KASAN: use-after-free Read in __ext4_check_dir_entry (2)

Status: upstream: reported C repro on 2024/05/14 14:09
Subsystems: ext4
[Documentation on labels]
First crash: 42d, last: 28d
Cause bisection: failed (error log, bisect log)
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [ext4?] KASAN: use-after-free Read in __ext4_check_dir_entry (2) 0 (3) 2024/05/16 18:51
Similar bugs (7)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.14 KASAN: use-after-free Read in __ext4_check_dir_entry C inconclusive 6 1367d 1471d 0/1 upstream: reported C repro on 2020/06/12 02:23
linux-5.15 KASAN: use-after-free Read in __ext4_check_dir_entry origin:upstream C 8 13d 19d 0/3 upstream: reported C repro on 2024/06/03 01:15
android-5-15 KASAN: use-after-free Read in __ext4_check_dir_entry origin:downstream syz 2 2d09h 7d16h 0/2 premoderation: reported syz repro on 2024/06/14 16:50
upstream KASAN: use-after-free Read in __ext4_check_dir_entry ext4 C 8 2271d 2274d 22/27 closed as dup on 2018/03/31 22:38
android-5-10 KASAN: use-after-free Read in __ext4_check_dir_entry C 1 28d 43d 0/2 upstream: reported C repro on 2024/05/10 09:19
android-6-1 KASAN: use-after-free Read in __ext4_check_dir_entry origin:upstream C 4 21d 41d 0/2 upstream: reported C repro on 2024/05/11 11:53
linux-6.1 KASAN: use-after-free Read in __ext4_check_dir_entry 6 13d 19d 0/3 upstream: reported on 2024/06/03 01:12
Last patch testing requests (3)
Created Duration User Patch Repo Result
2024/05/24 14:15 1h03m retest repro upstream report log
2024/05/16 18:51 18m git:// origin error OK
2024/05/15 23:01 22m git:// dev error OK

Sample crash report:
EXT4-fs error (device loop0): make_indexed_dir:2282: inode #2: block 255: comm syz-executor396: bad entry in directory: rec_len is smaller than minimal - offset=0, inode=5120, rec_len=0, size=993 fake=0
EXT4-fs warning (device loop0): dx_probe:832: inode #2: comm syz-executor396: Unrecognised inode hash code 49
EXT4-fs warning (device loop0): dx_probe:965: inode #2: comm syz-executor396: Corrupt directory, running e2fsck is recommended
BUG: KASAN: use-after-free in __ext4_check_dir_entry+0x6fd/0x880 fs/ext4/dir.c:85
Read of size 2 at addr ffff8880683ae003 by task syz-executor396/5071

CPU: 0 PID: 5071 Comm: syz-executor396 Not tainted 6.9.0-rc7-syzkaller-00117-g448b3fe5a0ea #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 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_check_dir_entry+0x6fd/0x880 fs/ext4/dir.c:85
 ext4_readdir+0x145d/0x3800 fs/ext4/dir.c:258
 iterate_dir+0x539/0x6f0 fs/readdir.c:110
 __do_sys_getdents64 fs/readdir.c:409 [inline]
 __se_sys_getdents64+0x20d/0x4f0 fs/readdir.c:394
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
RIP: 0033:0x7f8311a13ed9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 19 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:00007ffd43d6adc8 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007ffd43d6ae10 RCX: 00007f8311a13ed9
RDX: 0000000000000010 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007ffd43d6ae18 R08: 000055556bcad0c0 R09: 000055556bcad0c0
R10: 000055556bcad0c0 R11: 0000000000000246 R12: 00007f8311a906a0
R13: 00007ffd43d6ae10 R14: 0000000000000004 R15: 0000000000000003

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x683ae
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 ffffea0001a0ebc8 ffff8880b9444570 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), pid 5065, tgid -1706810074 (sftp-server), ts 5065, free_ts 54138803695
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1534
 prep_new_page mm/page_alloc.c:1541 [inline]
 get_page_from_freelist+0x3410/0x35b0 mm/page_alloc.c:3317
 __alloc_pages+0x256/0x6c0 mm/page_alloc.c:4575
 alloc_pages_mpol+0x3e8/0x680 mm/mempolicy.c:2264
 vma_alloc_folio+0xf3/0x1f0 mm/mempolicy.c:2303
 alloc_anon_folio mm/memory.c:4375 [inline]
 do_anonymous_page mm/memory.c:4433 [inline]
 do_pte_missing mm/memory.c:3878 [inline]
 handle_pte_fault mm/memory.c:5300 [inline]
 __handle_mm_fault+0x3a03/0x7250 mm/memory.c:5441
 handle_mm_fault+0x27f/0x770 mm/memory.c:5606
 do_user_addr_fault arch/x86/mm/fault.c:1331 [inline]
 handle_page_fault arch/x86/mm/fault.c:1474 [inline]
 exc_page_fault+0x446/0x8a0 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5065 tgid 5065 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1141 [inline]
 free_unref_page_prepare+0x97b/0xaa0 mm/page_alloc.c:2347
 free_unref_folios+0x1f2/0xc10 mm/page_alloc.c:2536
 folios_put_refs+0x93a/0xa60 mm/swap.c:1034
 free_pages_and_swap_cache+0x2ea/0x690 mm/swap_state.c:329
 __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
 exit_mmap+0x4bb/0xd60 mm/mmap.c:3280
 __mmput+0x115/0x3c0 kernel/fork.c:1346
 exit_mm+0x220/0x310 kernel/exit.c:569
 do_exit+0x99e/0x27e0 kernel/exit.c:865
 do_group_exit+0x207/0x2c0 kernel/exit.c:1027
 __do_sys_exit_group kernel/exit.c:1038 [inline]
 __se_sys_exit_group kernel/exit.c:1036 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1036
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83

Memory state around the buggy address:
 ffff8880683adf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880683adf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880683ae000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880683ae080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880683ae100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/05/10 13:58 upstream 448b3fe5a0ea de979bc2 .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs KASAN: use-after-free Read in __ext4_check_dir_entry
* Struck through repros no longer work on HEAD.