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KASAN: use-after-free Read in ext4_read_inline_dir (2)

Status: upstream: reported C repro on 2024/12/31 16:48
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+ac63730e8e5e21567ff1@syzkaller.appspotmail.com
First crash: 378d, last: 2d22h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/01/04 lts (merge base) b67dc5c9ade9 C [report] KASAN: out-of-bounds Read in ext4_read_inline_dir
2025/01/04 upstream (ToT) 63676eefb7a0 C [report] KASAN: use-after-free Read in ext4_read_inline_data
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: use-after-free Read in ext4_read_inline_dir 19 1 533d 533d 0/2 auto-obsoleted due to no activity on 2024/10/28 03:11
android-5-15 KASAN: use-after-free Read in ext4_read_inline_dir origin:upstream 19 C 5 16d 372d 0/2 upstream: reported C repro on 2025/01/07 14:17
upstream KASAN: slab-out-of-bounds Read in ext4_read_inline_dir ext4 19 C done error 79 95d 535d 0/29 upstream: reported C repro on 2024/07/28 07:54
android-5-10 KASAN: slab-out-of-bounds Read in ext4_read_inline_dir 17 C error 2 21d 177d 0/2 upstream: reported C repro on 2025/07/21 09:03
▶ ▼ Last patch testing requests (4)
Created Duration User Patch Repo Result
2026/01/11 14:08 1h05m retest repro android14-6.1 report log
2026/01/11 14:08 21m retest repro android14-6.1 report log
2025/12/04 03:19 34m retest repro android14-6.1 report log
2025/12/04 03:19 15m retest repro android14-6.1 report log
▶ ▼ Fix bisection attempts (8)
Created Duration User Patch Repo Result
2025/11/19 13:58 1h34m bisect fix android14-6.1 OK (0) job log log
2025/10/17 12:53 1h38m bisect fix android14-6.1 OK (0) job log log
2025/08/25 17:49 2h42m bisect fix android14-6.1 OK (0) job log log
2025/07/22 19:46 1h35m bisect fix android14-6.1 OK (0) job log log
2025/06/03 11:48 1h10m bisect fix android14-6.1 OK (0) job log log
2025/05/03 10:22 2h10m bisect fix android14-6.1 OK (0) job log log
2025/03/19 00:24 1h00m bisect fix android14-6.1 OK (0) job log log
2025/02/15 19:22 51m bisect fix android14-6.1 OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in ext4_read_inline_data fs/ext4/inline.c:210 [inline]
BUG: KASAN: use-after-free in ext4_read_inline_dir+0x436/0xe50 fs/ext4/inline.c:1520
Read of size 68 at addr ffff88812942a6d3 by task syz-executor/368

CPU: 0 PID: 368 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106
 print_address_description+0x71/0x200 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:420
 kasan_report+0x122/0x150 mm/kasan/report.c:524
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x280/0x290 mm/kasan/generic.c:189
 memcpy+0x2d/0x70 mm/kasan/shadow.c:65
 ext4_read_inline_data fs/ext4/inline.c:210 [inline]
 ext4_read_inline_dir+0x436/0xe50 fs/ext4/inline.c:1520
 ext4_readdir+0x39a/0x3c10 fs/ext4/dir.c:161
 iterate_dir+0x271/0x610 fs/readdir.c:-1
 __do_sys_getdents64 fs/readdir.c:369 [inline]
 __se_sys_getdents64+0xe5/0x240 fs/readdir.c:354
 __x64_sys_getdents64+0x7b/0x90 fs/readdir.c:354
 x64_sys_call+0x15c/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:218
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0d441c20b3
Code: c1 66 0f 1f 44 00 00 48 83 c4 08 48 89 ef 5b 5d e9 62 3d f8 ff 66 90 b8 ff ff ff 7f 48 39 c2 48 0f 47 d0 b8 d9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 c7 c2 a8 ff ff ff f7 d8
RSP: 002b:00007ffe31e4e3c8 EFLAGS: 00000293 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 000055557d03d520 RCX: 00007f0d441c20b3
RDX: 0000000000008000 RSI: 000055557d03d520 RDI: 0000000000000006
RBP: 000055557d03d4f4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000293 R12: ffffffffffffffa8
R13: 0000000000000016 R14: 000055557d03d4f0 R15: 00007ffe31e51770
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0004a50a80 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x12942a
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004a50ac8 ffffea0004a50a48 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 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 337, tgid 337 (syz-executor), ts 27094928371, free_ts 27761833896
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2643
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2650
 get_page_from_freelist+0x2c7b/0x2cf0 mm/page_alloc.c:4554
 __alloc_pages+0x1c3/0x450 mm/page_alloc.c:5868
 __folio_alloc+0x12/0x40 mm/page_alloc.c:5900
 __folio_alloc_node include/linux/gfp.h:245 [inline]
 folio_alloc include/linux/gfp.h:274 [inline]
 alloc_page_vma include/linux/gfp.h:283 [inline]
 do_cow_fault mm/memory.c:4761 [inline]
 do_fault+0x4c0/0x1df0 mm/memory.c:4877
 handle_pte_fault mm/memory.c:5171 [inline]
 __handle_mm_fault mm/memory.c:5313 [inline]
 handle_mm_fault+0x12fa/0x2640 mm/memory.c:5453
 do_user_addr_fault+0x905/0x1050 arch/x86/mm/fault.c:1323
 handle_page_fault arch/x86/mm/fault.c:1466 [inline]
 exc_page_fault+0x51/0xb0 arch/x86/mm/fault.c:1522
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:608
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1551 [inline]
 free_pcp_prepare mm/page_alloc.c:1625 [inline]
 free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3589
 free_unref_page_list+0x112/0x8b0 mm/page_alloc.c:3740
 release_pages+0xad1/0xb20 mm/swap.c:1048
 free_pages_and_swap_cache+0x86/0xa0 mm/swap_state.c:315
 tlb_batch_pages_flush mm/mmu_gather.c:59 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:254 [inline]
 tlb_flush_mmu mm/mmu_gather.c:261 [inline]
 tlb_finish_mmu+0x1aa/0x370 mm/mmu_gather.c:361
 exit_mmap+0x3da/0xbb0 mm/mmap.c:3384
 __mmput+0x93/0x360 kernel/fork.c:1309
 mmput+0x4b/0x150 kernel/fork.c:1333
 exit_mm kernel/exit.c:568 [inline]
 do_exit+0x981/0x2650 kernel/exit.c:873
 do_group_exit+0x210/0x2d0 kernel/exit.c:1028
 get_signal+0x13b5/0x1520 kernel/signal.c:2889
 arch_do_signal_or_restart+0xb0/0x1030 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x7a/0xb0 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87

Memory state around the buggy address:
 ffff88812942a580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812942a600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812942a680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                 ^
 ffff88812942a700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812942a780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop5): ext4_read_inline_dir:1601: inode #12: block 7: comm syz-executor: path /0/file1/file0: bad entry in directory: rec_len % 4 != 0 - offset=24, inode=2239623941, rec_len=29527, size=148 fake=0
EXT4-fs error (device loop5): ext4_read_inline_dir:1601: inode #12: block 7: comm syz-executor: path /0/file1/file0: bad entry in directory: rec_len % 4 != 0 - offset=24, inode=2239623941, rec_len=29527, size=148 fake=0
EXT4-fs error (device loop5): empty_inline_dir:1885: inode #12: block 7: comm syz-executor: bad entry in directory: rec_len % 4 != 0 - offset=4, inode=2239623941, rec_len=29527, size=60 fake=0
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs error (device loop5): ext4_read_inline_dir:1601: inode #12: block 7: comm syz-executor: path /0/file1/file0: bad entry in directory: rec_len % 4 != 0 - offset=24, inode=2239623941, rec_len=29527, size=148 fake=0
EXT4-fs error (device loop5): ext4_read_inline_dir:1601: inode #12: block 7: comm syz-executor: path /0/file1/file0: bad entry in directory: rec_len % 4 != 0 - offset=24, inode=2239623941, rec_len=29527, size=148 fake=0
EXT4-fs error (device loop5): empty_inline_dir:1885: inode #12: block 7: comm syz-executor: bad entry in directory: rec_len % 4 != 0 - offset=4, inode=2239623941, rec_len=29527, size=60 fake=0
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs error (device loop5): ext4_read_inline_dir:1601: inode #12: block 7: comm syz-executor: path /0/file1/file0: bad entry in directory: rec_len % 4 != 0 - offset=24, inode=2239623941, rec_len=29527, size=148 fake=0
EXT4-fs error (device loop5): ext4_read_inline_dir:1601: inode #12: block 7: comm syz-executor: path /0/file1/file0: bad entry in directory: rec_len % 4 != 0 - offset=24, inode=2239623941, rec_len=29527, size=148 fake=0
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs warning (device loop5): empty_inline_dir:1892: bad inline directory (dir #12) - inode 2239623941, rec_len 29527, name_len 58inline size 60
EXT4-fs (loop5): unmounting filesystem.

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/28 10:30 android14-6.1 5e6db7045704 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in ext4_read_inline_dir
2024/12/31 17:40 android14-6.1 e2b9748880b9 d3ccff63 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-6-1 KASAN: use-after-free Read in ext4_read_inline_dir
2024/12/31 16:46 android14-6.1 e2b9748880b9 d3ccff63 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-6-1 KASAN: use-after-free Read in ext4_read_inline_dir
2025/12/28 11:00 android14-6.1 5e6db7045704 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: slab-out-of-bounds Read in ext4_read_inline_dir
2024/12/31 17:09 android14-6.1 e2b9748880b9 d3ccff63 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-6-1 KASAN: out-of-bounds Read in ext4_read_inline_dir
* Struck through repros no longer work on HEAD.