[Android 5.15] KASAN: use-after-free Read in ext4_xattr_ibody_get

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8969ee93a483 Merge android13-5.15 into android13-5.15-lts
git tree: android13-5.15-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=15086eb6580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3ef8af16142b9dd4
dashboard link: https://syzkaller.appspot.com/bug?extid=51dbb0b06cc568475c91
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=121803ec580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15f4232e580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d686db73bf84/disk-8969ee93.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6253ebf315ec/vmlinux-8969ee93.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a673b5918e79/bzImage-8969ee93.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/712b781427fc/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=141803ec580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+51dbb0...@syzkaller.appspotmail.com

EXT4-fs (loop2): mounted filesystem without journal. Opts: block_validity,bsddf,nombcache,inode_readahead_blks=0x0000000000000000,debug_want_extra_isize=0x0000000000000080,orlov,nogrpid,noauto_da_alloc,grpjquota=,,errors=continue. Quota mode: none.
==================================================================
BUG: KASAN: use-after-free in xattr_find_entry fs/ext4/xattr.c:294 [inline]
BUG: KASAN: use-after-free in ext4_xattr_ibody_get+0x62e/0x690 fs/ext4/xattr.c:601
Read of size 4 at addr ffff88810c8dc004 by task syz.2.18/375

CPU: 0 PID: 375 Comm: syz.2.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<TASK>
__dump_stack+0x21/0x30 lib/dump_stack.c:88
dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:427 [inline]
kasan_report+0xf1/0x140 mm/kasan/report.c:444
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
xattr_find_entry fs/ext4/xattr.c:294 [inline]
ext4_xattr_ibody_get+0x62e/0x690 fs/ext4/xattr.c:601
ext4_xattr_get+0x116/0x820 fs/ext4/xattr.c:655
ext4_get_acl+0x85/0x670 fs/ext4/acl.c:165
get_acl+0x161/0x270 fs/posix_acl.c:153
posix_acl_chmod+0xe9/0x250 fs/posix_acl.c:602
ext4_setattr+0xb23/0x1ac0 fs/ext4/inode.c:5672
notify_change+0xbca/0xe90 fs/attr.c:505
chmod_common+0x223/0x3c0 fs/open.c:583
do_fchmodat+0xd4/0x1a0 fs/open.c:622
__do_sys_fchmodat fs/open.c:635 [inline]
__se_sys_fchmodat fs/open.c:632 [inline]
__x64_sys_fchmodat+0x7b/0x90 fs/open.c:632
x64_sys_call+0x1b7/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:269
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fcc16012e59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe12da6208 EFLAGS: 00000246 ORIG_RAX: 000000000000010c
RAX: ffffffffffffffda RBX: 00007fcc1628bfa0 RCX: 00007fcc16012e59
RDX: 000000000000017f RSI: 0000200000000300 RDI: ffffffffffffff9c
RBP: 00007fcc160a8d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcc1628bfac R14: 00007fcc1628bfa0 R15: 00007fcc1628bfa0
</TASK>

The buggy address belongs to the page:
page:ffffea0004323700 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10c8dc
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004323748 ffffea0004b2ee48 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x500dc0(GFP_USER|__GFP_ZERO|__GFP_ACCOUNT), pid 323, ts 25773759575, free_ts 25780491821
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605
prep_new_page+0x1c/0x110 mm/page_alloc.c:2611
get_page_from_freelist+0x2d3a/0x2dc0 mm/page_alloc.c:4485
__alloc_pages+0x1a2/0x460 mm/page_alloc.c:5822
__alloc_pages_node include/linux/gfp.h:595 [inline]
alloc_pages_node include/linux/gfp.h:609 [inline]
alloc_pages include/linux/gfp.h:622 [inline]
__pte_alloc_one include/asm-generic/pgalloc.h:63 [inline]
pte_alloc_one+0x70/0x190 arch/x86/mm/pgtable.c:33
__pte_alloc+0x75/0x2a0 mm/memory.c:504
copy_pte_range mm/memory.c:1098 [inline]
copy_pmd_range mm/memory.c:1233 [inline]
copy_pud_range mm/memory.c:1270 [inline]
copy_p4d_range mm/memory.c:1294 [inline]
copy_page_range+0x237c/0x28d0 mm/memory.c:1367
dup_mmap kernel/fork.c:663 [inline]
dup_mm kernel/fork.c:1527 [inline]
copy_mm+0xbf2/0x13c0 kernel/fork.c:1579
copy_process+0x117c/0x3250 kernel/fork.c:2353
kernel_clone+0x233/0x960 kernel/fork.c:2742
__do_sys_clone kernel/fork.c:2868 [inline]
__se_sys_clone kernel/fork.c:2852 [inline]
__x64_sys_clone+0x198/0x210 kernel/fork.c:2852
x64_sys_call+0x41f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:57
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
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+0x542/0x550 mm/page_alloc.c:3534
free_unref_page_list+0x13a/0x9d0 mm/page_alloc.c:3671
release_pages+0x1279/0x12e0 mm/swap.c:1015
free_pages_and_swap_cache+0x86/0xa0 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+0x17e/0x310 mm/mmu_gather.c:338
exit_mmap+0x43b/0x8b0 mm/mmap.c:3248
__mmput+0x93/0x320 kernel/fork.c:1185
mmput+0x50/0x150 kernel/fork.c:1208
exit_mm kernel/exit.c:555 [inline]
do_exit+0xa89/0x2890 kernel/exit.c:877
do_group_exit+0x141/0x310 kernel/exit.c:1004
get_signal+0x66a/0x1480 kernel/signal.c:2907
arch_do_signal_or_restart+0xdf/0x11c0 arch/x86/kernel/signal.c:867
handle_signal_work kernel/entry/common.c:154 [inline]
exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178
exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86

Memory state around the buggy address:
ffff88810c8dbf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88810c8dbf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88810c8dc000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88810c8dc080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88810c8dc100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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