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KASAN: use-after-free Read in fast_dput (3)

Status: premoderation: reported on 2025/08/26 09:24
Reported-by: syzbot+6d1075923ca21f70fba5@syzkaller.appspotmail.com
First crash: 110d, last: 2d09h
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: use-after-free Read in fast_dput 19 3 5d07h 50d 0/2 premoderation: reported on 2025/10/25 11:04
android-5-15 KASAN: use-after-free Read in fast_dput 19 1 321d 321d 0/2 auto-obsoleted due to no activity on 2025/04/27 04:39
android-5-10 KASAN: use-after-free Read in fast_dput 19 14 328d 517d 0/2 auto-obsoleted due to no activity on 2025/04/20 07:57
android-5-15 KASAN: use-after-free Read in fast_dput (2) 19 21 4h09m 55d 0/2 premoderation: reported on 2025/10/20 04:48
android-5-10 KASAN: use-after-free Read in fast_dput (2) 19 1 223d 223d 0/2 auto-obsoleted due to no activity on 2025/08/03 11:21

Sample crash report:
RBP: 0000000000000009 R08: 00007fff31b7de97 R09: 00007fff31b813b0
R10: 0000000000000009 R11: 0000000000000246 R12: 00007fff31b813b0
R13: 00007fc5bd3e2d7d R14: 000055556886f4a8 R15: 00007fff31b82480
---[ end trace cd7fff5fb2ae7116 ]---
==================================================================
BUG: KASAN: use-after-free in fast_dput+0x1e9/0x290 fs/dcache.c:750
Read of size 4 at addr ffff88810fd8add0 by task syz-executor/3339

CPU: 1 PID: 3339 Comm: syz-executor Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 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
 incfs_free_mount_info+0x60/0x200 fs/incfs/data_mgmt.c:166
 incfs_kill_sb+0x1aa/0x210 fs/incfs/vfs.c:1979
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x446/0x500 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+0xa4f/0x2480 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: 0033:0x7fc5bd35e749
Code: Unable to access opcode bytes at RIP 0x7fc5bd35e71f.
RSP: 002b:00007fff31b800f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fc5bd3e2ddd RCX: 00007fc5bd35e749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000009 R08: 00007fff31b7de97 R09: 00007fff31b813b0
R10: 0000000000000009 R11: 0000000000000246 R12: 00007fff31b813b0
R13: 00007fc5bd3e2d7d R14: 000055556886f4a8 R15: 00007fff31b82480

Allocated by task 6154:
 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+0x165/0x2e0 mm/slub.c:2965
 __d_alloc+0x2d/0x6a0 fs/dcache.c:1714
 d_alloc fs/dcache.c:1793 [inline]
 d_alloc_parallel+0xe1/0x1390 fs/dcache.c:2549
 __lookup_slow+0x13e/0x3e0 fs/namei.c:1633
 lookup_one_len+0x18e/0x2c0 fs/namei.c:2664
 incfs_lookup_dentry+0x60/0xb0 fs/incfs/data_mgmt.c:210
 open_or_create_special_dir+0x4f/0x1d0 fs/incfs/vfs.c:469
 incfs_mount_fs+0x434/0x8c0 fs/incfs/vfs.c:1867
 legacy_get_tree+0xed/0x190 fs/fs_context.c:593
 vfs_get_tree+0x89/0x260 fs/super.c:1572
 do_new_mount+0x25a/0xa20 fs/namespace.c:3006
 path_mount+0x572/0xc80 fs/namespace.c:3336
 do_mount fs/namespace.c:3349 [inline]
 __do_sys_mount fs/namespace.c:3557 [inline]
 __se_sys_mount+0x318/0x380 fs/namespace.c:3534
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3534
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 0:
 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+0x4df/0xa80 kernel/rcu/tree.c:2494
 rcu_core+0x55f/0xd60 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+0x10e/0x1050 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
 incfs_free_mount_info+0x60/0x200 fs/incfs/data_mgmt.c:166
 incfs_kill_sb+0x1aa/0x210 fs/incfs/vfs.c:1979
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x446/0x500 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+0xa4f/0x2480 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

Second to 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+0x10e/0x1050 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+0x235/0x620 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 ffff88810fd8add0
 which belongs to the cache dentry of size 208
The buggy address is located 0 bytes inside of
 208-byte region [ffff88810fd8add0, ffff88810fd8aea0)
The buggy address belongs to the page:
page:ffffea00043f6280 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10fd8a
flags: 0x4000000000000200(slab)
raw: 4000000000000200 dead000000000100 dead000000000122 ffff88810018b680
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 0x12cd0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_RECLAIMABLE), pid 107, ts 5094049517, free_ts 0
 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+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 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+0x1af/0x2e0 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
 do_unlinkat+0x17f/0x670 fs/namei.c:4031
 __do_sys_unlink fs/namei.c:4090 [inline]
 __se_sys_unlink fs/namei.c:4088 [inline]
 __x64_sys_unlink+0x49/0x50 fs/namei.c:4088
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88810fd8ac80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff88810fd8ad00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88810fd8ad80: fb fb fc fc fc fc fc fc fc fc fa fb fb fb fb fb
                                                 ^
 ffff88810fd8ae00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88810fd8ae80: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
==================================================================
------------[ cut here ]------------
WARNING: CPU: 0 PID: 3339 at fs/dcache.c:766 fast_dput+0x210/0x290 fs/dcache.c:766
Modules linked in:
CPU: 0 PID: 3339 Comm: syz-executor Tainted: G    B   W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:fast_dput+0x210/0x290 fs/dcache.c:766
Code: 03 f3 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 3a 03 f3 ff e9 8c fe ff ff e8 c0 14 b9 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:ffffc90001c97b80 EFLAGS: 00010293
RAX: ffffffff81aa8f80 RBX: ffff88810fd8add0 RCX: ffff888110c63b40
RDX: 0000000000000000 RSI: 00000000ffffff80 RDI: 0000000000000001
RBP: ffffc90001c97bb0 R08: 0000000000000004 R09: 0000000000000003
R10: fffff52000392f60 R11: 1ffff92000392f60 R12: 00000000ffffff80
R13: dffffc0000000000 R14: ffff88810fd8ae28 R15: 1ffff11021fb15c5
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007efd66031d58 CR3: 00000001181d3000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 dput+0x21/0x80 fs/dcache.c:870
 incfs_free_mount_info+0x60/0x200 fs/incfs/data_mgmt.c:166
 incfs_kill_sb+0x1aa/0x210 fs/incfs/vfs.c:1979
 deactivate_locked_super+0xa0/0x100 fs/super.c:335
 deactivate_super+0xaf/0xe0 fs/super.c:366
 cleanup_mnt+0x446/0x500 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+0xa4f/0x2480 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: 0033:0x7fc5bd35e749
Code: Unable to access opcode bytes at RIP 0x7fc5bd35e71f.
RSP: 002b:00007fff31b800f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fc5bd3e2ddd RCX: 00007fc5bd35e749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000001
RBP: 0000000000000009 R08: 00007fff31b7de97 R09: 00007fff31b813b0
R10: 0000000000000009 R11: 0000000000000246 R12: 00007fff31b813b0
R13: 00007fc5bd3e2d7d R14: 000055556886f4a8 R15: 00007fff31b82480
---[ end trace cd7fff5fb2ae7117 ]---

Crashes (22):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/12 11:33 android13-5.10-lts 9286af17ed5f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/12/09 13:57 android13-5.10-lts 9286af17ed5f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/12/03 19:50 android13-5.10-lts 9286af17ed5f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/12/01 23:53 android13-5.10-lts 9286af17ed5f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/11/26 08:32 android13-5.10-lts 9286af17ed5f 64219f15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/11/26 02:21 android13-5.10-lts 9286af17ed5f 64219f15 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/11/11 06:53 android13-5.10-lts ab3e1c0dd1ff 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/11/11 03:27 android13-5.10-lts ab3e1c0dd1ff 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/27 00:15 android13-5.10-lts 2ece552169c2 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/26 16:49 android13-5.10-lts 2ece552169c2 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/25 08:46 android13-5.10-lts 2ece552169c2 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/24 11:51 android13-5.10-lts 2ece552169c2 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/24 06:56 android13-5.10-lts 2ece552169c2 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/23 19:33 android13-5.10-lts 2ece552169c2 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/20 03:42 android13-5.10-lts 2ece552169c2 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/16 23:47 android13-5.10-lts 2ece552169c2 19568248 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/16 22:16 android13-5.10-lts 2ece552169c2 19568248 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/12 10:37 android13-5.10-lts 2ece552169c2 ff1712fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/09 08:12 android13-5.10-lts 2ece552169c2 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/08 14:38 android13-5.10-lts 2ece552169c2 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/10/04 14:25 android13-5.10-lts 0a91f603159e 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
2025/08/26 09:23 android13-5.10-lts 1154f779f3f3 bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in fast_dput
* Struck through repros no longer work on HEAD.