KASAN: use-after-free Read in ext4_search_dir (2)

Status: fixed on 2024/10/22 11:57
Subsystems: ext4
[Documentation on labels]
Reported-by: syzbot+0c2508114d912a54ee79@syzkaller.appspotmail.com
Fix commit: c6b72f5d82b1 ext4: avoid OOB when system.data xattr changes underneath the filesystem
First crash: 705d, last: 681d
▶ ▼ Discussions (3)
Title Replies (including bot) Last reply
KASAN: slab-use-after-free Read in ext4_search_dir 1 (1) 2025/01/07 17:27
[PATCH 4/4] ext4: avoid OOB when system.data xattr changes underneath the filesystem 1 (1) 2024/08/21 15:23
[syzbot] [ext4?] KASAN: use-after-free Read in ext4_search_dir (2) 1 (3) 2024/08/20 14:23
▶ ▼ 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) ext4 prio:high actionable 19 1 21d 16d 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 C done 6 621d 981d 0/2 auto-obsoleted due to no activity on 2025/02/18 18:03
linux-5.15 KASAN: use-after-free Read in ext4_search_dir 19 C done 5 657d 1134d 3/3 fixed on 2024/11/08 17:20
android-54 KASAN: use-after-free Read in ext4_search_dir 19 C 17 662d 831d 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 C error done 20 929d 1170d 25/29 fixed on 2024/02/21 18:23
upstream KASAN: slab-out-of-bounds Read in ext4_search_dir ext4 19 C 5 212d 296d 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 C error error 29 186d 1006d 0/2 upstream: reported C repro on 2023/10/22 16:55
android-5-15 KASAN: use-after-free Read in ext4_search_dir 19 C 4 3d16h 34d 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 C error 24 34d 981d 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 C done 1 671d 1132d 0/3 upstream: reported C repro on 2023/06/18 19:29
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2024/08/20 14:02 19m cascardo@igalia.com patch git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 47ac09b91befbb6a235ab620c32af719f8208399 OK log

Sample crash report:
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
loop0: detected capacity change from 2048 to 2047
==================================================================
BUG: KASAN: use-after-free in ext4_search_dir+0xf2/0x1c0 fs/ext4/namei.c:1500
Read of size 1 at addr ffff88803e91130f by task syz-executor269/5103

CPU: 0 UID: 0 PID: 5103 Comm: syz-executor269 Not tainted 6.11.0-rc4-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 ext4_search_dir+0xf2/0x1c0 fs/ext4/namei.c:1500
 ext4_find_inline_entry+0x4be/0x5e0 fs/ext4/inline.c:1697
 __ext4_find_entry+0x2b4/0x1b30 fs/ext4/namei.c:1573
 ext4_lookup_entry fs/ext4/namei.c:1727 [inline]
 ext4_lookup+0x15f/0x750 fs/ext4/namei.c:1795
 lookup_one_qstr_excl+0x11f/0x260 fs/namei.c:1633
 filename_create+0x297/0x540 fs/namei.c:3980
 do_symlinkat+0xf9/0x3a0 fs/namei.c:4587
 __do_sys_symlinkat fs/namei.c:4610 [inline]
 __se_sys_symlinkat fs/namei.c:4607 [inline]
 __x64_sys_symlinkat+0x95/0xb0 fs/namei.c:4607
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3e73ced469
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 21 18 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff4d40c258 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 0032656c69662f2e RCX: 00007f3e73ced469
RDX: 0000000020000200 RSI: 00000000ffffff9c RDI: 00000000200001c0
RBP: 0000000000000000 R08: 00007fff4d40c290 R09: 00007fff4d40c290
R10: 0023706f6f6c2f76 R11: 0000000000000246 R12: 00007fff4d40c27c
R13: 0000000000000003 R14: 431bde82d7b634db R15: 00007fff4d40c2b0
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7fb7091d9 pfn:0x3e911
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 00000007fb7091d9 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), pid 5083, tgid 5083 (sshd), ts 84338308196, free_ts 84419190442
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1493
 prep_new_page mm/page_alloc.c:1501 [inline]
 get_page_from_freelist+0x2e4c/0x2f10 mm/page_alloc.c:3439
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4695
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2263
 folio_alloc_mpol_noprof mm/mempolicy.c:2281 [inline]
 vma_alloc_folio_noprof+0x12e/0x230 mm/mempolicy.c:2312
 folio_prealloc+0x31/0x170
 alloc_anon_folio mm/memory.c:4498 [inline]
 do_anonymous_page mm/memory.c:4555 [inline]
 do_pte_missing mm/memory.c:3945 [inline]
 handle_pte_fault+0x255e/0x6fc0 mm/memory.c:5521
 __handle_mm_fault mm/memory.c:5664 [inline]
 handle_mm_fault+0x1029/0x1980 mm/memory.c:5832
 do_user_addr_fault arch/x86/mm/fault.c:1338 [inline]
 handle_page_fault arch/x86/mm/fault.c:1481 [inline]
 exc_page_fault+0x459/0x8c0 arch/x86/mm/fault.c:1539
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5083 tgid 5083 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1094 [inline]
 free_unref_folios+0x103a/0x1b00 mm/page_alloc.c:2660
 folios_put_refs+0x76e/0x860 mm/swap.c:1039
 free_pages_and_swap_cache+0x2ea/0x690 mm/swap_state.c:332
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
 tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:373
 tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:465
 unmap_region+0x2df/0x350 mm/mmap.c:2441
 do_vmi_align_munmap+0x1122/0x18c0 mm/mmap.c:2754
 do_vmi_munmap+0x261/0x2f0 mm/mmap.c:2830
 __vm_munmap+0x1fc/0x400 mm/mmap.c:3109
 __do_sys_munmap mm/mmap.c:3126 [inline]
 __se_sys_munmap mm/mmap.c:3123 [inline]
 __x64_sys_munmap+0x68/0x80 mm/mmap.c:3123
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88803e911200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88803e911280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88803e911300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff88803e911380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88803e911400: 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
2024/08/19 07:25 upstream 47ac09b91bef e1c76ab2 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root KASAN: use-after-free Read in ext4_search_dir
2024/09/12 03:23 upstream 7c6a3a65ace7 d94c83d8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in ext4_search_dir
2024/09/07 11:38 upstream b31c44928842 9750182a .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in ext4_search_dir
2024/09/02 02:30 upstream c9f016e72b5c 1eda0d14 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: use-after-free Read in ext4_search_dir
2024/08/19 05:51 upstream 47ac09b91bef e1c76ab2 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in ext4_search_dir
* Struck through repros no longer work on HEAD.