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KASAN: use-after-free Read in path_put

Status: premoderation: reported on 2026/03/03 17:44
Reported-by: syzbot+6ba9888b1999e34d6cde@syzkaller.appspotmail.com
First crash: 36d, last: 30d

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in fast_dput+0x1e9/0x290 fs/dcache.c:750
Read of size 4 at addr ffff88812da4b880 by task syz-executor/556

CPU: 1 PID: 556 Comm: syz-executor Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 fast_dput+0x1e9/0x290 fs/dcache.c:750
 dput+0x21/0x80 fs/dcache.c:870
 path_put+0x39/0x60 fs/namei.c:499
 dentry_release+0x4f/0xa0 fs/incfs/vfs.c:1591
 __dentry_kill+0x4b5/0x650 fs/dcache.c:588
 shrink_dentry_list+0x38e/0x500 fs/dcache.c:1146
 shrink_dcache_parent+0xa9/0x270 fs/dcache.c:-1
 do_one_tree+0x27/0x150 fs/dcache.c:1627
 shrink_dcache_for_umount+0x6a/0x110 fs/dcache.c:1644
 generic_shutdown_super+0x66/0x320 fs/super.c:447
 kill_anon_super+0x3a/0x70 fs/super.c:1131
 incfs_kill_sb+0x4c/0x210 fs/incfs/vfs.c:1965
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x45b/0x510 fs/namespace.c:1123
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1130
 task_work_run+0x127/0x190 kernel/task_work.c:189
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa90/0x2500 kernel/exit.c:872
 do_group_exit+0x141/0x310 kernel/exit.c:986
 __do_sys_exit_group kernel/exit.c:997 [inline]
 __se_sys_exit_group kernel/exit.c:995 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:995
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fe9b9c49799
Code: Unable to access opcode bytes at RIP 0x7fe9b9c4976f.
RSP: 002b:00007ffeb5dbaec8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fe9b9cdeff0 RCX: 00007fe9b9c49799
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000009 R08: 0000000000000000 R09: 00007fe9b9cdef90
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffeb5dbc180
R13: 00007fe9b9cdef90 R14: 0000555557fd14e8 R15: 00007ffeb5dbd250

Allocated by task 1330:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 __kasan_slab_alloc+0xbd/0xf0 mm/kasan/common.c:463
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x162/0x2d0 mm/slub.c:2965
 __d_alloc+0x2d/0x6a0 fs/dcache.c:1714
 d_alloc+0x4b/0x260 fs/dcache.c:1793
 __lookup_hash+0xcb/0x250 fs/namei.c:1545
 filename_create+0x1d5/0x680 fs/namei.c:3616
 user_path_create fs/namei.c:3673 [inline]
 do_mkdirat+0x5e/0x340 fs/namei.c:3813
 __do_sys_mkdirat fs/namei.c:3831 [inline]
 __se_sys_mkdirat fs/namei.c:3829 [inline]
 __x64_sys_mkdirat+0x7b/0x90 fs/namei.c:3829
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 556:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kmem_cache_free+0x100/0x2d0 mm/slub.c:3224
 __d_free+0x23/0x30 fs/dcache.c:271
 rcu_do_batch+0x4ef/0xab0 kernel/rcu/tree.c:2494
 rcu_core+0x577/0xd80 kernel/rcu/tree.c:2735
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748
 __do_softirq+0x255/0x563 kernel/softirq.c:309

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu kernel/rcu/tree.c:2980 [inline]
 call_rcu+0x11a/0x10b0 kernel/rcu/tree.c:3054
 dentry_free+0xbd/0x150 fs/dcache.c:-1
 __dentry_kill+0x50a/0x650 fs/dcache.c:597
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x42/0x80 fs/dcache.c:883
 do_rmdir+0x24b/0x630 fs/namei.c:3922
 __do_sys_unlinkat fs/namei.c:4084 [inline]
 __se_sys_unlinkat fs/namei.c:4078 [inline]
 __x64_sys_unlinkat+0xc7/0xf0 fs/namei.c:4078
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88812da4b880
 which belongs to the cache dentry of size 208
The buggy address is located 0 bytes inside of
 208-byte region [ffff88812da4b880, ffff88812da4b950)
The buggy address belongs to the page:
page:ffffea0004b692c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12da4b
flags: 0x4000000000000200(slab)
raw: 4000000000000200 dead000000000100 dead000000000122 ffff88810018bb00
raw: 0000000000000000 00000000000f000f 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Reclaimable, gfp_mask 0x112cd0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY|__GFP_RECLAIMABLE), pid 1329, ts 58041348500, free_ts 53503204237
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x223b/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x290/0x620 mm/page_alloc.c:5370
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2a6/0x450 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x1ac/0x2d0 mm/slub.c:2965
 __d_alloc+0x2d/0x6a0 fs/dcache.c:1714
 d_alloc fs/dcache.c:1793 [inline]
 d_alloc_parallel+0xdf/0x1380 fs/dcache.c:2549
 __lookup_slow+0x14c/0x410 fs/namei.c:1633
 lookup_slow+0x57/0x70 fs/namei.c:1665
 walk_component+0x325/0x460 fs/namei.c:1960
 link_path_walk+0x5b2/0xba0 fs/namei.c:-1
 path_openat+0x27c/0x31c0 fs/namei.c:3513
 do_filp_open+0x1e2/0x410 fs/namei.c:3544
 do_sys_openat2+0x19f/0x750 fs/open.c:1219
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5431 [inline]
 __free_pages+0xd8/0x3b0 mm/page_alloc.c:5440
 __free_slab+0xcf/0x190 mm/slub.c:1899
 free_slab mm/slub.c:1914 [inline]
 discard_slab mm/slub.c:1920 [inline]
 unfreeze_partials+0x15f/0x190 mm/slub.c:2415
 put_cpu_partial+0xc1/0x180 mm/slub.c:2451
 __slab_free+0x2c9/0x3a0 mm/slub.c:3100
 do_slab_free mm/slub.c:3196 [inline]
 ___cache_free+0x10e/0x130 mm/slub.c:3215
 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xf0 mm/kasan/common.c:440
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x162/0x2d0 mm/slub.c:2965
 getname_flags+0xb9/0x500 fs/namei.c:141
 getname+0x19/0x20 fs/namei.c:212
 do_sys_openat2+0xde/0x750 fs/open.c:1213

Memory state around the buggy address:
 ffff88812da4b780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88812da4b800: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff88812da4b880: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88812da4b900: fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc
 ffff88812da4b980: fc fc fa fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 0 PID: 556 at fs/dcache.c:766 fast_dput+0x210/0x290 fs/dcache.c:766
Modules linked in:
CPU: 0 PID: 556 Comm: syz-executor Tainted: G    B   W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:fast_dput+0x210/0x290 fs/dcache.c:766
Code: d5 f2 ff e9 46 fe ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c 99 fe ff ff 48 89 df e8 8a d5 f2 ff e9 8c fe ff ff e8 70 54 b8 ff <0f> 0b e9 0b ff ff ff 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c e4 fe ff
RSP: 0018:ffffc90000c178f8 EFLAGS: 00010293
RAX: ffffffff81ac61e0 RBX: ffff88812da4b880 RCX: ffff88811a573b40
RDX: 0000000000000000 RSI: 00000000ffffff80 RDI: 0000000000000001
RBP: ffffc90000c17928 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000182f10 R12: 00000000ffffff80
R13: dffffc0000000000 R14: ffff88812da4b8d8 R15: 1ffff11025b4971b
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe2386f33eb CR3: 000000010d505000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 dput+0x21/0x80 fs/dcache.c:870
 path_put+0x39/0x60 fs/namei.c:499
 dentry_release+0x4f/0xa0 fs/incfs/vfs.c:1591
 __dentry_kill+0x4b5/0x650 fs/dcache.c:588
 shrink_dentry_list+0x38e/0x500 fs/dcache.c:1146
 shrink_dcache_parent+0xa9/0x270 fs/dcache.c:-1
 do_one_tree+0x27/0x150 fs/dcache.c:1627
 shrink_dcache_for_umount+0x6a/0x110 fs/dcache.c:1644
 generic_shutdown_super+0x66/0x320 fs/super.c:447
 kill_anon_super+0x3a/0x70 fs/super.c:1131
 incfs_kill_sb+0x4c/0x210 fs/incfs/vfs.c:1965
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x45b/0x510 fs/namespace.c:1123
 __cleanup_mnt+0x19/0x20 fs/namespace.c:1130
 task_work_run+0x127/0x190 kernel/task_work.c:189
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa90/0x2500 kernel/exit.c:872
 do_group_exit+0x141/0x310 kernel/exit.c:986
 __do_sys_exit_group kernel/exit.c:997 [inline]
 __se_sys_exit_group kernel/exit.c:995 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:995
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fe9b9c49799
Code: Unable to access opcode bytes at RIP 0x7fe9b9c4976f.
RSP: 002b:00007ffeb5dbaec8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fe9b9cdeff0 RCX: 00007fe9b9c49799
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000009 R08: 0000000000000000 R09: 00007fe9b9cdef90
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffeb5dbc180
R13: 00007fe9b9cdef90 R14: 0000555557fd14e8 R15: 00007ffeb5dbd250
---[ end trace 482c30011b364b48 ]---

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/09 07:15 android13-5.10-lts 9a301c292a32 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in path_put
2026/03/08 22:14 android13-5.10-lts 9a301c292a32 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in path_put
2026/03/08 16:23 android13-5.10-lts 9a301c292a32 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in path_put
2026/03/08 10:01 android13-5.10-lts 9a301c292a32 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in path_put
2026/03/07 20:40 android13-5.10-lts 9a301c292a32 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in path_put
2026/03/07 20:39 android13-5.10-lts 9a301c292a32 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in path_put
2026/03/04 10:24 android13-5.10-lts dad37bbb13a8 4180d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in path_put
2026/03/03 17:43 android13-5.10-lts dad37bbb13a8 4180d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in path_put
* Struck through repros no longer work on HEAD.