KASAN: use-after-free Read in ext4_convert_inline_data_nolock

Status: auto-obsoleted due to no activity on 2025/02/08 19:49
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+397f67bde5bd3d596c12@syzkaller.appspotmail.com
First crash: 812d, last: 657d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (5)
Date Name Commit Repro Result
2024/10/31 android13-5.15-lts (ToT) 5e4635681cf1 C [report] KASAN: use-after-free Read in ext4_convert_inline_data_nolock
2024/05/29 lts (merge base) 458ce51d0356 C [report] KASAN: use-after-free Read in ext4_convert_inline_data_nolock
2024/12/16 lts (merge base) 0a51d2d4527b C Didn't crash
2024/05/29 upstream (ToT) e0cce98fe279 C [report] KASAN: use-after-free Read in ext4_convert_inline_data_nolock
2024/10/31 upstream (ToT) 0fc810ae3ae1 C Didn't crash
▶ ▼ Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 KASAN: use-after-free Read in ext4_convert_inline_data_nolock origin:upstream 19 syz, C error 1 87d 1186d 0/3 upstream: reported C repro on 2023/05/21 13:36
upstream KASAN: slab-use-after-free Read in ext4_convert_inline_data_nolock ext4 19 syz, C error done 7 964d 1241d 25/29 fixed on 2024/02/03 12:44
android-5-10 KASAN: use-after-free Read in ext4_convert_inline_data_nolock 19 syz error 1 708d 841d 0/2 auto-obsoleted due to no activity on 2024/12/28 07:38
android-5-15 KASAN: use-after-free Read in ext4_convert_inline_data_nolock (2) 19 syz, C 7 12d 58d 0/2 upstream: reported C repro on 2026/06/22 03:50
android-6-1 KASAN: use-after-free Read in ext4_convert_inline_data_nolock origin:upstream missing-backport 19 syz, C done 2 645d 841d 0/2 auto-obsoleted due to no activity on 2025/02/20 23:05
android-5-10 KASAN: use-after-free Read in ext4_convert_inline_data_nolock (2) 19 syz, C 8 28d 59d 0/2 upstream: reported C repro on 2026/06/21 08:24
linux-6.1 KASAN: use-after-free Read in ext4_convert_inline_data_nolock origin:upstream 19 syz, C error 2 548d 1222d 0/3 upstream: reported C repro on 2023/04/15 09:27
android-6-1 KASAN: use-after-free Read in ext4_convert_inline_data_nolock (2) 19 syz, C 6 17d 19d 0/2 upstream: reported C repro on 2026/07/31 22:12
android-54 KASAN: use-after-free Read in ext4_convert_inline_data_nolock 19 syz, C 1 675d 841d 0/2 auto-obsoleted due to no activity on 2025/03/03 02:23
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2024/10/15 00:13 0m bisect fix android13-5.15-lts error job log
2024/09/03 05:10 38m bisect fix android13-5.15-lts OK (0) job log log
2024/07/29 14:20 1h48m bisect fix android13-5.15-lts 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_convert_inline_data_nolock+0x319/0xda0 fs/ext4/inline.c:1237
Read of size 68 at addr ffff88811eaa80cf by task syz-executor291/308

CPU: 1 PID: 308 Comm: syz-executor291 Not tainted 5.15.149-syzkaller-00055-g424f92bcbe8f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106
 print_address_description+0x87/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x179/0x1c0 mm/kasan/report.c:444
 kasan_check_range+0x293/0x2a0 mm/kasan/generic.c:189
 memcpy+0x2d/0x70 mm/kasan/shadow.c:65
 ext4_read_inline_data fs/ext4/inline.c:210 [inline]
 ext4_convert_inline_data_nolock+0x319/0xda0 fs/ext4/inline.c:1237
 ext4_try_add_inline_entry+0x7ff/0xb60 fs/ext4/inline.c:1363
 ext4_add_entry+0x6c2/0x12b0 fs/ext4/namei.c:2409
 ext4_mkdir+0x54f/0xce0 fs/ext4/namei.c:3032
 vfs_mkdir+0x3f6/0x610 fs/namei.c:4065
 do_mkdirat+0x1eb/0x450 fs/namei.c:4090
 __do_sys_mkdir fs/namei.c:4110 [inline]
 __se_sys_mkdir fs/namei.c:4108 [inline]
 __x64_sys_mkdir+0x6e/0x80 fs/namei.c:4108
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f36d6360587
Code: ff ff 77 07 31 c0 c3 0f 1f 40 00 48 c7 c2 b8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 b8 53 00 00 00 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:00007ffcc5753448 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f36d6360587
RDX: 0000000000000000 RSI: 00000000000001ff RDI: 0000000020000580
RBP: 0000000020000580 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000f4240 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffcc57534e0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

The buggy address belongs to the page:
page:ffffea00047aaa00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x11eaa8
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea00047ab748 ffffea0004474f08 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 0x100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 327, ts 35498273299, free_ts 35506324883
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2604
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2610
 get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4484
 __alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5776
 __alloc_pages_node include/linux/gfp.h:591 [inline]
 alloc_pages_node include/linux/gfp.h:605 [inline]
 alloc_pages include/linux/gfp.h:618 [inline]
 do_anonymous_page mm/memory.c:4032 [inline]
 handle_pte_fault+0xea0/0x24d0 mm/memory.c:4869
 do_handle_mm_fault+0x1ea9/0x23a0 mm/memory.c:5293
 handle_mm_fault include/linux/mm.h:1836 [inline]
 do_user_addr_fault arch/x86/mm/fault.c:1458 [inline]
 handle_page_fault arch/x86/mm/fault.c:1549 [inline]
 exc_page_fault+0x3b5/0x830 arch/x86/mm/fault.c:1605
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:568
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1471 [inline]
 free_pcp_prepare mm/page_alloc.c:1543 [inline]
 free_unref_page_prepare+0x7c8/0x7d0 mm/page_alloc.c:3533
 free_unref_page_list+0x14b/0xa60 mm/page_alloc.c:3670
 release_pages+0x1310/0x1370 mm/swap.c:1009
 free_pages_and_swap_cache+0x8a/0xa0 mm/swap_state.c:320
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu mm/mmu_gather.c:247 [inline]
 tlb_finish_mmu+0x177/0x320 mm/mmu_gather.c:338
 unmap_region+0x304/0x350 mm/mmap.c:2691
 __do_munmap+0x1421/0x1a90 mm/mmap.c:2925
 __vm_munmap+0x166/0x2a0 mm/mmap.c:2948
 __do_sys_munmap mm/mmap.c:2974 [inline]
 __se_sys_munmap mm/mmap.c:2970 [inline]
 __x64_sys_munmap+0x6b/0x80 mm/mmap.c:2970
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff88811eaa7f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88811eaa8000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88811eaa8080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88811eaa8100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88811eaa8180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop3): ext4_check_all_de:656: inode #12: block 5: comm syz-executor291: bad entry in directory: rec_len is smaller than minimal - offset=0, inode=0, rec_len=0, size=124 fake=0

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/05/29 02:54 android13-5.15-lts 424f92bcbe8f 34889ee3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci2-android-5-15 KASAN: use-after-free Read in ext4_convert_inline_data_nolock
* Struck through repros no longer work on HEAD.