Linux mutex leak in drm_dp_get_mst_branch
PATCH 1/1 Linux mutex leak in drm_dp_get_mst_branch
https://bugs.freedesktop.org/show_bug.cgi?id=92480
Bug ID: 92480
Summary: [Patch] Linux mutex leak in drm_dp_get_mst_branch
Product: DRI
Version: unspecified
Hardware: x86-64 (AMD64)
OS: Linux (All)
Status: NEW
Severity: normal
Priority: medium
Component: General
Assignee: [email protected]
Reporter: [email protected]
I believe I have found a mutex leak in drm_dp_get_mst_branch_device() in linux/drivers/gpu/drm/drm_dp_mst_topology.c in kernels 4.2-rc1 through the current version, 4.3-rc5, where the function can take an error exit without doing mutex_unlock(&mgr_lock). I have attached a proposed patch.
Unfortunately, since I made the patch, I have not been able to trigger the error branch that the patch fixes, but I did find the bug by observing that error branch executing and printing an error message that I believe is unique to that branch ("*ERROR* failed to lookup MSTB"):
[ 36.944273] [drm:gen8_irq_handler [i915]] *ERROR* The master control interrupt lied (SDE)! [ 74.576811] [drm:drm_dp_get_mst_branch_device [drm_kms_helper]] *ERROR* failed to lookup MSTB with lct 2, rad 10 [ 74.587704] BUG: workqueue leaked lock or atomic: kworker/u8:0/0x00000000/6 [ 74.587704] last function: i915_digport_work_func [i915] [ 74.655752] [drm:gen8_irq_handler [i915]] *ERROR* The master control
interrupt lied (SDE)!
I think this patch is also arguably an infinitesimal improvement in that it depends less on the optimizer, by reducing two references to port->mstb to one.
Anyhow, if the patch looks good, I would be delighted to if the appropriate person (Dave?) would integrate it for submission upstream.
Thanks in advance for any feedback on this.
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PATCH 1/1 Linux mutex leak in drm_dp_get_mst_branch
https://bugs.freedesktop.org/show_bug.cgi?id=92480
--- Comment #1 from Adam J. Richter <[email protected]> --- Created attachment 118904
--> https://bugs.freedesktop.org/attachment.cgi?id=118904&action=edit
Patch to fix mutex leak on error return of drm_dp_get_mst_branch_device in linux-4.3-rc5/drivers/gpu/drm/drm_dp_mst_topology.c
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PATCH 1/1 Linux mutex leak in drm_dp_get_mst_branch
In reply to [email protected]https://bugs.freedesktop.org/show_bug.cgi?id=92480
--- Comment #2 from Jani Nikula <[email protected]> --- Please send your (In reply to Adam J. Richter from comment #0)
Quoted 2 lines
Anyhow, if the patch looks good, I would be delighted to if the appropriate person (Dave?) would integrate it for submission upstream.
Good catch!
Please send the patch in proper patch format with your Signed-off-by to [email protected] mailing list. See Documentation/SubmittingPatches for help.
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PATCH 1/1 Linux mutex leak in drm_dp_get_mst_branch
In reply to [email protected]https://bugs.freedesktop.org/show_bug.cgi?id=92480
Jani Nikula <[email protected]> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED--- Comment #3 from Jani Nikula <[email protected]> --- commit 6749c9f023d49adca3ca4773e93282b95ceebfb5
Author: Adam Richter <[email protected]> Date: Fri Oct 16 03:33:02 2015 -0700
drm: fix mutex leak in drm_dp_get_mst_branch_device
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PATCH 1/1 Linux mutex leak in drm_dp_get_mst_branch
In reply to [email protected]https://bugs.freedesktop.org/show_bug.cgi?id=92480
--- Comment #4 from Jani Nikula <[email protected]> --- also cherry-picked to v4.3 as
commit 30730c7f5943b3beace1e29f7f1476e05de3da14
Author: Adam Richter <[email protected]> Date: Fri Oct 16 03:33:02 2015 -0700
drm: fix mutex leak in drm_dp_get_mst_branch_device
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