From: syzbot <syzbot+b72767277f29b6407083@syzkaller.appspotmail.com>
To: davem@davemloft.net, edumazet@google.com, horms@kernel.org,
kuba@kernel.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, pabeni@redhat.com,
syzkaller-bugs@googlegroups.com
Subject: [syzbot] [net?] KASAN: use-after-free Read in filemap_map_pages
Date: Mon, 01 Jun 2026 04:47:26 -0700 [thread overview]
Message-ID: <6a1d714e.c1435f33.295d1e.2a35.GAE@google.com> (raw)
Hello,
syzbot found the following issue on:
HEAD commit: d60ec36cab33 Merge tag 'mm-hotfixes-stable-2026-05-25-16-2..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=124501ec580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8d24a1331e060dda
dashboard link: https://syzkaller.appspot.com/bug?extid=b72767277f29b6407083
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: i386
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/864236422e21/disk-d60ec36c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/858219f0a900/vmlinux-d60ec36c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/809d091c238e/bzImage-d60ec36c.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b72767277f29b6407083@syzkaller.appspotmail.com
==================================================================
BUG: KASAN: use-after-free in ptep_get include/linux/pgtable.h:461 [inline]
BUG: KASAN: use-after-free in filemap_map_order0_folio mm/filemap.c:3856 [inline]
BUG: KASAN: use-after-free in filemap_map_pages+0xc7a/0x2100 mm/filemap.c:3932
Read of size 8 at addr ffff88807bed6d50 by task syz.1.7707/30545
CPU: 1 UID: 0 PID: 30545 Comm: syz.1.7707 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_address_description+0x55/0x1e0 mm/kasan/report.c:378
print_report+0x58/0x70 mm/kasan/report.c:482
kasan_report+0x117/0x150 mm/kasan/report.c:595
ptep_get include/linux/pgtable.h:461 [inline]
filemap_map_order0_folio mm/filemap.c:3856 [inline]
filemap_map_pages+0xc7a/0x2100 mm/filemap.c:3932
do_fault_around mm/memory.c:5867 [inline]
do_read_fault mm/memory.c:5900 [inline]
do_fault mm/memory.c:6043 [inline]
do_pte_missing+0x1f38/0x33f0 mm/memory.c:4566
handle_pte_fault mm/memory.c:6427 [inline]
__handle_mm_fault mm/memory.c:6565 [inline]
handle_mm_fault+0x1bf2/0x3170 mm/memory.c:6734
do_user_addr_fault+0x75b/0x1340 arch/x86/mm/fault.c:1385
handle_page_fault arch/x86/mm/fault.c:1474 [inline]
exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0010:rep_movs_alternative+0x30/0x90 arch/x86/lib/copy_user_64.S:60
Code: 83 f9 08 73 25 85 c9 74 0f 8a 06 88 07 48 ff c7 48 ff c6 48 ff c9 75 f1 c3 cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 <48> 8b 06 48 89 07 48 83 c6 08 48 83 c7 08 83 e9 08 74 db 83 f9 08
RSP: 0000:ffffc9000cb978b8 EFLAGS: 00050206
RAX: 00007ffffffff001 RBX: 000000000000001c RCX: 000000000000001c
RDX: 0000000000000001 RSI: 00000000800bcae0 RDI: ffffc9000cb97940
RBP: ffffc9000cb979d0 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52001972f2b R12: dffffc0000000000
R13: ffffc9000cb97c80 R14: ffffc9000cb97940 R15: 00000000800bcae0
copy_user_generic arch/x86/include/asm/uaccess_64.h:126 [inline]
raw_copy_from_user arch/x86/include/asm/uaccess_64.h:141 [inline]
_inline_copy_from_user include/linux/uaccess.h:185 [inline]
_copy_from_user+0x7a/0xb0 lib/usercopy.c:18
copy_from_user include/linux/uaccess.h:223 [inline]
get_compat_msghdr+0xb3/0x4c0 net/compat.c:91
recvmsg_copy_msghdr net/socket.c:2882 [inline]
___sys_recvmsg+0x1dd/0x590 net/socket.c:2956
do_recvmmsg+0x3a5/0x800 net/socket.c:3047
__sys_recvmmsg+0x1a5/0x290 net/socket.c:3129
__do_compat_sys_recvmmsg_time32 net/compat.c:418 [inline]
__se_compat_sys_recvmmsg_time32 net/compat.c:414 [inline]
__ia32_compat_sys_recvmmsg_time32+0xbf/0xe0 net/compat.c:414
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0x229/0x6e0 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7fa501c
Code: 90 85 d2 74 0a 89 ce 81 e6 ff 0f 00 00 89 32 85 c0 74 05 c1 e9 0c 89 08 31 c0 5e 5d c3 90 0f 1f 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 58 b8
RSP: 002b:00000000f544550c EFLAGS: 00000206 ORIG_RAX: 0000000000000151
RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 00000000800000c0
RDX: 0000000000010106 RSI: 0000000000000002 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x121f pfn:0x7bed6
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f0(buddy)
raw: 00fff00000000000 ffffea0000fea188 ffffea0002346808 0000000000000000
raw: 000000000000121f 0000000000000000 00000000f0000000 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 0x140cc2(GFP_HIGHUSER|__GFP_COMP), pid 29415, tgid 29414 (syz.1.7355), ts 1634224509357, free_ts 1634614223058
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x22d/0x280 mm/page_alloc.c:1853
prep_new_page mm/page_alloc.c:1861 [inline]
get_page_from_freelist+0x2593/0x2610 mm/page_alloc.c:3941
__alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5221
alloc_pages_mpol+0x235/0x490 mm/mempolicy.c:2490
alloc_frozen_pages_noprof mm/mempolicy.c:2561 [inline]
alloc_pages_noprof+0xac/0x2a0 mm/mempolicy.c:2581
folio_alloc_noprof+0x1e/0x30 mm/mempolicy.c:2591
filemap_alloc_folio_noprof+0x111/0x470 mm/filemap.c:1014
filemap_create_folio mm/filemap.c:2612 [inline]
filemap_get_pages+0x819/0x1ef0 mm/filemap.c:2702
filemap_read+0x447/0x1230 mm/filemap.c:2806
__kernel_read+0x504/0x9b0 fs/read_write.c:532
integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
ima_calc_file_hash+0x446/0x860 security/integrity/ima/ima_crypto.c:280
ima_collect_measurement+0x51d/0x9c0 security/integrity/ima/ima_api.c:300
process_measurement+0x12cd/0x1c80 security/integrity/ima/ima_main.c:425
ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:685
security_file_post_open+0xb3/0x260 security/security.c:2755
page last free pid 29415 tgid 29414 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1397 [inline]
free_unref_folios+0xd9f/0x14c0 mm/page_alloc.c:2999
folios_put_refs+0x9ff/0xb40 mm/swap.c:1008
folio_batch_release include/linux/folio_batch.h:101 [inline]
truncate_inode_pages_range+0x3dd/0xe30 mm/truncate.c:408
evict+0x631/0xb10 fs/inode.c:843
__dentry_kill+0x1a2/0x690 fs/dcache.c:718
shrink_kill+0xa9/0x2c0 fs/dcache.c:1195
shrink_dentry_list+0x2e0/0x5e0 fs/dcache.c:1222
shrink_dcache_tree+0xe9/0x5d0 fs/dcache.c:-1
do_one_tree fs/dcache.c:1721 [inline]
shrink_dcache_for_umount+0xa8/0x1f0 fs/dcache.c:1738
generic_shutdown_super+0x6f/0x2d0 fs/super.c:624
kill_anon_super+0x3b/0x70 fs/super.c:1292
deactivate_locked_super+0xbc/0x130 fs/super.c:476
cleanup_mnt+0x437/0x4d0 fs/namespace.c:1312
task_work_run+0x1d9/0x270 kernel/task_work.c:233
exit_task_work include/linux/task_work.h:40 [inline]
do_exit+0x70f/0x22c0 kernel/exit.c:976
do_group_exit+0x21b/0x2d0 kernel/exit.c:1119
Memory state around the buggy address:
ffff88807bed6c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88807bed6c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88807bed6d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88807bed6d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88807bed6e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
----------------
Code disassembly (best guess):
0: 83 f9 08 cmp $0x8,%ecx
3: 73 25 jae 0x2a
5: 85 c9 test %ecx,%ecx
7: 74 0f je 0x18
9: 8a 06 mov (%rsi),%al
b: 88 07 mov %al,(%rdi)
d: 48 ff c7 inc %rdi
10: 48 ff c6 inc %rsi
13: 48 ff c9 dec %rcx
16: 75 f1 jne 0x9
18: c3 ret
19: cc int3
1a: cc int3
1b: cc int3
1c: cc int3
1d: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
24: 00 00 00
27: 0f 1f 00 nopl (%rax)
* 2a: 48 8b 06 mov (%rsi),%rax <-- trapping instruction
2d: 48 89 07 mov %rax,(%rdi)
30: 48 83 c6 08 add $0x8,%rsi
34: 48 83 c7 08 add $0x8,%rdi
38: 83 e9 08 sub $0x8,%ecx
3b: 74 db je 0x18
3d: 83 f9 08 cmp $0x8,%ecx
---
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reply other threads:[~2026-06-01 11:47 UTC|newest]
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