Re: [PATCH v2] drm/nouveau: don't bump pin count on failed re-pin in nouveau_bo_pin_locked()

From: lyude

Date: Fri Sep 18 2026 - 14:21:34 EST

Reviewed-by: Lyude Paul <lyude@xxxxxxxxxx>

Will push to drm-misc-fixes in just a moment

On Fri, 2026-09-18 at 10:53 +0800, Peiyang He wrote:
> nouveau_bo_pin_locked() checks whether an already pinned BO is in a
> memory domain compatible with a new pin request. When the domains are
> incompatible, it sets -EBUSY but still calls ttm_bo_pin() before
> returning.
>
> Callers treat a failed nouveau_bo_pin() as not having acquired a new
> pin,
> so the extra pin count is never decreased by a matching unpin.
> This triggers the warning in ttm_bo_release():
>
> WARN_ON_ONCE(bo->pin_count);
>
> Found when fuzzing the nouveau driver with a modified Syzkaller:
>
> WARNING: drivers/gpu/drm/ttm/ttm_bo.c:256 at
> ttm_bo_release+0x827/0x9e0 drivers/gpu/drm/ttm/ttm_bo.c:256, CPU#1:
> syz.3.24/2212
> Modules linked in:
> CPU: 1 UID: 0 PID: 2212 Comm: syz.3.24 Not tainted 7.2.0 #24
> PREEMPT(lazy)
> nouveau 0000:01:00.0: gsp:msg fn:103 len:0x40/0x20 res:0x19
> resp:0x19
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
> 1.16.3-debian-1.16.3-2 04/01/2014
> RIP: 0010:ttm_bo_release+0x827/0x9e0
> drivers/gpu/drm/ttm/ttm_bo.c:256
> Code: 02 00 0f 85 51 01 00 00 48 8b 7b 08 e8 d2 20 01 00 e9
> 80 fd ff ff e8 d8 15 c0 fe 90 0f 0b 90 e9 e1 f8 ff ff e8 ca 15 c0 fe
> 90 <0f> 0b 90 e9 a4 f8 ff ff e8 bc 15 c0 fe be 03 00 00 00 4c 89 e7
> e8
> msg: 00000000: 05 00 d0 c1 04 00 f0 f1 01 30 00 00 2d 90 00
> 00 .........0..-...
> RSP: 0018:ffffc9000f5cf710 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff888018e5d2a8 RCX:
> ffffffff82bb1b36
> RDX: ffff888017b68000 RSI: 0000000000000004 RDI:
> ffff888018e5d2a8
> msg: 00000010: 19 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 00 ................
> RBP: ffff88801261c720 R08: 0000000000000001 R09:
> ffffed10031cba55
> R10: ffff888018e5d2ab R11: 00000000000000f3 R12:
> ffff888018e5d290
> R13: ffff888018e5d2d4 R14: ffff88801b219c18 R15:
> dffffc0000000000
> FS: 0000000000000000(0000) GS:ffff8880e0f6f000(0000)
> knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001b31223ffc CR3: 0000000028e00005 CR4:
> 0000000000770ef0
> PKRU: 80000000
> Call Trace:
> <TASK>
> kref_put include/linux/kref.h:65 [inline]
> ttm_bo_put drivers/gpu/drm/ttm/ttm_bo.c:325 [inline]
> ttm_bo_fini+0x55/0x80 drivers/gpu/drm/ttm/ttm_bo.c:330
> nouveau_gem_object_del+0xb2/0x1b0
> drivers/gpu/drm/nouveau/nouveau_gem.c:90
> drm_gem_object_free+0x5f/0x90 drivers/gpu/drm/drm_gem.c:1165
> kref_put include/linux/kref.h:65 [inline]
> __drm_gem_object_put include/drm/drm_gem.h:562 [inline]
> drm_gem_object_put include/drm/drm_gem.h:575 [inline]
> nouveau_abi16_chan_fini.constprop.0+0x44f/0x5a0
> drivers/gpu/drm/nouveau/nouveau_abi16.c:195
> nouveau 0000:01:00.0: syz.2.23[2209]: Unknown handle
> 0x00000000
> nouveau_abi16_fini+0x1d0/0x340
> drivers/gpu/drm/nouveau/nouveau_abi16.c:225
> nouveau_drm_postclose+0x18b/0x3e0
> drivers/gpu/drm/nouveau/nouveau_drm.c:1284
> nouveau 0000:01:00.0: syz.2.23[2209]: validate_init
> drm_file_free.part.0+0x6d6/0xb60
> drivers/gpu/drm/drm_file.c:267
> drm_file_free drivers/gpu/drm/drm_file.c:237 [inline]
> drm_close_helper.isra.0+0x11a/0x160
> drivers/gpu/drm/drm_file.c:290
> drm_release+0x1ab/0x330 drivers/gpu/drm/drm_file.c:438
> __fput+0x39c/0xa60 fs/file_table.c:512
> nouveau 0000:01:00.0: syz.2.23[2209]: validate: -2
> task_work_run+0x15a/0x230 kernel/task_work.c:233
> exit_task_work include/linux/task_work.h:40 [inline]
> do_exit+0x82b/0x25a0 kernel/exit.c:1009
> do_group_exit+0xc2/0x280 kernel/exit.c:1152
> get_signal+0x1d6e/0x1f30 kernel/signal.c:3046
> arch_do_signal_or_restart+0x7d/0x6e0
> arch/x86/kernel/signal.c:337
> __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
> exit_to_user_mode_loop+0xdf/0x440 kernel/entry/common.c:101
> __exit_to_user_mode_prepare include/linux/irq-entry-
> common.h:207 [inline]
> syscall_exit_to_user_mode_prepare include/linux/irq-entry-
> common.h:230 [inline]
> syscall_exit_to_user_mode include/linux/entry-common.h:318
> [inline]
> do_syscall_64+0x4f8/0x690 arch/x86/entry/syscall_64.c:100
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f12bac8594d
> Code: Unable to access opcode bytes at 0x7f12bac85923.
> RSP: 002b:00007f12b96e70d8 EFLAGS: 00000246 ORIG_RAX:
> 00000000000000ca
> RAX: 0000000000000001 RBX: 00007f12baf15fa8 RCX:
> 00007f12bac8594d
> RDX: 00000000000f4240 RSI: 0000000000000081 RDI:
> 00007f12baf15fac
> RBP: 00007f12baf15fa0 R08: 00007f12baee8000 R09:
> 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12:
> 0000000000000000
> R13: 00007f12baf16038 R14: 0000000000000006 R15:
> 00007ffe2ed394b0
> </TASK>
> irq event stamp: 47867
> hardirqs last enabled at (47883): [<ffffffff815cafc6>]
> __up_console_sem+0x66/0x70 kernel/printk/printk.c:347
> hardirqs last disabled at (47892): [<ffffffff815cafab>]
> __up_console_sem+0x4b/0x70 kernel/printk/printk.c:345
> softirqs last enabled at (47880): [<ffffffff81434277>]
> __do_softirq kernel/softirq.c:656 [inline]
> softirqs last enabled at (47880): [<ffffffff81434277>]
> invoke_softirq kernel/softirq.c:496 [inline]
> softirqs last enabled at (47880): [<ffffffff81434277>]
> __irq_exit_rcu+0x137/0x1c0 kernel/softirq.c:735
> softirqs last disabled at (47875): [<ffffffff81434277>]
> __do_softirq kernel/softirq.c:656 [inline]
> softirqs last disabled at (47875): [<ffffffff81434277>]
> invoke_softirq kernel/softirq.c:496 [inline]
> softirqs last disabled at (47875): [<ffffffff81434277>]
> __irq_exit_rcu+0x137/0x1c0 kernel/softirq.c:735
>
> Fix by calling ttm_bo_pin() only when the existing placement is
> compatible
> with the new pin request. This matches the correct behavior in other
> DRM
> drivers such as amdgpu_bo_pin() in amdgpu.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: ad76b3f7c7a0 ("drm/nouveau: teach nouveau_bo_pin() how to
> force a contig vram allocation")
> Signed-off-by: Peiyang He <peiyang_he@xxxxxxxxxxxxxxxx>
> Assisted-by: LLM
> ---
> Changes in v2:
> - replace goto with else branch (suggested by Lyude Paul)
> - fix Assisted-by tag
>
> drivers/gpu/drm/nouveau/nouveau_bo.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c
> b/drivers/gpu/drm/nouveau/nouveau_bo.c
> index 0e8de6d4b36f..6dcb92575eb4 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> @@ -578,8 +578,9 @@ int nouveau_bo_pin_locked(struct nouveau_bo
> *nvbo, uint32_t domain, bool contig)
> "0x%08x vs 0x%08x\n", bo,
> bo->resource->mem_type, domain);
> ret = -EBUSY;
> + } else {
> + ttm_bo_pin(&nvbo->bo);
> }
> - ttm_bo_pin(&nvbo->bo);
> goto out;
> }
>
>
> base-commit: df2908090cda368b01ff43709f51890076c56157