[syzbot] [ext4?] KASAN: use-after-free Read in __ext4_check_dir_entry (3)

From: syzbot
Date: Sun Oct 06 2024 - 13:11:35 EST

Hello,

syzbot found the following issue on:

HEAD commit: e32cde8d2bd7 Merge tag 'sched_ext-for-6.12-rc1-fixes-1' of..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17219927980000
kernel config: https://syzkaller.appspot.com/x/.config?x=1f009dd80b3799c2
dashboard link: https://syzkaller.appspot.com/bug?extid=09921540dd04aba82a35
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=102f23d0580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1082e580580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/08f3ba449e03/disk-e32cde8d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/17bcace1ab90/vmlinux-e32cde8d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/da9183ac0145/bzImage-e32cde8d.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/45cde0725f07/mount_0.gz

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14ba5927980000
final oops: https://syzkaller.appspot.com/x/report.txt?x=16ba5927980000
console output: https://syzkaller.appspot.com/x/log.txt?x=12ba5927980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+09921540dd04aba82a35@xxxxxxxxxxxxxxxxxxxxxxxxx

EXT4-fs error (device loop0): ext4_orphan_get:1393: comm syz-executor400: couldn't read orphan inode 15 (err -117)
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
EXT4-fs warning (device loop0): dx_probe:833: inode #2: comm syz-executor400: Unrecognised inode hash code 4
EXT4-fs warning (device loop0): dx_probe:966: inode #2: comm syz-executor400: 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 ffff88807fc17003 by task syz-executor400/5217

CPU: 0 UID: 0 PID: 5217 Comm: syz-executor400 Not tainted 6.12.0-rc1-syzkaller-00031-ge32cde8d2bd7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
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+0x1436/0x3a60 fs/ext4/dir.c:259
iterate_dir+0x571/0x800 fs/readdir.c:108
__do_sys_getdents64 fs/readdir.c:407 [inline]
__se_sys_getdents64+0x1d3/0x4a0 fs/readdir.c:392
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcfd760b6d9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 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:00007ffe192a0be8 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007ffe192a0bf0 RCX: 00007fcfd760b6d9
RDX: 0000000000000010 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007ffe192a0bf8 R08: 6c616b7a79732f2e R09: 6c616b7a79732f2e
R10: 6c616b7a79732f2e R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe192a0e58 R14: 0000000000000001 R15: 0000000000000001
</TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x56388aa96 pfn:0x7fc17
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001ffe808 ffff8880b8644af0 0000000000000000
raw: 000000056388aa96 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 5214, tgid 5214 (sftp-server), ts 74824128125, free_ts 74900105933
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1537
prep_new_page mm/page_alloc.c:1545 [inline]
get_page_from_freelist+0x3039/0x3180 mm/page_alloc.c:3457
__alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4733
alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
folio_alloc_mpol_noprof mm/mempolicy.c:2283 [inline]
vma_alloc_folio_noprof+0x12e/0x230 mm/mempolicy.c:2314
folio_prealloc+0x31/0x170
alloc_anon_folio mm/memory.c:4721 [inline]
do_anonymous_page mm/memory.c:4778 [inline]
do_pte_missing mm/memory.c:3963 [inline]
handle_pte_fault+0x24dd/0x6800 mm/memory.c:5751
__handle_mm_fault mm/memory.c:5894 [inline]
handle_mm_fault+0x1053/0x1ad0 mm/memory.c:6062
do_user_addr_fault arch/x86/mm/fault.c:1338 [inline]
handle_page_fault arch/x86/mm/fault.c:1481 [inline]
exc_page_fault+0x459/0x8c0 arch/x86/mm/fault.c:1539
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5214 tgid 5214 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1108 [inline]
free_unref_folios+0xee2/0x18a0 mm/page_alloc.c:2686
folios_put_refs+0x76c/0x860 mm/swap.c:1007
free_pages_and_swap_cache+0x2ea/0x690 mm/swap_state.c:332
__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+0x496/0xc40 mm/mmap.c:1877
__mmput+0x115/0x380 kernel/fork.c:1347
exit_mm+0x220/0x310 kernel/exit.c:571
do_exit+0x9b2/0x28e0 kernel/exit.c:926
do_group_exit+0x207/0x2c0 kernel/exit.c:1088
__do_sys_exit_group kernel/exit.c:1099 [inline]
__se_sys_exit_group kernel/exit.c:1097 [inline]
__x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1097
x64_sys_call+0x2634/0x2640 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff88807fc16f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88807fc16f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88807fc17000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88807fc17080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88807fc17100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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