KASAN: use-after-free Read in ext4_htree_fill_tree

Status: upstream: reported C repro on 2024/12/27 19:48
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+254e41833ea7ee21fe91@syzkaller.appspotmail.com
First crash: 579d, last: 106d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (4)
Date Name Commit Repro Result
2025/05/12 android13-5.15-lts (ToT) 57725b368731 C [report] KASAN: slab-out-of-bounds Read in ext4_htree_fill_tree
2025/01/03 lts (merge base) 9467c49437e9 C [report] KASAN: use-after-free Read in ext4_htree_fill_tree
2025/01/03 upstream (ToT) 0bc21e701a6f C [report] KASAN: slab-out-of-bounds Read in ext4_htree_fill_tree
2025/05/12 upstream (ToT) 82f2b0b97b36 C Didn't crash
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: use-after-free Read in ext4_htree_fill_tree missing-backport origin:upstream 19 syz, C error 9 94d 584d 0/2 upstream: reported C repro on 2024/12/22 19:07
linux-6.1 KASAN: use-after-free Read in ext4_htree_fill_tree 19 1 684d 684d 0/3 auto-obsoleted due to no activity on 2024/12/22 07:44
android-5-10 KASAN: slab-out-of-bounds Read in ext4_htree_fill_tree 19 syz, C 14 21d 738d 0/2 upstream: reported C repro on 2024/07/21 20:19
▶ ▼ Last patch testing requests (9)
Created Duration User Patch Repo Result
2026/06/30 10:34 15m retest repro android13-5.15-lts log
2026/06/30 10:34 13m retest repro android13-5.15-lts log
2026/06/30 10:34 11m retest repro android13-5.15-lts log
2026/06/13 00:04 14m retest repro android13-5.15-lts log
2026/06/05 22:28 2h00m retest repro android13-5.15-lts log
2026/06/05 22:28 16m retest repro android13-5.15-lts log
2026/05/16 23:11 13m retest repro android13-5.15-lts log
2026/05/16 23:11 13m retest repro android13-5.15-lts log
2026/04/15 03:18 6m retest repro android13-5.15-lts report log

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in ext4_htree_fill_tree+0x131b/0x13e0 fs/ext4/namei.c:1246
Read of size 1 at addr ffff88812496fd1b by task syz-executor211/301

CPU: 0 PID: 301 Comm: syz-executor211 Not tainted 5.15.176-syzkaller-00972-g829d9f138569 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1c0 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
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:306
 ext4_htree_fill_tree+0x131b/0x13e0 fs/ext4/namei.c:1246
 ext4_dx_readdir fs/ext4/dir.c:606 [inline]
 ext4_readdir+0x2f75/0x3960 fs/ext4/dir.c:142
 iterate_dir+0x265/0x600
 __do_sys_getdents64 fs/readdir.c:369 [inline]
 __se_sys_getdents64+0x1c1/0x460 fs/readdir.c:354
 __x64_sys_getdents64+0x7b/0x90 fs/readdir.c:354
 x64_sys_call+0x5ae/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:218
 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: 0033:0x7f87e962c2f3
Code: c1 66 0f 1f 44 00 00 48 83 c4 08 48 89 ef 5b 5d e9 62 47 fb 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 b8 ff ff ff f7 d8
RSP: 002b:00007ffd827eef98 EFLAGS: 00000293 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 000055557b4d6730 RCX: 00007f87e962c2f3
RDX: 0000000000008000 RSI: 000055557b4d6730 RDI: 0000000000000004
RBP: 000055557b4d6704 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000001000 R11: 0000000000000293 R12: ffffffffffffffb8
R13: 0000000000000010 R14: 000055557b4d6700 R15: 00007ffd827f1210
 </TASK>

The buggy address belongs to the page:
page:ffffea0004925bc0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x12496f
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004925c08 ffffea0004925b88 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 278, ts 22666901509, free_ts 22727872431
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4485
 __alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5780
 __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:4066 [inline]
 handle_pte_fault+0xe7e/0x25c0 mm/memory.c:4903
 do_handle_mm_fault+0x20bc/0x2400 mm/memory.c:5327
 handle_mm_fault include/linux/mm.h:1836 [inline]
 do_user_addr_fault arch/x86/mm/fault.c:1418 [inline]
 handle_page_fault arch/x86/mm/fault.c:1509 [inline]
 exc_page_fault+0x3b5/0x7f0 arch/x86/mm/fault.c:1565
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:606
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1472 [inline]
 free_pcp_prepare mm/page_alloc.c:1544 [inline]
 free_unref_page_prepare+0x7c8/0x7d0 mm/page_alloc.c:3534
 free_unref_page_list+0x14b/0xa60 mm/page_alloc.c:3671
 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:2680
 __do_munmap+0x13e4/0x19d0 mm/mmap.c:2913
 __vm_munmap+0x166/0x2a0 mm/mmap.c:2966
 __do_sys_munmap mm/mmap.c:2992 [inline]
 __se_sys_munmap mm/mmap.c:2988 [inline]
 __x64_sys_munmap+0x6b/0x80 mm/mmap.c:2988
 x64_sys_call+0x75/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:12
 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

Memory state around the buggy address:
 ffff88812496fc00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812496fc80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812496fd00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff88812496fd80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812496fe00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop3): __ext4_get_inode_loc:4351: comm syz-executor211: Invalid inode table block 14875662660405297151 in block_group 0
EXT4-fs error (device loop3) in ext4_reserve_inode_write:5837: Corrupt filesystem
EXT4-fs error (device loop3): ext4_dirty_inode:6041: inode #2: comm syz-executor211: mark_inode_dirty error

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/01/21 01:40 android13-5.15-lts 829d9f138569 6e87cfa2 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: use-after-free Read in ext4_htree_fill_tree
2024/12/27 23:11 android13-5.15-lts b4bd207b0380 d3ccff63 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: use-after-free Read in ext4_htree_fill_tree
2024/12/27 21:13 android13-5.15-lts b4bd207b0380 d3ccff63 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: use-after-free Read in ext4_htree_fill_tree
2024/12/27 19:46 android13-5.15-lts b4bd207b0380 d3ccff63 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: use-after-free Read in ext4_htree_fill_tree
2025/02/18 21:45 android13-5.15-lts 058abb720bd1 c37c7249 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (corrupt fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_htree_fill_tree
2025/02/05 21:49 android13-5.15-lts d1a25a6a4b3b 4dc70884 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: use-after-free Read in ext4_htree_fill_tree
2024/12/28 01:22 android13-5.15-lts b4bd207b0380 d3ccff63 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: use-after-free Read in ext4_htree_fill_tree
2025/04/02 11:30 android13-5.15-lts 5e1b899f19c3 c799dfdd .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: slab-out-of-bounds Read in ext4_htree_fill_tree
2025/03/06 05:58 android13-5.15-lts 7d1f9b5c2ff5 831e3629 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: slab-out-of-bounds Read in ext4_htree_fill_tree
* Struck through repros no longer work on HEAD.