Hello,
syzbot found the following issue on:
HEAD commit: 5ee8dbf54602 Merge tag 'fsverity-for-linus' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=143e4a02580000 kernel config: https://syzkaller.appspot.com/x/.config?x=2a019678b1a3a692 dashboard link: https://syzkaller.appspot.com/bug?extid=7f4987d0afb97dd090cb compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/8f3ca4731c70/disk-5ee8dbf5.raw.... vmlinux: https://storage.googleapis.com/syzbot-assets/9e6d67fcdf59/vmlinux-5ee8dbf5.x... kernel image: https://storage.googleapis.com/syzbot-assets/dd6699ad586c/bzImage-5ee8dbf5.x...
IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+7f4987d0afb97dd090cb@syzkaller.appspotmail.com
================================================================== BUG: KASAN: slab-use-after-free in __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline] BUG: KASAN: slab-use-after-free in _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:162 Read of size 1 at addr ffff888034d9c068 by task syz.6.794/10028
CPU: 1 UID: 0 PID: 10028 Comm: syz.6.794 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: <TASK> dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 __kasan_check_byte+0x2a/0x40 mm/kasan/common.c:574 kasan_check_byte include/linux/kasan.h:402 [inline] lock_acquire+0x79/0x2e0 kernel/locking/lockdep.c:5842 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline] _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:162 rt_mutex_slowunlock+0xbf/0x8b0 kernel/locking/rtmutex.c:1417 spin_unlock include/linux/spinlock_rt.h:109 [inline] class_spinlock_destructor include/linux/spinlock.h:586 [inline] dma_buf_fd+0x189/0x370 drivers/dma-buf/dma-buf.c:796 vb2_core_expbuf+0x37e/0x620 drivers/media/common/videobuf2/videobuf2-core.c:2471 __video_do_ioctl+0x88c/0xc50 drivers/media/v4l2-core/v4l2-ioctl.c:3132 video_usercopy+0x876/0x14b0 drivers/media/v4l2-core/v4l2-ioctl.c:3474 v4l2_ioctl+0x190/0x1e0 drivers/media/v4l2-core/v4l2-dev.c:366 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa4633cc799 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fa46161e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fa463645fa0 RCX: 00007fa4633cc799 RDX: 0000200000000040 RSI: 00000000c0405610 RDI: 0000000000000004 RBP: 00007fa463462bd9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa463646038 R14: 00007fa463645fa0 R15: 00007ffe4429d3d8 </TASK>
Allocated by task 10028: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __do_kmalloc_node mm/slub.c:5238 [inline] __kmalloc_noprof+0x3e7/0x7b0 mm/slub.c:5250 kmalloc_noprof include/linux/slab.h:954 [inline] kzalloc_noprof include/linux/slab.h:1188 [inline] dma_buf_export+0x3ba/0xb10 drivers/dma-buf/dma-buf.c:739 vb2_vmalloc_get_dmabuf+0x10e/0x210 drivers/media/common/videobuf2/videobuf2-vmalloc.c:352 vb2_core_expbuf+0x314/0x620 drivers/media/common/videobuf2/videobuf2-core.c:2461 __video_do_ioctl+0x88c/0xc50 drivers/media/v4l2-core/v4l2-ioctl.c:3132 video_usercopy+0x876/0x14b0 drivers/media/v4l2-core/v4l2-ioctl.c:3474 v4l2_ioctl+0x190/0x1e0 drivers/media/v4l2-core/v4l2-dev.c:366 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xff/0x170 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 10031: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2692 [inline] slab_free mm/slub.c:6143 [inline] kfree+0x1c1/0x6c0 mm/slub.c:6461 __dentry_kill+0x211/0x5e0 fs/dcache.c:675 finish_dput+0xc9/0x480 fs/dcache.c:879 __fput+0x6a3/0xa90 fs/file_table.c:477 task_work_run+0x1d9/0x270 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:67 [inline] exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline] do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff888034d9c000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 104 bytes inside of freed 1024-byte region [ffff888034d9c000, ffff888034d9c400)
The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x34d98 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x80000000000040(head|node=0|zone=1) page_type: f5(slab) raw: 0080000000000040 ffff88813fe1cdc0 dead000000000100 dead000000000122 raw: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000 head: 0080000000000040 ffff88813fe1cdc0 dead000000000100 dead000000000122 head: 0000000000000000 0000000800100010 00000000f5000000 0000000000000000 head: 0080000000000003 ffffea0000d36601 00000000ffffffff 00000000ffffffff head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000008 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6221, tgid 6216 (syz.3.71), ts 173025510293, free_ts 172769017733 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889 prep_new_page mm/page_alloc.c:1897 [inline] get_page_from_freelist+0x28bb/0x2950 mm/page_alloc.c:3962 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250 alloc_slab_page mm/slub.c:3269 [inline] allocate_slab+0x77/0x660 mm/slub.c:3458 new_slab mm/slub.c:3516 [inline] refill_objects+0x334/0x3c0 mm/slub.c:7153 refill_sheaf mm/slub.c:2818 [inline] __pcs_replace_empty_main+0x328/0x5f0 mm/slub.c:4592 alloc_from_pcs mm/slub.c:4695 [inline] slab_alloc_node mm/slub.c:4829 [inline] __kmalloc_cache_noprof+0x44e/0x690 mm/slub.c:5353 kmalloc_noprof include/linux/slab.h:950 [inline] kzalloc_noprof include/linux/slab.h:1188 [inline] snd_seq_oss_open+0x125/0xfc0 sound/core/seq/oss/seq_oss_init.c:171 odev_open+0x67/0xd0 sound/core/seq/oss/seq_oss.c:128 chrdev_open+0x4d0/0x5f0 fs/char_dev.c:411 do_dentry_open+0x83d/0x13e0 fs/open.c:949 vfs_open+0x3b/0x350 fs/open.c:1081 do_open fs/namei.c:4671 [inline] path_openat+0x2e43/0x38a0 fs/namei.c:4830 do_file_open+0x23e/0x4a0 fs/namei.c:4859 do_sys_openat2+0x113/0x200 fs/open.c:1366 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1383 page last free pid 6219 tgid 6219 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1433 [inline] __free_frozen_pages+0xfe3/0x1170 mm/page_alloc.c:2978 __slab_free+0x24f/0x2a0 mm/slub.c:5551 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4515 [inline] slab_alloc_node mm/slub.c:4844 [inline] kmem_cache_alloc_noprof+0x33b/0x680 mm/slub.c:4851 vm_area_dup+0x2b/0x670 mm/vma_init.c:123 __split_vma+0x1e4/0xa30 mm/vma.c:513 split_vma mm/vma.c:596 [inline] vma_modify+0x94b/0x1f00 mm/vma.c:1672 vma_modify_flags+0x24b/0x330 mm/vma.c:1700 mprotect_fixup+0x47a/0xa80 mm/mprotect.c:756 do_mprotect_pkey+0x8ab/0xcd0 mm/mprotect.c:930 __do_sys_mprotect mm/mprotect.c:951 [inline] __se_sys_mprotect mm/mprotect.c:948 [inline] __x64_sys_mprotect+0x80/0x90 mm/mprotect.c:948 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f
Memory state around the buggy address: ffff888034d9bf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888034d9bf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888034d9c000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff888034d9c080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888034d9c100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================
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