syzbot


KASAN: use-after-free Read in __ext4_check_dir_entry

Status: upstream: reported C repro on 2024/05/11 11:53
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+3f08b9d4d6ca05d557f8@syzkaller.appspotmail.com
First crash: 42d, last: 22d
Bug presence (2)
Date Name Commit Repro Result
2024/05/11 lts (merge base) 883d1a956208 C [report] KASAN: use-after-free Read in __ext4_check_dir_entry
2024/05/11 upstream (ToT) cf87f46fd34d C [report] KASAN: use-after-free Read in __ext4_check_dir_entry
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 1368d 1472d 0/1 upstream: reported C repro on 2020/06/12 02:23
upstream KASAN: use-after-free Read in __ext4_check_dir_entry (2) ext4 C error 1 29d 39d 0/27 upstream: reported C repro on 2024/05/14 14:09
linux-5.15 KASAN: use-after-free Read in __ext4_check_dir_entry origin:upstream C 8 14d 20d 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 3d07h 8d15h 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 2272d 2275d 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 29d 43d 0/2 upstream: reported C repro on 2024/05/10 09:19
linux-6.1 KASAN: use-after-free Read in __ext4_check_dir_entry 6 14d 20d 0/3 upstream: reported on 2024/06/03 01:12
Last patch testing requests (1)
Created Duration User Patch Repo Result
2024/05/25 11:55 10m retest repro android14-6.1 report log

Sample crash report:
EXT4-fs warning (device loop0): dx_probe:832: inode #2: comm syz-executor231: Unrecognised inode hash code 49
EXT4-fs warning (device loop0): dx_probe:965: inode #2: comm syz-executor231: Corrupt directory, running e2fsck is recommended
==================================================================
BUG: KASAN: use-after-free in __ext4_check_dir_entry+0x700/0x880 fs/ext4/dir.c:85
Read of size 2 at addr ffff8881217cb003 by task syz-executor231/300

CPU: 1 PID: 300 Comm: syz-executor231 Not tainted 6.1.75-syzkaller-00003-g4d55129aea65 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0x158/0x4e0 mm/kasan/report.c:427
 kasan_report+0x13c/0x170 mm/kasan/report.c:531
 __asan_report_load2_noabort+0x14/0x20 mm/kasan/report_generic.c:349
 __ext4_check_dir_entry+0x700/0x880 fs/ext4/dir.c:85
 ext4_readdir+0x1386/0x3930 fs/ext4/dir.c:258
 iterate_dir+0x265/0x610
 __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
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f3f8b08c0e9
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:00007ffc4c3447a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f3f8b08c0e9
RDX: 0000000000000010 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 0000000000000000 R08: 00007ffc4c3447dc R09: 00007ffc4c3447dc
R10: 00007ffc4c3447dc R11: 0000000000000246 R12: 00007ffc4c3447dc
R13: 0000000000000001 R14: 431bde82d7b634db R15: 00007ffc4c344810
 </TASK>

The buggy address belongs to the physical page:
page:ffffea000485f2c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1217cb
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea000485f308 ffff8881f703bb68 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 0x8140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO|__GFP_CMA), pid 235, tgid 235 (sshd), ts 14746125651, free_ts 14770395574
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x213/0x220 mm/page_alloc.c:2590
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2597
 get_page_from_freelist+0x27ea/0x2870 mm/page_alloc.c:4425
 __alloc_pages+0x3a1/0x780 mm/page_alloc.c:5712
 __folio_alloc+0x15/0x40 mm/page_alloc.c:5744
 __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_anonymous_page mm/memory.c:4219 [inline]
 handle_pte_fault mm/memory.c:5094 [inline]
 __handle_mm_fault mm/memory.c:5238 [inline]
 handle_mm_fault+0x1fb0/0x2f40 mm/memory.c:5378
 do_user_addr_fault arch/x86/mm/fault.c:1363 [inline]
 handle_page_fault arch/x86/mm/fault.c:1506 [inline]
 exc_page_fault+0x3b3/0x700 arch/x86/mm/fault.c:1562
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:570
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1498 [inline]
 free_pcp_prepare mm/page_alloc.c:1572 [inline]
 free_unref_page_prepare+0x83d/0x850 mm/page_alloc.c:3498
 free_unref_page_list+0xf1/0x7b0 mm/page_alloc.c:3646
 release_pages+0xf7f/0xfe0 mm/swap.c:1063
 free_pages_and_swap_cache+0x8a/0xa0 mm/swap_state.c:314
 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+0x1e0/0x3f0 mm/mmu_gather.c:361
 unmap_region+0x2c1/0x310 mm/mmap.c:2405
 do_mas_align_munmap+0xd05/0x1400 mm/mmap.c:2672
 do_mas_munmap+0x23e/0x2b0 mm/mmap.c:2730
 __vm_munmap+0x263/0x3a0 mm/mmap.c:3020
 __do_sys_munmap mm/mmap.c:3046 [inline]
 __se_sys_munmap mm/mmap.c:3042 [inline]
 __x64_sys_munmap+0x6b/0x80 mm/mmap.c:3042
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Memory state around the buggy address:
 ffff8881217caf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881217caf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8881217cb000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8881217cb080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881217cb100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop0): ext4_readdir:260: inode #2: block 255: comm syz-executor231: path /root/syzkaller.uT7fTt/1/file0: bad entry in directory: directory entry overrun - offset=1023, inode=542842880, rec_len=8224, size=1024 fake=0

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/05/11 11:52 android14-6.1 4d55129aea65 9026e142 .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-6-1 KASAN: use-after-free Read in __ext4_check_dir_entry
2024/06/01 04:43 android14-6.1 92704e00b599 3113787f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in __ext4_check_dir_entry
2024/06/01 04:42 android14-6.1 92704e00b599 3113787f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in __ext4_check_dir_entry
2024/06/01 04:42 android14-6.1 92704e00b599 3113787f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-1 KASAN: use-after-free Read in __ext4_check_dir_entry
* Struck through repros no longer work on HEAD.