n>>>\n>>> If we want to do this, couldn't we add a RequestFreed status to avoid\n>>> adding a separate field ?\n>>\n>> It's tempting to add/handle this to the state machine indeed, but we are\n>> limited on the guarantees we can make there.\n>>\n>> After a free - we can't guarantee that Request->status() == RequestFreed :-)\n> \n> Can't we, if we set status_ to RequestFreed in the destructor ? If\n> you're concerned that someone would override the status, you could add\n> an assertion in setStatus().\n\nNo, we simply can't trust status after the request has been freed.\n\nThat's the point I was making above. Asserting in setStatus() is\nirrelevant because the case I'm referring to, the memory is not going to\nbe changed through the Request interface.\n\n\nNote that the canary asserts a variable IS a single specific value while\nit's valid.\n\nSetting the Request->status_ == RequestFreed, means that we have to\nassert that it 'is not' that value. (Or we assert that it's one of the\nvalid states of course, but that's an ever so slightly larger scope/risk\nof false positives).\n\n\nOnce the object is free'd the memory may as well be considered volatile,\nand changeable to anything else. That memory is no longer owned.\n\nSo then - this would merrilly pass along the way...\n\n Request R = new(Request);\n\n pipelinehandler->queueRequest(R);\n\n delete(R);\t/* This is not allowed, hence the assertion below */\n\n MyObject = new(object);\n /* Same memory occupied by R is now MyObject */\n\n (meanwhile... over in the pipeline handler)\n ASSERT(Request->status != RequestFreed);\n /* Passed because Request->status == random value in MyObject */\n\n\nWe can handle this by asserting that the request status is in a valid\nstate of course, but that's slightly different.\n\n\n\n\n>> The point of the canary is to assert that it has not been free'd and\n>> that the values match exactly.\n>>\n>> Maybe a RequestFreed state will add some protection though - but as this\n>> is RFC only - we can leave it to think about if we end up digging in\n>> here again.\n> \n> Sounds good to me.\n> \n>>>> };\n>>>> \n>>>> } /* namespace libcamera */\n>>>> diff --git a/src/libcamera/request.cpp b/src/libcamera/request.cpp\n>>>> index 12c2e7d425f9..83169a11e1e5 100644\n>>>> --- a/src/libcamera/request.cpp\n>>>> +++ b/src/libcamera/request.cpp\n>>>> @@ -18,6 +18,8 @@\n>>>> #include \"libcamera/internal/log.h\"\n>>>> #include \"libcamera/internal/tracepoints.h\"\n>>>> \n>>>> +#define REQUEST_CANARY 0x1F2E3D4C\n>>>> +\n>>>> /**\n>>>> * \\file request.h\n>>>> * \\brief Describes a frame capture request to be processed by a camera\n>>>> @@ -89,6 +91,8 @@ Request::Request(Camera *camera, uint64_t cookie)\n>>>> \n>>>> \tLIBCAMERA_TRACEPOINT(request_construct, this);\n>>>> \n>>>> +\tcanary_ = REQUEST_CANARY;\n>>>> +\n>>>> \tLOG(Request, Debug) << \"Created request - cookie: \" << cookie_;\n>>>> }\n>>>> \n>>>> @@ -99,6 +103,8 @@ Request::~Request()\n>>>> \tdelete metadata_;\n>>>> \tdelete controls_;\n>>>> \tdelete validator_;\n>>>> +\n>>>> +\tcanary_ = 0;\n>>>> }\n>>>> \n>>>> /**\n>>>> @@ -113,6 +119,8 @@ Request::~Request()\n>>>> */\n>>>> void Request::reuse(ReuseFlag flags)\n>>>> {\n>>>> +\tASSERT(canary_ == REQUEST_CANARY);\n>>>> +\n>>>> \tLIBCAMERA_TRACEPOINT(request_reuse, this);\n>>>> \n>>>> \tpending_.clear();\n>>>> @@ -176,6 +184,8 @@ void Request::reuse(ReuseFlag flags)\n>>>> */\n>>>> int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)\n>>>> {\n>>>> +\tASSERT(canary_ == REQUEST_CANARY);\n>>>> +\n>>>> \tif (!stream) {\n>>>> \t\tLOG(Request, Error) << \"Invalid stream reference\";\n>>>> \t\treturn -EINVAL;\n>>>> @@ -211,6 +221,8 @@ int Request::addBuffer(const Stream *stream, FrameBuffer *buffer)\n>>>> */\n>>>> FrameBuffer *Request::findBuffer(const Stream *stream) const\n>>>> {\n>>>> +\tASSERT(canary_ == REQUEST_CANARY);\n>>>> +\n>>>> \tconst auto it = bufferMap_.find(stream);\n>>>> \tif (it == bufferMap_.end())\n>>>> \t\treturn nullptr;\n>>>> @@ -262,6 +274,7 @@ FrameBuffer *Request::findBuffer(const Stream *stream) const\n>>>> */\n>>>> void Request::complete()\n>>>> {\n>>>> +\tASSERT(canary_ == REQUEST_CANARY);\n>>>> \tASSERT(status_ == RequestPending);\n>>>> \tASSERT(!hasPendingBuffers());\n>>>> \n>>>> @@ -289,6 +302,8 @@ void Request::complete()\n>>>> */\n>>>> bool Request::completeBuffer(FrameBuffer *buffer)\n>>>> {\n>>>> +\tASSERT(canary_ == REQUEST_CANARY);\n>>>> +\n>>>> \tLIBCAMERA_TRACEPOINT(request_complete_buffer, this, buffer);\n>>>> \n>>>> \tint ret = pending_.erase(buffer);\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id BEAE4BD80C\n\tfor ;\n\tMon, 15 Mar 2021 16:44:18 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 377C668D46;\n\tMon, 15 Mar 2021 17:44:18 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id DE82268D3E\n\tfor ;\n\tMon, 15 Mar 2021 17:44:16 +0100 (CET)","from [192.168.0.20]\n\t(cpc89244-aztw30-2-0-cust3082.18-1.cable.virginm.net [86.31.172.11])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 5061A316;\n\tMon, 15 Mar 2021 17:44:16 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com;\n\tdkim=fail reason=\"signature verification failed\" (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"jNV4ltnF\"; 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Linux x86_64; rv:68.0) Gecko/20100101\n\tThunderbird/68.10.0","MIME-Version":"1.0","In-Reply-To":"","Content-Language":"en-GB","Subject":"Re: [libcamera-devel] [PATCH 8/8] [RFC-Only] libcamera: request: A\n\trequest canary","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Reply-To":"kieran.bingham@ideasonboard.com","Cc":"libcamera devel ","Content-Type":"text/plain; charset=\"us-ascii\"","Content-Transfer-Encoding":"7bit","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]