[Android 6.1] KASAN: use-after-free Read in ext4_xattr_list_entries

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e69716042404 UPSTREAM: eventpoll: fix ep_remove struct eve..
git tree: android14-6.1
console output: https://syzkaller.appspot.com/x/log.txt?x=11b5fb89580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6af0777879025b2
dashboard link: https://syzkaller.appspot.com/bug?extid=e9c2cc0e1e674e43ef5a
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=177a98b9580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15b5fb89580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/69c131ba90c8/disk-e6971604.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/68ea5a8a2699/vmlinux-e6971604.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5d18831fb25d/bzImage-e6971604.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/9b20f637cdaf/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=11780c32580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e9c2cc...@syzkaller.appspotmail.com

EXT4-fs: Ignoring removed oldalloc option
EXT4-fs: Ignoring removed mblk_io_submit option
EXT4-fs (loop2): encrypted files will use data=ordered instead of data journaling mode
EXT4-fs (loop2): 1 truncate cleaned up
EXT4-fs (loop2): mounted filesystem without journal. Quota mode: none.
==================================================================
BUG: KASAN: out-of-bounds in ext4_xattr_list_entries+0x2d8/0x380 fs/ext4/xattr.c:670
Read of size 4 at addr ffff88813052c018 by task syz.2.18/380

CPU: 1 PID: 380 Comm: syz.2.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Call Trace:
<TASK>
__dump_stack+0x21/0x24 lib/dump_stack.c:88
dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
print_address_description+0x71/0x200 mm/kasan/report.c:316
print_report+0x4a/0x60 mm/kasan/report.c:420
kasan_report+0x122/0x150 mm/kasan/report.c:524
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
ext4_xattr_list_entries+0x2d8/0x380 fs/ext4/xattr.c:670
ext4_xattr_ibody_list fs/ext4/xattr.c:740 [inline]
ext4_listxattr+0x20e/0x600 fs/ext4/xattr.c:765
vfs_listxattr fs/xattr.c:457 [inline]
listxattr+0x2a8/0x310 fs/xattr.c:804
path_listxattr+0xe1/0x1b0 fs/xattr.c:828
__do_sys_listxattr fs/xattr.c:840 [inline]
__se_sys_listxattr fs/xattr.c:837 [inline]
__x64_sys_listxattr+0x80/0x90 fs/xattr.c:837
x64_sys_call+0xd7/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:195
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fce81f9de59
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:00007ffe8b8fc4e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000c2
RAX: ffffffffffffffda RBX: 00007fce82225fa0 RCX: 00007fce81f9de59
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000200000000140
RBP: 00007fce82033e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fce82225fac R14: 00007fce82225fa0 R15: 00007fce82225fa0
</TASK>

The buggy address belongs to the physical page:
page:ffffea0004c14b00 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x13052c
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004c14b48 ffffea0004c14a88 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 311, tgid 311 (udevd), ts 28584793787, free_ts 28588351102
set_page_owner include/linux/page_owner.h:33 [inline]
post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2672
prep_new_page+0x1c/0x110 mm/page_alloc.c:2679
get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4586
__alloc_pages+0x1fa/0x610 mm/page_alloc.c:5930
__folio_alloc+0x12/0x40 mm/page_alloc.c:5963
__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:4286 [inline]
handle_pte_fault mm/memory.c:5181 [inline]
__handle_mm_fault mm/memory.c:5325 [inline]
handle_mm_fault+0x1989/0x26b0 mm/memory.c:5465
do_user_addr_fault+0x61e/0x1030 arch/x86/mm/fault.c:1372
handle_page_fault arch/x86/mm/fault.c:1464 [inline]
exc_page_fault+0x51/0xb0 arch/x86/mm/fault.c:1517
asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:608
page last free stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
free_pages_prepare mm/page_alloc.c:1580 [inline]
free_pcp_prepare mm/page_alloc.c:1654 [inline]
free_unref_page_prepare+0x80c/0x820 mm/page_alloc.c:3621
free_unref_page_list+0x117/0x8d0 mm/page_alloc.c:3772
release_pages+0xc7e/0xce0 mm/swap.c:1053
free_pages_and_swap_cache+0x86/0xa0 mm/swap_state.c:316
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+0x1b2/0x380 mm/mmu_gather.c:361
unmap_region+0x2b7/0x320 mm/mmap.c:2419
do_mas_align_munmap+0xbf3/0x1330 mm/mmap.c:2693
do_mas_munmap+0x23d/0x2b0 mm/mmap.c:2751
__vm_munmap+0x1af/0x310 mm/mmap.c:3050
__do_sys_munmap mm/mmap.c:3076 [inline]
__se_sys_munmap mm/mmap.c:3072 [inline]
__x64_sys_munmap+0x6b/0x80 mm/mmap.c:3072
x64_sys_call+0x8a/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:12
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Memory state around the buggy address:
ffff88813052bf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88813052bf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88813052c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88813052c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88813052c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


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