525895ba38
Due to a race it was possible for a fence to be destroyed while another thread was trying to synchronise with it. If this happened in the fallback non-semaphore path, it lead to the following oops due to fence->channel being NULL. BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<fa9632ce>] nouveau_fence_update+0xe/0xe0 [nouveau] *pde = a649c067 SMP Modules linked in: fuse nouveau(O) ttm(O) drm_kms_helper(O) drm(O) mxm_wmi video wmi netconsole configfs lockd bnep bluetooth rfkill ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 xt_state nf_conntrack ip6table_filter ip6_tables snd_hda_codec_realtek snd_hda_intel snd_hda_cobinfmt_misc uinput ata_generic pata_acpi pata_aet2c_algo_bit i2c_core [last unloaded: wmi] Pid: 2255, comm: gnome-shell Tainted: G O 3.2.0-0.rc5.git0.1.fc17.i686 #1 System manufacturer System Product Name/M2A-VM EIP: 0060:[<fa9632ce>] EFLAGS: 00010296 CPU: 1 EIP is at nouveau_fence_update+0xe/0xe0 [nouveau] EAX: 00000000 EBX: ddfc6dd0 ECX: dd111580 EDX: 00000000 ESI: 00003e80 EDI: dd111580 EBP: dd121d00 ESP: dd121ce8 DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 Process gnome-shell (pid: 2255, ti=dd120000 task=dd111580 task.ti=dd120000) Stack: 7dc86c76 00000000 00003e80 ddfc6dd0 00003e80 dd111580 dd121d0c fa96371f 00000000 dd121d3c fa963773 dd111580 01000246 000ec53d 00000000 ddfc6dd0 00001f40 00000000 ddfc6dd0 00000010 dc7df840 dd121d6c fa9639a0 00000000 Call Trace: [<fa96371f>] __nouveau_fence_signalled+0x1f/0x30 [nouveau] [<fa963773>] __nouveau_fence_wait+0x43/0xd0 [nouveau] [<fa9639a0>] nouveau_fence_sync+0x1a0/0x1c0 [nouveau] [<fa964046>] validate_list+0x176/0x300 [nouveau] [<f7d9c9c0>] ? ttm_bo_mem_put+0x30/0x30 [ttm] [<fa964b8a>] nouveau_gem_ioctl_pushbuf+0x48a/0xfd0 [nouveau] [<c0406481>] ? die+0x31/0x80 [<f7c93d98>] drm_ioctl+0x388/0x490 [drm] [<c0406481>] ? die+0x31/0x80 [<fa964700>] ? nouveau_gem_ioctl_new+0x150/0x150 [nouveau] [<c0635c7b>] ? file_has_perm+0xcb/0xe0 [<f7c93a10>] ? drm_copy_field+0x80/0x80 [drm] [<c0564f56>] do_vfs_ioctl+0x86/0x5b0 [<c0406481>] ? die+0x31/0x80 [<c0635f22>] ? selinux_file_ioctl+0x62/0x130 [<c0554f30>] ? fget_light+0x30/0x340 [<c05654ef>] sys_ioctl+0x6f/0x80 [<c099e3a4>] syscall_call+0x7/0xb [<c0406481>] ? die+0x31/0x80 [<c0406481>] ? die+0x31/0x80 Signed-off-by: Ben Skeggs <bskeggs@redhat.com> Cc: stable@vger.kernel.org
************************************************************
* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
************************************************************
The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://dri.freedesktop.org/wiki/Documentation
http://sourceforge.net/project/showfiles.php?group_id=387
http://dri.sourceforge.net/doc/
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://dri.sourceforge.net/doc/drm_low_level.html
Hardware Locking for the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/hardware_locking_low_level.html
A Security Analysis of the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/security_low_level.html