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* [PATCH] drm/nouveau: fix double-free in nvif_vmm_dtor
@ 2026-09-16 10:31 Peiyang He
  2026-09-17 19:21 ` lyude
  0 siblings, 1 reply; 2+ messages in thread
From: Peiyang He @ 2026-09-16 10:31 UTC (permalink / raw)
  To: lyude, dakr, dri-devel, nouveau
  Cc: linux-kernel, stable, bskeggs, maarten.lankhorst, mripard,
	tzimmermann, Peiyang He

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: stable@vger.kernel.org
Fixes: 20d8a88e557a ("drm/nouveau: tidy up the client init/fini interfaces")
Signed-off-by: Peiyang He <peiyang_he@smail.nju.edu.cn>
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);
 }
 
-- 
2.43.0

^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-09-17 19:21 UTC | newest]

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2026-09-16 10:31 [PATCH] drm/nouveau: fix double-free in nvif_vmm_dtor Peiyang He
2026-09-17 19:21 ` lyude

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