KASAN: use-after-free Read in ext4_search_dir

Status: fixed on 2024/11/08 17:20
Reported-by: syzbot+49e1219c6cb561ada5b9@syzkaller.appspotmail.com
Fix commit: be2e9b111e27 ext4: avoid OOB when system.data xattr changes underneath the filesystem
First crash: 1155d, last: 677d
Fix bisection: fixed by (bisect log) :
commit be2e9b111e2790962cc66a177869b4e9717b4e29
Author: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Date: Wed Aug 21 15:23:24 2024 +0000

  ext4: avoid OOB when system.data xattr changes underneath the filesystem

  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2024/10/28 upstream (ToT) 819837584309 C Didn't crash
▶ ▼ Similar bugs (10)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in ext4_search_dir (3) prio:high actionable ext4 19 2 12d 36d 0/29 upstream: reported on 2026/07/09 00:07
android-5-15 KASAN: slab-out-of-bounds Read in ext4_search_dir origin:upstream missing-backport 19 syz, C done 6 642d 1001d 0/2 auto-obsoleted due to no activity on 2025/02/18 18:03
android-54 KASAN: use-after-free Read in ext4_search_dir 19 syz, C 17 682d 851d 0/2 auto-obsoleted due to no activity on 2025/02/18 14:16
upstream KASAN: use-after-free Read in ext4_search_dir prio:low ext4 19 syz, C error done 20 950d 1191d 25/29 fixed on 2024/02/21 18:23
upstream KASAN: slab-out-of-bounds Read in ext4_search_dir ext4 19 syz, C 5 232d 316d 29/29 fixed on 2026/05/06 16:40
android-6-1 KASAN: use-after-free Read in ext4_search_dir missing-backport origin:upstream 19 syz, C error error 32 13d 1027d 0/2 upstream: reported C repro on 2023/10/22 16:55
android-5-15 KASAN: use-after-free Read in ext4_search_dir origin:upstream 19 syz, C 4 24d 54d 0/2 upstream: reported C repro on 2026/06/21 07:51
android-5-10 KASAN: slab-out-of-bounds Read in ext4_search_dir 19 syz, C error 24 54d 1001d 0/2 upstream: reported C repro on 2023/11/17 09:38
linux-6.1 KASAN: use-after-free Read in ext4_search_dir origin:upstream missing-backport 19 syz, C done 1 692d 1153d 0/3 upstream: reported C repro on 2023/06/18 19:29
upstream KASAN: use-after-free Read in ext4_search_dir (2) ext4 19 syz, C 5 701d 725d 28/29 fixed on 2024/10/22 11:57
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2024/10/04 00:17 11m retest repro linux-5.15.y report log
▶ ▼ Fix bisection attempts (13)
Created Duration User Patch Repo Result
2024/11/08 12:57 4h18m bisect fix linux-5.15.y OK (1) job log
2024/09/08 04:29 47m bisect fix linux-5.15.y OK (0) job log log
2024/08/06 04:59 1h44m bisect fix linux-5.15.y OK (0) job log log
2024/06/27 04:18 50m bisect fix linux-5.15.y OK (0) job log log
2024/05/19 13:11 55m bisect fix linux-5.15.y OK (0) job log log
2024/04/13 21:39 1h13m bisect fix linux-5.15.y OK (0) job log log
2024/03/11 19:15 48m bisect fix linux-5.15.y OK (0) job log log
2024/02/05 10:49 1h18m bisect fix linux-5.15.y OK (0) job log log
2023/12/31 21:15 54m bisect fix linux-5.15.y OK (0) job log log
2023/12/01 16:17 56m bisect fix linux-5.15.y OK (0) job log log
2023/10/31 04:00 1h08m bisect fix linux-5.15.y OK (0) job log log
2023/09/30 18:26 52m bisect fix linux-5.15.y OK (0) job log log
2023/07/31 13:44 1h22m bisect fix linux-5.15.y OK (0) job log log

Sample crash report:
EXT4-fs (loop0): mounted filesystem without journal. Opts: ,errors=continue. Quota mode: none.
==================================================================
BUG: KASAN: use-after-free in ext4_search_dir+0xee/0x1b0 fs/ext4/namei.c:1544
Read of size 1 at addr ffff88805d4424ff by task syz.0.832/7302

CPU: 1 PID: 7302 Comm: syz.0.832 Not tainted 5.15.167-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 print_address_description+0x63/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0x16b/0x1c0 mm/kasan/report.c:451
 ext4_search_dir+0xee/0x1b0 fs/ext4/namei.c:1544
 ext4_find_inline_entry+0x4b6/0x5e0 fs/ext4/inline.c:1704
 __ext4_find_entry+0x2b0/0x1b20 fs/ext4/namei.c:1617
 ext4_lookup_entry fs/ext4/namei.c:1772 [inline]
 ext4_lookup+0x3c6/0xaa0 fs/ext4/namei.c:1840
 __lookup_slow+0x275/0x3d0 fs/namei.c:1663
 lookup_slow+0x53/0x70 fs/namei.c:1680
 walk_component+0x48c/0x610 fs/namei.c:1976
 lookup_last fs/namei.c:2431 [inline]
 path_lookupat+0x16f/0x450 fs/namei.c:2455
 filename_lookup+0x230/0x5c0 fs/namei.c:2484
 user_path_at_empty+0x40/0x180 fs/namei.c:2883
 user_path_at include/linux/namei.h:57 [inline]
 __do_sys_chdir fs/open.c:490 [inline]
 __se_sys_chdir+0xbb/0x220 fs/open.c:484
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f903029bff9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f902e714038 EFLAGS: 00000246 ORIG_RAX: 0000000000000050
RAX: ffffffffffffffda RBX: 00007f9030453f80 RCX: 00007f903029bff9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000000
RBP: 00007f903030e296 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9030453f80 R15: 00007ffc2caf8728
 </TASK>

The buggy address belongs to the page:
page:ffffea0001751080 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x5d442
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea00017510c8 ffffea0001751048 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x1100cca(GFP_HIGHUSER_MOVABLE), pid 7307, ts 299947141703, free_ts 300896369148
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x322a/0x33c0 mm/page_alloc.c:4159
 __alloc_pages+0x272/0x700 mm/page_alloc.c:5423
 alloc_pages_vma+0x39a/0x800 mm/mempolicy.c:2146
 shmem_alloc_page mm/shmem.c:1586 [inline]
 shmem_alloc_and_acct_page+0x4d1/0xd10 mm/shmem.c:1611
 shmem_getpage_gfp+0x17b1/0x3190 mm/shmem.c:1906
 shmem_fault+0x1d7/0x700 mm/shmem.c:2118
 __do_fault+0x139/0x340 mm/memory.c:3898
 do_read_fault mm/memory.c:4234 [inline]
 do_fault mm/memory.c:4362 [inline]
 handle_pte_fault mm/memory.c:4620 [inline]
 __handle_mm_fault mm/memory.c:4755 [inline]
 handle_mm_fault+0x376f/0x5960 mm/memory.c:4853
 faultin_page mm/gup.c:976 [inline]
 __get_user_pages+0x4ed/0x11d0 mm/gup.c:1197
 populate_vma_page_range+0x215/0x2a0 mm/gup.c:1529
 __mm_populate+0x2a5/0x4a0 mm/gup.c:1638
 mm_populate include/linux/mm.h:2632 [inline]
 vm_mmap_pgoff+0x22b/0x2d0 mm/util.c:556
 ksys_mmap_pgoff+0x13e/0x780 mm/mmap.c:1624
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0xc34/0xcf0 mm/page_alloc.c:3317
 free_unref_page_list+0x1f7/0x8e0 mm/page_alloc.c:3433
 release_pages+0x1bb9/0x1f40 mm/swap.c:963
 __pagevec_release+0x80/0xf0 mm/swap.c:983
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x67a/0x1b50 mm/shmem.c:964
 shmem_truncate_range mm/shmem.c:1063 [inline]
 shmem_evict_inode+0x21b/0xa00 mm/shmem.c:1145
 evict+0x529/0x930 fs/inode.c:622
 __dentry_kill+0x436/0x650 fs/dcache.c:586
 dentry_kill+0xbb/0x290
 dput+0xd8/0x1a0 fs/dcache.c:893
 __fput+0x636/0x8e0 fs/file_table.c:288
 task_work_run+0x129/0x1a0 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0x6a3/0x2480 kernel/exit.c:874
 do_group_exit+0x144/0x310 kernel/exit.c:996
 get_signal+0xc66/0x14e0 kernel/signal.c:2897
 arch_do_signal_or_restart+0xc3/0x1890 arch/x86/kernel/signal.c:867

Memory state around the buggy address:
 ffff88805d442380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805d442400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805d442480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                                ^
 ffff88805d442500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805d442580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/10/06 08:16 linux-5.15.y 3a5928702e71 d7906eff .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in ext4_search_dir
2024/10/06 01:57 linux-5.15.y 3a5928702e71 d7906eff .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in ext4_search_dir
2024/09/19 03:59 linux-5.15.y 3a5928702e71 c673ca06 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci2-linux-5-15-kasan KASAN: use-after-free Read in ext4_search_dir
2024/09/19 01:24 linux-5.15.y 3a5928702e71 c673ca06 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan KASAN: use-after-free Read in ext4_search_dir
2023/06/16 15:51 linux-5.15.y 471e639e59d1 f3921d4d .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci2-linux-5-15-kasan KASAN: use-after-free Read in ext4_search_dir
* Struck through repros no longer work on HEAD.