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drm/ttm: Fix bo resource use-after-free
authorThadeu Lima de Souza Cascardo <cascardo@igalia.com>
Wed, 4 Mar 2026 23:27:52 +0000 (20:27 -0300)
committerTvrtko Ursulin <tursulin@ursulin.net>
Thu, 5 Mar 2026 08:12:36 +0000 (08:12 +0000)
When allocating a lot of buffers and putting the TTM under memory pressure,
during swapout, it might crash the system with the stack trace below.

It turns out that ttm_bo_swapout_cb might replace bo->resource when it
moves it to system cached.

When commit c06da4b3573a ("drm/ttm: Tidy usage of local variables a little
bit") used a local variable for bo->resource, it used the freed resource
later in the function, leading to a UAF.

Move back to using bo->resource in all cases in that function instead of a
local variable.

[  604.814275] BUG: kernel NULL pointer dereference, address: 0000000000000000
[  604.814284] #PF: supervisor read access in kernel mode
[  604.814288] #PF: error_code(0x0000) - not-present page
[  604.814291] PGD 0 P4D 0
[  604.814296] Oops: Oops: 0000 [#1] SMP NOPTI
[  604.814303] CPU: 2 UID: 0 PID: 4408 Comm: vulkan Tainted: G        W           7.0.0-rc2-00001-gc50a051e6aca #21 PREEMPT(full)  aef6eb0c02036a7c8a5e62e0c84a30c2be90688d
[  604.814309] Tainted: [W]=WARN
[  604.814311] Hardware name: Valve Jupiter/Jupiter, BIOS F7A0133 08/05/2024
[  604.814314] RIP: 0010:ttm_resource_move_to_lru_tail+0x100/0x160 [ttm]
[  604.814329] Code: 5b 5d e9 83 b4 1b cb 48 63 d2 48 c1 e0 04 48 8b 4e 40 48 8d 7e 40 48 8b ac d3 d8 00 00 00 48 89 c3 48 8d 54 05 68 48 8b 46 48 <48> 3b 38 0f 85 b3 3b 00 00 48 3b 79 08 0f 85 a9 3b 00 00 48 89 41
[  604.814332] RSP: 0018:ffffcfe54e3d7578 EFLAGS: 00010256
[  604.814336] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff8cf09eced300
[  604.814339] RDX: 0000000000000068 RSI: ffff8cf1d4c1fc00 RDI: ffff8cf1d4c1fc40
[  604.814341] RBP: 0000000000000000 R08: ffff8cf09eced300 R09: 0000000000000000
[  604.814344] R10: 0000000000000000 R11: 0000000000000016 R12: ffff8cf1d4c1fc00
[  604.814346] R13: 0000000000000400 R14: ffff8cf096289c00 R15: ffff8cf084c8f688
[  604.814349] FS:  00007f00531b7780(0000) GS:ffff8cf4217a0000(0000) knlGS:0000000000000000
[  604.814352] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  604.814355] CR2: 0000000000000000 CR3: 000000018e3df000 CR4: 0000000000350ef0
[  604.814358] Call Trace:
[  604.814362]  <TASK>
[  604.814368]  ttm_bo_swapout_cb+0x24c/0x280 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.814380]  ttm_lru_walk_for_evict+0xac/0x1d0 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.814394]  ttm_bo_swapout+0x5b/0x80 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.814405]  ttm_global_swapout+0x63/0x100 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.814415]  ttm_tt_populate+0x82/0x130 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.814424]  ttm_bo_populate+0x37/0xa0 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.814433]  ttm_bo_handle_move_mem+0x157/0x170 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.814443]  ttm_bo_validate+0xd9/0x180 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.814453]  ttm_bo_init_reserved+0xa0/0x1b0 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.814461]  ? srso_return_thunk+0x5/0x5f
[  604.814469]  amdgpu_bo_create+0x1f5/0x500 [amdgpu 361516226706227f4403914dbfdd3f90996136ca]
[  604.814855]  ? __pfx_amdgpu_bo_user_destroy+0x10/0x10 [amdgpu 361516226706227f4403914dbfdd3f90996136ca]
[  604.815182]  amdgpu_bo_create_user+0x3d/0x70 [amdgpu 361516226706227f4403914dbfdd3f90996136ca]
[  604.815504]  amdgpu_gem_create_ioctl+0x16c/0x3b0 [amdgpu 361516226706227f4403914dbfdd3f90996136ca]
[  604.815830]  ? __pfx_amdgpu_bo_user_destroy+0x10/0x10 [amdgpu 361516226706227f4403914dbfdd3f90996136ca]
[  604.816155]  ? __pfx_amdgpu_gem_create_ioctl+0x10/0x10 [amdgpu 361516226706227f4403914dbfdd3f90996136ca]
[  604.816478]  drm_ioctl_kernel+0xae/0x100
[  604.816486]  drm_ioctl+0x283/0x510
[  604.816491]  ? __pfx_amdgpu_gem_create_ioctl+0x10/0x10 [amdgpu 361516226706227f4403914dbfdd3f90996136ca]
[  604.816819]  amdgpu_drm_ioctl+0x4a/0x80 [amdgpu 361516226706227f4403914dbfdd3f90996136ca]
[  604.817135]  __x64_sys_ioctl+0x96/0xe0
[  604.817142]  do_syscall_64+0x11b/0x7e0
[  604.817148]  ? srso_return_thunk+0x5/0x5f
[  604.817152]  ? srso_return_thunk+0x5/0x5f
[  604.817156]  ? walk_system_ram_range+0xb0/0x110
[  604.817161]  ? srso_return_thunk+0x5/0x5f
[  604.817165]  ? __pte_offset_map+0x1b/0xb0
[  604.817170]  ? srso_return_thunk+0x5/0x5f
[  604.817174]  ? pte_offset_map_lock+0x87/0xf0
[  604.817179]  ? srso_return_thunk+0x5/0x5f
[  604.817183]  ? insert_pfn+0x9f/0x1f0
[  604.817188]  ? srso_return_thunk+0x5/0x5f
[  604.817192]  ? vmf_insert_pfn_prot+0x97/0x190
[  604.817197]  ? srso_return_thunk+0x5/0x5f
[  604.817201]  ? ttm_bo_vm_fault_reserved+0x1a6/0x3f0 [ttm a469cf7fcb6737fdcf3fb5cdbcc8b1ca41f3e302]
[  604.817213]  ? srso_return_thunk+0x5/0x5f
[  604.817217]  ? amdgpu_gem_fault+0xe2/0x100 [amdgpu 361516226706227f4403914dbfdd3f90996136ca]
[  604.817542]  ? srso_return_thunk+0x5/0x5f
[  604.817546]  ? __do_fault+0x33/0x180
[  604.817550]  ? srso_return_thunk+0x5/0x5f
[  604.817554]  ? do_fault+0x178/0x610
[  604.817559]  ? srso_return_thunk+0x5/0x5f
[  604.817562]  ? __handle_mm_fault+0x9be/0x1120
[  604.817567]  ? srso_return_thunk+0x5/0x5f
[  604.817574]  ? srso_return_thunk+0x5/0x5f
[  604.817578]  ? count_memcg_events+0xc4/0x160
[  604.817583]  ? srso_return_thunk+0x5/0x5f
[  604.817587]  ? handle_mm_fault+0x1d7/0x2e0
[  604.817593]  ? srso_return_thunk+0x5/0x5f
[  604.817596]  ? do_user_addr_fault+0x173/0x660
[  604.817602]  ? srso_return_thunk+0x5/0x5f
[  604.817607]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
[  604.817612] RIP: 0033:0x7f00532cef4d
[  604.817617] Code: 04 25 28 00 00 00 48 89 45 c8 31 c0 48 8d 45 10 c7 45 b0 10 00 00 00 48 89 45 b8 48 8d 45 d0 48 89 45 c0 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1a 48 8b 45 c8 64 48 2b 04 25 28 00 00 00
[  604.817620] RSP: 002b:00007ffd69ab0650 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[  604.817624] RAX: ffffffffffffffda RBX: 00007ffd69ab07d0 RCX: 00007f00532cef4d
[  604.817627] RDX: 00007ffd69ab0700 RSI: 00000000c0206440 RDI: 0000000000000005
[  604.817629] RBP: 00007ffd69ab06a0 R08: 00007f00533a0ac0 R09: 0000000000000000
[  604.817632] R10: 00007ffd69ab07c0 R11: 0000000000000246 R12: 00007ffd69ab0700
[  604.817634] R13: 00000000c0206440 R14: 0000000000000005 R15: 0000000000000243
[  604.817642]  </TASK>

Cc: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Christian König <christian.koenig@amd.com>
Fixes: c06da4b3573a ("drm/ttm: Tidy usage of local variables a little bit")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Signed-off-by: Tvrtko Ursulin <tursulin@ursulin.net>
Link: https://lore.kernel.org/r/20260304-ttm_bo_res_uaf-v1-1-43f20125b67f@igalia.com
drivers/gpu/drm/ttm/ttm_bo.c patch | blob | blame | history

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index acb9197db8798659da178186115c2912b84f64e6..0765d69423d2f4028bf2effd21af53e117ee7a29 100644 (file)
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -1107,8 +1107,7 @@ struct ttm_bo_swapout_walk {
 static s64
 ttm_bo_swapout_cb(struct ttm_lru_walk *walk, struct ttm_buffer_object *bo)
 {
-       struct ttm_resource *res = bo->resource;
-       struct ttm_place place = { .mem_type = res->mem_type };
+       struct ttm_place place = { .mem_type = bo->resource->mem_type };
        struct ttm_bo_swapout_walk *swapout_walk =
                container_of(walk, typeof(*swapout_walk), walk);
        struct ttm_operation_ctx *ctx = walk->arg.ctx;
@@ -1148,7 +1147,7 @@ ttm_bo_swapout_cb(struct ttm_lru_walk *walk, struct ttm_buffer_object *bo)
        /*
         * Move to system cached
         */
-       if (res->mem_type != TTM_PL_SYSTEM) {
+       if (bo->resource->mem_type != TTM_PL_SYSTEM) {
                struct ttm_resource *evict_mem;
                struct ttm_place hop;
 
@@ -1180,15 +1179,15 @@ ttm_bo_swapout_cb(struct ttm_lru_walk *walk, struct ttm_buffer_object *bo)
 
        if (ttm_tt_is_populated(tt)) {
                spin_lock(&bdev->lru_lock);
-               ttm_resource_del_bulk_move(res, bo);
+               ttm_resource_del_bulk_move(bo->resource, bo);
                spin_unlock(&bdev->lru_lock);
 
                ret = ttm_tt_swapout(bdev, tt, swapout_walk->gfp_flags);
 
                spin_lock(&bdev->lru_lock);
                if (ret)
-                       ttm_resource_add_bulk_move(res, bo);
-               ttm_resource_move_to_lru_tail(res);
+                       ttm_resource_add_bulk_move(bo->resource, bo);
+               ttm_resource_move_to_lru_tail(bo->resource);
                spin_unlock(&bdev->lru_lock);
        }
 
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