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Janusz Krzysztofik 4462966a93 drm/i915: Fix potential UAF in TTM object purge
TLDR: The bo->ttm object might be changed by calling ttm_bo_validate(),
      move casting it to an i915_tt object later to actually get the right
      pointer.

A user reported hitting the following bug under heavy use on DG2:

[26620.095550] Oops: general protection fault, probably for non-canonical address 0xa56b6b6b6b6b6b8b: 0000 1 SMP NOPTI
[26620.095556] CPU: 2 UID: 0 PID: 631 Comm: Xorg Not tainted 6.18.8 #1 PREEMPT(lazy)
[26620.095558] Hardware name: ASRock B850M Steel Legend WiFi/B850M Steel Legend WiFi, BIOS 3.50 09/18/2025
[26620.095559] RIP: 0010:i915_ttm_purge+0x84/0x100 [i915]
[26620.095604] Code: 00 00 00 48 8d 54 24 10 48 89 e6 48 89 fb e8 83 aa ae ff 85 c0 75 6f 48 83 bb a8 01 00 00 00 74 2c 48 8b 45 78 48 85 c0 74 23 <48> 8b 78 20 48 c7 c2 ff ff ff ff 31 f6 e8 7a 73 e3 e0 48 8b 7d 78
[26620.095605] RSP: 0018:ffffc90005fd7430 EFLAGS: 00010282
[26620.095607] RAX: a56b6b6b6b6b6b6b RBX: ffff8881f46c3dc0 RCX: 0000000000000000
[26620.095608] RDX: 0000000000000000 RSI: 0000000000000246 RDI: 00000000ffffffff
[26620.095609] RBP: ffff888289610f00 R08: 0000000000000001 R09: ffff88823b022000
[26620.095609] R10: ffff888103029b28 R11: ffff8881fc7f3800 R12: ffff88810b6150d0
[26620.095609] R13: ffff888289610f00 R14: 0000000000000000 R15: ffff8881f46c3dc0
[26620.095610] FS: 00007f1004d86900(0000) GS:ffff88901c858000(0000) knlGS:0000000000000000
[26620.095611] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[26620.095611] CR2: 00007f0fdf489000 CR3: 000000035b0c1000 CR4: 0000000000750ef0
[26620.095612] PKRU: 55555554
[26620.095612] Call Trace:
[26620.095615] <TASK>
[26620.095615] i915_ttm_move+0x2b9/0x420 [i915]
[26620.095642] ? ttm_tt_init+0x65/0x80 [ttm]
[26620.095644] ? i915_ttm_tt_create+0xc6/0x150 [i915]
[26620.095667] ttm_bo_handle_move_mem+0xb6/0x160 [ttm]
[26620.095669] ttm_bo_evict+0x100/0x150 [ttm]
[26620.095671] ? preempt_count_add+0x64/0xa0
[26620.095673] ? _raw_spin_lock+0xe/0x30
[26620.095675] ? _raw_spin_unlock+0xd/0x30
[26620.095675] ? i915_gem_object_evictable+0xb7/0xd0 [i915]
[26620.095704] ttm_bo_evict_cb+0x6e/0xd0 [ttm]
[26620.095705] ttm_lru_walk_for_evict+0xa6/0x200 [ttm]
[26620.095708] ttm_bo_alloc_resource+0x185/0x4f0 [ttm]
[26620.095709] ? init_object+0x62/0xd0
[26620.095712] ttm_bo_validate+0x7a/0x180 [ttm]
[26620.095713] ? _raw_spin_unlock_irqrestore+0x16/0x30
[26620.095714] __i915_ttm_get_pages+0xb0/0x170 [i915]
[26620.095737] i915_ttm_get_pages+0x9f/0x150 [i915]
[26620.095759] ? i915_gem_do_execbuffer+0xedc/0x2b40 [i915]
[26620.095786] ? alloc_debug_processing+0xd0/0x100
[26620.095787] ? _raw_spin_unlock_irqrestore+0x16/0x30
[26620.095788] ? i915_vma_instance+0xa0/0x4e0 [i915]
[26620.095822] __i915_gem_object_get_pages+0x2f/0x40 [i915]
[26620.095848] i915_vma_pin_ww+0x706/0x980 [i915]
[26620.095875] ? i915_gem_do_execbuffer+0xedc/0x2b40 [i915]
[26620.095904] eb_validate_vmas+0x170/0xa00 [i915]
[26620.095930] i915_gem_do_execbuffer+0x1201/0x2b40 [i915]
[26620.095953] ? alloc_debug_processing+0xd0/0x100
[26620.095954] ? _raw_spin_unlock_irqrestore+0x16/0x30
[26620.095955] ? i915_gem_execbuffer2_ioctl+0xc9/0x240 [i915]
[26620.095977] ? __wake_up_sync_key+0x32/0x50
[26620.095979] ? i915_gem_execbuffer2_ioctl+0xc9/0x240 [i915]
[26620.096001] ? __slab_alloc.isra.0+0x67/0xc0
[26620.096003] i915_gem_execbuffer2_ioctl+0x11a/0x240 [i915]

Results from decode_stacktrace.sh pointed to dereference of a file pointer
field of a i915 TTM page vector container associated with an object being
purged on eviction.  That path is taken when the object is marked as no
longer needed.

Code analysis revealed a possibility of the i915 TTM page vector container
being replaced with a new instance inside a function that purges content
of the object, should it be still busy.  That function is called,
indirectly via a more general function that changes the object's placement
and caching policy, before the problematic dereference, but still after
a pointer to the container is captured, rendering the pointer no longer
valid.

Fix the issue by capturing the pointer to the container only after its
potential replacement.

v2: Move the container_of() inside the if block (Sebastian),
  - a simplified version of the commit description that explains briefly
    why the change is necessary (Christian).

Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/work_items/14882
Fixes: 7ae034590c ("drm/i915/ttm: add tt shmem backend")
Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik@linux.intel.com>
Cc: stable@vger.kernel.org # v5.17+
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Sebastian Brzezinka <sebastian.brzezinka@intel.com>
Cc: Christian König <christian.koenig@amd.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://lore.kernel.org/r/20260508122612.469227-2-janusz.krzysztofik@linux.intel.com
2026-05-19 11:53:26 +02:00
arch sh fixes for v7.1 2026-05-03 08:58:42 -07:00
block block: only restrict bio allocation gfp mask asked to block 2026-04-21 11:42:12 -06:00
certs Clang build fixes for 7.1 2026-04-24 09:29:51 -07:00
crypto This push contains the following changes: 2026-05-02 12:31:43 -07:00
Documentation drm-misc-next for v7.2-rc1: 2026-05-08 14:16:04 +10:00
drivers drm/i915: Fix potential UAF in TTM object purge 2026-05-19 11:53:26 +02:00
fs Description for this pull request: 2026-05-02 12:25:57 -07:00
include drm-misc-next for v7.2-rc1: 2026-05-08 14:16:04 +10:00
init memblock: updates for 7.0-rc1 2026-04-18 11:29:14 -07:00
io_uring io_uring-7.1-20260430 2026-05-01 11:01:31 -07:00
ipc Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
kernel Fix lockup in requeue-PI during signal/timeout wakeups, 2026-05-03 08:17:09 -07:00
lib 20 hotfixes. All are for MM (and for MMish maintainers). 9 are cc:stable 2026-05-01 08:45:23 -07:00
LICENSES LICENSES: Add modern form of the LGPL-2.1 tags to the usage guide section 2025-10-22 07:58:19 +02:00
mm slab fixes for 7.1-rc1 2026-05-03 08:19:57 -07:00
net net/sched: cls_flower: revert unintended changes 2026-04-30 13:47:01 +02:00
rust Char/Misc/IIO/and others driver updates for 7.1-rc1 2026-04-24 13:23:50 -07:00
samples soc: drivers for 7.1 2026-04-16 20:34:34 -07:00
scripts First round of Kbuild fixes for 7.1 2026-04-25 17:04:15 -07:00
security selinux: fix avdcache auditing 2026-04-28 18:13:58 -04:00
sound ALSA: hda/tas2781: Fix incorrect bit update for non-book-zero or book 0 pages >1 2026-04-29 07:51:17 +02:00
tools Assorted arm64, ACPI and kselftest fixes for 7.1-rc2: 2026-05-01 16:32:42 -07:00
usr kbuild: uapi: also test UAPI headers against C++ compilers 2026-03-25 13:24:42 +01:00
virt Arm: 2026-04-17 07:18:03 -07:00
.clang-format Devicetree updates for v7.0: 2026-02-11 18:27:08 -08:00
.clippy.toml rust: bump Clippy's MSRV and clean incompatible_msrv allows 2026-04-07 09:51:39 +02:00
.cocciconfig
.editorconfig editorconfig: add rst extension 2026-01-26 19:07:09 -08:00
.get_maintainer.ignore .get_maintainer.ignore: add myself 2026-04-02 16:48:25 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rust: provide an option to inline C helpers into Rust 2026-03-30 02:03:52 +02:00
.mailmap drm fixes for 7.1-rc2 2026-05-01 16:56:08 -07:00
.pylintrc docs: Move the python libraries to tools/lib/python 2025-11-18 09:22:40 -07:00
.rustfmt.toml
COPYING
CREDITS Delete some obsolete networking code 2026-04-24 09:41:58 -07:00
Kbuild checksyscalls: move instance functionality into generic code 2026-04-05 09:21:32 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS drm-misc-next for v7.2-rc1: 2026-05-08 14:16:04 +10:00
Makefile Linux 7.1-rc2 2026-05-03 14:21:25 -07:00
README docs: add AI Coding Assistants documentation 2026-01-06 14:55:06 -07:00

Linux kernel
============

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-----------

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--------------------

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