[Bug 16193] New: NULL pointer dereference - radeon_unmap_vram_bos+0x22/0x50

[Bug 16193] New: NULL pointer dereference - radeon_unmap_vram_bos+0x22/0x50

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=16193

           Summary: NULL pointer dereference -
                    radeon_unmap_vram_bos+0x22/0x50
           Product: Drivers
           Version: 2.5
    Kernel Version: 2.6.35-rc3
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
        AssignedTo: drivers_video-dri@kernel-bugs.osdl.org
        ReportedBy: bugz.kernel.tormod@xoxy.net
        Regression: No


I was testing the game Lugaro on M26 (RV410), switching between different
resolutions in the game's options menu. The LCD native 1680x1050 made the game
cursor very slow, so I chose 1400x1050 (have to quit the game and reenter to
take effect). After that I could not go back to 1024x768 (default, works well),
only 1400++ resolutions were listed. Then suddenly X froze, but sysrq-B worked.

I am not sure if this is a recent regression, because it is the first time I
try out different resolutions in this game, and the issue might not be easy to
reproduce as it happened after a series of resolution switching.

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[Bug 16193] NULL pointer dereference - radeon_unmap_vram_bos+0x22/0x50

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=16193





--- Comment #1 from Tormod Volden <bugz.kernel.tormod@xoxy.net>  2010-06-13 12:40:50 ---
BTW, I was using mesa classic from git.

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[Bug 16193] NULL pointer dereference - radeon_unmap_vram_bos+0x22/0x50

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=16193


Alan <alan@lxorguk.ukuu.org.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |alan@lxorguk.ukuu.org.uk




--- Comment #2 from Alan <alan@lxorguk.ukuu.org.uk>  2012-11-05 14:16:22 ---
Closing as obsolete. If this is still seen on modern kernels (3.2+) please
update/reopen

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[Bug 16193] NULL pointer dereference - radeon_unmap_vram_bos+0x22/0x50

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=16193


Alan <alan@lxorguk.ukuu.org.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |OBSOLETE




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[Bug 16193] NULL pointer dereference - radeon_unmap_vram_bos+0x22/0x50

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=16193

Scott Wood <scott@buserror.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |scott@buserror.net

--- Comment #3 from Scott Wood <scott@buserror.net> ---
I saw this (or something very similar) on Ubuntu's 3.8.0-27 kernel (but I hope
this is useful information anyway -- I doubt it's an Ubuntu issue, and this
code doesn't appear to have changed since 3.8), when using alt-enter to toggle
fullscreen in dosbox (which worked many times in the past, so it's not easily
reproduceable).

The NULL pointer is in rdev->gem.objects.  I notice that elsewhere,
rdev->gem.mutex is held when the list is modified, but it does not appear to be
held when traversed in radeon_unmap_vram_bos().  Will ttm_bo_unmap_virtual()
ever acquire gem.mutex itself (i.e. can bo->destroy() be called)?  It wasn't
immediately obvious that it would from reading the code, but if
ttm_bo_unmap_virtual() can't cause list entry deletion then why use
list_for_each_entry_safe()?  Is there something else that ensures that the list
won't be modified concurrently with radeon_unmap_vram_bos()?

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