Reviewed-by: Lyude Paul <[email protected]>
Will push to drm-misc-fixes in a moment
On Wed, 2026-09-16 at 18:31 +0800, Peiyang He wrote:
> On failure, nouveau_cli_init() calls nouveau_cli_fini() to tear
> the client down. Then, nouveau_drm_open() also enters into its
> cleanup path and calls nouveau_cli_fini() AGAIN. nouveau_cli_fini()
> calls nouveau_vmm_fini():
>
> void
> nouveau_vmm_fini(struct nouveau_vmm *vmm)
> {
> nouveau_svmm_fini(&vmm->svmm);
> nvif_vmm_dtor(&vmm->vmm);
> vmm->cli = NULL;
> }
>
> Inside nvif_vmm_dtor(), vmm->page is freed unconditionally:
>
> void
> nvif_vmm_dtor(struct nvif_vmm *vmm)
> {
> kfree(vmm->page);
> nvif_object_dtor(&vmm->object);
> }
>
> vmm->page is never cleared after being freed, so the second call of
> nvif_vmm_dtor() will cause a double-free.
>
> Found by fuzzing the nouveau driver with a modified Syzkaller:
>
> BUG: KASAN: double-free in nvif_vmm_dtor+0x31/0x50
> drivers/gpu/drm/nouveau/nvif/vmm.c:194
> Free of addr ffff888010fcdc30 by task syz.0.173/2567
>
> CPU: 1 UID: 0 PID: 2567 Comm: syz.0.173 Not tainted 7.2.0
> #24 PREEMPT(lazy)
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS
> 1.16.3-debian-1.16.3-2 04/01/2014
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:94 [inline]
> dump_stack_lvl+0x95/0xe0 lib/dump_stack.c:120
> print_address_description mm/kasan/report.c:378 [inline]
> print_report+0xcb/0x5a0 mm/kasan/report.c:482
> kasan_report_invalid_free+0xaa/0xd0 mm/kasan/report.c:557
> check_slab_allocation+0xe4/0x110 mm/kasan/common.c:235
> kasan_slab_pre_free include/linux/kasan.h:199 [inline]
> slab_free_hook mm/slub.c:2622 [inline]
> slab_free mm/slub.c:6377 [inline]
> kfree+0x192/0x590 mm/slub.c:6692
> nvif_vmm_dtor+0x31/0x50
> drivers/gpu/drm/nouveau/nvif/vmm.c:194
> nouveau_vmm_fini+0x16/0x50
> drivers/gpu/drm/nouveau/nouveau_vmm.c:127
> nouveau_cli_fini+0x10e/0x210
> drivers/gpu/drm/nouveau/nouveau_drm.c:225
> nouveau_drm_open+0x24e/0x740
> drivers/gpu/drm/nouveau/nouveau_drm.c:1255
> drm_file_alloc+0x5f2/0xad0 drivers/gpu/drm/drm_file.c:176
> drm_open_helper+0x1d7/0x4a0 drivers/gpu/drm/drm_file.c:335
> drm_open+0x190/0x3d0 drivers/gpu/drm/drm_file.c:388
> drm_stub_open+0x1f2/0x460 drivers/gpu/drm/drm_drv.c:1211
> chrdev_open+0x21c/0x660 fs/char_dev.c:411
> do_dentry_open+0x59d/0x12b0 fs/open.c:947
> vfs_open+0x82/0x390 fs/open.c:1052
> do_open fs/namei.c:4700 [inline]
> path_openat+0x2345/0x3420 fs/namei.c:4863
> do_file_open+0x207/0x460 fs/namei.c:4892
> do_sys_openat2+0xd1/0x1d0 fs/open.c:1368
> do_sys_open fs/open.c:1374 [inline]
> __do_sys_openat fs/open.c:1390 [inline]
> __se_sys_openat fs/open.c:1385 [inline]
> __x64_sys_openat+0x144/0x200 fs/open.c:1385
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0x115/0x690 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fc6d687594d
> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48
> 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f
> 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01
> 48
> RSP: 002b:00007fc6d5295008 EFLAGS: 00000246 ORIG_RAX:
> 0000000000000101
> RAX: ffffffffffffffda RBX: 00007fc6d6b06180 RCX:
> 00007fc6d687594d
> RDX: 0000000000022501 RSI: 0000200000000000 RDI:
> ffffffffffffff9c
> RBP: 00007fc6d691c303 R08: 0000000000000000 R09:
> 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12:
> 0000000000000000
> R13: 00007fc6d6b06218 R14: 00007fc6d6b06180 R15:
> 00007ffd9451d760
> </TASK>
>
> Allocated by task 2567 on cpu 1 at 163.593900s:
> kasan_save_stack+0x24/0x50 mm/kasan/common.c:57
> kasan_save_track+0x17/0x60 mm/kasan/common.c:78
> poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
> __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
> kasan_kmalloc include/linux/kasan.h:263 [inline]
> __do_kmalloc_node mm/slub.c:5334 [inline]
> __kmalloc_noprof+0x304/0x7c0 mm/slub.c:5359
> _kmalloc_noprof include/linux/slab.h:992 [inline]
> nvif_vmm_ctor+0x3c0/0x7e0
> drivers/gpu/drm/nouveau/nvif/vmm.c:237
> nouveau_vmm_init+0x40/0x90
> drivers/gpu/drm/nouveau/nouveau_vmm.c:134
> nouveau_cli_init+0x7b9/0xe10
> drivers/gpu/drm/nouveau/nouveau_drm.c:293
> nouveau_drm_open+0x236/0x740
> drivers/gpu/drm/nouveau/nouveau_drm.c:1243
> drm_file_alloc+0x5f2/0xad0 drivers/gpu/drm/drm_file.c:176
> drm_open_helper+0x1d7/0x4a0 drivers/gpu/drm/drm_file.c:335
> drm_open+0x190/0x3d0 drivers/gpu/drm/drm_file.c:388
> drm_stub_open+0x1f2/0x460 drivers/gpu/drm/drm_drv.c:1211
> chrdev_open+0x21c/0x660 fs/char_dev.c:411
> do_dentry_open+0x59d/0x12b0 fs/open.c:947
> vfs_open+0x82/0x390 fs/open.c:1052
> do_open fs/namei.c:4700 [inline]
> path_openat+0x2345/0x3420 fs/namei.c:4863
> do_file_open+0x207/0x460 fs/namei.c:4892
> do_sys_openat2+0xd1/0x1d0 fs/open.c:1368
> do_sys_open fs/open.c:1374 [inline]
> __do_sys_openat fs/open.c:1390 [inline]
> __se_sys_openat fs/open.c:1385 [inline]
> __x64_sys_openat+0x144/0x200 fs/open.c:1385
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0x115/0x690 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> Freed by task 2567 on cpu 1 at 163.601355s:
> kasan_save_stack+0x24/0x50 mm/kasan/common.c:57
> kasan_save_track+0x17/0x60 mm/kasan/common.c:78
> kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:584
> poison_slab_object mm/kasan/common.c:253 [inline]
> __kasan_slab_free+0x61/0x80 mm/kasan/common.c:285
> kasan_slab_free include/linux/kasan.h:235 [inline]
> slab_free_hook mm/slub.c:2677 [inline]
> slab_free mm/slub.c:6377 [inline]
> kfree+0x383/0x590 mm/slub.c:6692
> nvif_vmm_dtor+0x31/0x50
> drivers/gpu/drm/nouveau/nvif/vmm.c:194
> nouveau_vmm_fini+0x16/0x50
> drivers/gpu/drm/nouveau/nouveau_vmm.c:127
> nouveau_cli_fini+0x10e/0x210
> drivers/gpu/drm/nouveau/nouveau_drm.c:225
> nouveau_cli_init+0x593/0xe10
> drivers/gpu/drm/nouveau/nouveau_drm.c:324
> nouveau_drm_open+0x236/0x740
> drivers/gpu/drm/nouveau/nouveau_drm.c:1243
> drm_file_alloc+0x5f2/0xad0 drivers/gpu/drm/drm_file.c:176
> drm_open_helper+0x1d7/0x4a0 drivers/gpu/drm/drm_file.c:335
> drm_open+0x190/0x3d0 drivers/gpu/drm/drm_file.c:388
> drm_stub_open+0x1f2/0x460 drivers/gpu/drm/drm_drv.c:1211
> chrdev_open+0x21c/0x660 fs/char_dev.c:411
> do_dentry_open+0x59d/0x12b0 fs/open.c:947
> vfs_open+0x82/0x390 fs/open.c:1052
> do_open fs/namei.c:4700 [inline]
> path_openat+0x2345/0x3420 fs/namei.c:4863
> do_file_open+0x207/0x460 fs/namei.c:4892
> do_sys_openat2+0xd1/0x1d0 fs/open.c:1368
> do_sys_open fs/open.c:1374 [inline]
> __do_sys_openat fs/open.c:1390 [inline]
> __se_sys_openat fs/open.c:1385 [inline]
> __x64_sys_openat+0x144/0x200 fs/open.c:1385
> do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> do_syscall_64+0x115/0x690 arch/x86/entry/syscall_64.c:94
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
>
> The buggy address belongs to the object at ffff888010fcdc30
> which belongs to the cache kmalloc-16 of size 16
> The buggy address is located 0 bytes inside of
> 16-byte region [ffff888010fcdc30, ffff888010fcdc40)
>
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000
> index:0x0 pfn:0x10fcd
> flags: 0x100000000000000(node=0|zone=1)
> page_type: f5(slab)
> raw: 0100000000000000 ffff88800d441640 dead000000000100
> dead000000000122
> raw: 0000000000000000 0000000000550055 00000000f5000000
> 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff888010fcdb00: fc fc 00 04 fc fc fc fc fa fb fc fc fc fc
> fa fb
> ffff888010fcdb80: fc fc fc fc fa fb fc fc fc fc 00 07 fc fc
> fc fc
> >ffff888010fcdc00: fa fb fc fc fc fc fa fb fc fc fc fc fa fb
> fc fc
>
> ^
> ffff888010fcdc80: fc fc fa fb fc fc fc fc 00 04 fc fc fc fc
> fa fb
> ffff888010fcdd00: fc fc fc fc 00 00 fc fc fc fc fa fb fc fc
> fc fc
>
> Fix by removing the redundant teardown in nouveau_drm_open(),
> since nouveau_cli_init() already does the cleanup work.
> Also clear vmm->page after its freeing.
>
> Cc: [email protected]
> Fixes: 20d8a88e557a ("drm/nouveau: tidy up the client init/fini
> interfaces")
> Signed-off-by: Peiyang He <[email protected]>
> Assisted-by: LLM
> ---
> drivers/gpu/drm/nouveau/nouveau_drm.c | 4 +---
> drivers/gpu/drm/nouveau/nvif/vmm.c | 1 +
> 2 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c
> b/drivers/gpu/drm/nouveau/nouveau_drm.c
> index e16f59b00f6f..c465d59ef0a6 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_drm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
> @@ -1251,10 +1251,8 @@ nouveau_drm_open(struct drm_device *dev,
> struct drm_file *fpriv)
> mutex_unlock(&drm->clients_lock);
>
> done:
> - if (ret && cli) {
> - nouveau_cli_fini(cli);
> + if (ret && cli)
> kfree(cli);
> - }
>
> pm_runtime_mark_last_busy(dev->dev);
> pm_runtime_put_autosuspend(dev->dev);
> diff --git a/drivers/gpu/drm/nouveau/nvif/vmm.c
> b/drivers/gpu/drm/nouveau/nvif/vmm.c
> index 65c3e883b119..579af70766f2 100644
> --- a/drivers/gpu/drm/nouveau/nvif/vmm.c
> +++ b/drivers/gpu/drm/nouveau/nvif/vmm.c
> @@ -192,6 +192,7 @@ void
> nvif_vmm_dtor(struct nvif_vmm *vmm)
> {
> kfree(vmm->page);
> + vmm->page = NULL;
> nvif_object_dtor(&vmm->object);
> }
>
