[syzbot ci] Re: mm/madvise: prefer VMA lock for MADV_REMOVE
From: syzbot ci
Date: Wed Jan 14 2026 - 03:03:11 EST
syzbot ci has tested the following series
[v1] mm/madvise: prefer VMA lock for MADV_REMOVE
https://lore.kernel.org/all/202601141124178748cM66DJW2fzNea7Uym1mG@xxxxxxxxxx
* [PATCH linux-next] mm/madvise: prefer VMA lock for MADV_REMOVE
and found the following issue:
possible deadlock in blkdev_fallocate
Full report is available here:
https://ci.syzbot.org/series/30acb9df-ca55-4cbf-81ed-89b84da8edc1
***
possible deadlock in blkdev_fallocate
tree: linux-next
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next
base: 4c81c9dc03a068745eeb56984ea9836d86fa3eb2
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/eaa5a44b-5d87-4428-b098-72b46efdb983/config
C repro: https://ci.syzbot.org/findings/e3240f02-6d2c-4c6d-bc6e-e7f4be22e433/c_repro
syz repro: https://ci.syzbot.org/findings/e3240f02-6d2c-4c6d-bc6e-e7f4be22e433/syz_repro
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.17/5976 is trying to acquire lock:
ffff888167a287a8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: inode_lock include/linux/fs.h:1027 [inline]
ffff888167a287a8 (&sb->s_type->i_mutex_key#10){++++}-{4:4}, at: blkdev_fallocate+0x260/0x530 block/fops.c:908
but task is already holding lock:
ffff8881043c3b88 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x1d1/0x500 mm/mmap_lock.c:259
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (vm_lock){++++}-{0:0}:
__vma_enter_locked+0x243/0x710 mm/mmap_lock.c:72
__vma_start_write+0x23/0x140 mm/mmap_lock.c:104
vma_start_write include/linux/mmap_lock.h:213 [inline]
mprotect_fixup+0x5e1/0xa50 mm/mprotect.c:768
setup_arg_pages+0x565/0xae0 fs/exec.c:670
load_elf_binary+0xc5e/0x2980 fs/binfmt_elf.c:1028
search_binary_handler fs/exec.c:1669 [inline]
exec_binprm fs/exec.c:1701 [inline]
bprm_execve+0x93d/0x1410 fs/exec.c:1753
kernel_execve+0x8ef/0x9e0 fs/exec.c:1919
try_to_run_init_process+0x13/0x60 init/main.c:1506
kernel_init+0xad/0x1d0 init/main.c:1634
ret_from_fork+0x51b/0xa40 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
-> #1 (&mm->mmap_lock){++++}-{4:4}:
__might_fault+0xcb/0x130 mm/memory.c:7174
_copy_to_iter+0xf9/0x17d0 lib/iov_iter.c:196
copy_page_to_iter+0x10c/0x1c0 lib/iov_iter.c:374
copy_folio_to_iter include/linux/uio.h:204 [inline]
filemap_read+0x811/0x1230 mm/filemap.c:2851
blkdev_read_iter+0x30a/0x440 block/fops.c:856
new_sync_read fs/read_write.c:491 [inline]
vfs_read+0x582/0xa70 fs/read_write.c:572
ksys_read+0x150/0x270 fs/read_write.c:715
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (&sb->s_type->i_mutex_key#10){++++}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x106/0x330 kernel/locking/lockdep.c:5868
down_write+0x96/0x200 kernel/locking/rwsem.c:1590
inode_lock include/linux/fs.h:1027 [inline]
blkdev_fallocate+0x260/0x530 block/fops.c:908
vfs_fallocate+0x669/0x7e0 fs/open.c:339
madvise_remove mm/madvise.c:1055 [inline]
madvise_vma_behavior+0x120d/0x4460 mm/madvise.c:1379
madvise_walk_vmas+0x90e/0xaf0 mm/madvise.c:1706
madvise_do_behavior+0x386/0x540 mm/madvise.c:1956
do_madvise+0x1fa/0x2e0 mm/madvise.c:2049
__do_sys_madvise mm/madvise.c:2058 [inline]
__se_sys_madvise mm/madvise.c:2056 [inline]
__x64_sys_madvise+0xa6/0xc0 mm/madvise.c:2056
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Chain exists of:
&sb->s_type->i_mutex_key#10 --> &mm->mmap_lock --> vm_lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(vm_lock);
lock(&mm->mmap_lock);
lock(vm_lock);
lock(&sb->s_type->i_mutex_key#10);
*** DEADLOCK ***
1 lock held by syz.0.17/5976:
#0: ffff8881043c3b88 (vm_lock){++++}-{0:0}, at: lock_vma_under_rcu+0x1d1/0x500 mm/mmap_lock.c:259
stack backtrace:
CPU: 1 UID: 0 PID: 5976 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x106/0x330 kernel/locking/lockdep.c:5868
down_write+0x96/0x200 kernel/locking/rwsem.c:1590
inode_lock include/linux/fs.h:1027 [inline]
blkdev_fallocate+0x260/0x530 block/fops.c:908
vfs_fallocate+0x669/0x7e0 fs/open.c:339
madvise_remove mm/madvise.c:1055 [inline]
madvise_vma_behavior+0x120d/0x4460 mm/madvise.c:1379
madvise_walk_vmas+0x90e/0xaf0 mm/madvise.c:1706
madvise_do_behavior+0x386/0x540 mm/madvise.c:1956
do_madvise+0x1fa/0x2e0 mm/madvise.c:2049
__do_sys_madvise mm/madvise.c:2058 [inline]
__se_sys_madvise mm/madvise.c:2056 [inline]
__x64_sys_madvise+0xa6/0xc0 mm/madvise.c:2056
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5ceb59acb9
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:00007ffd12a05518 EFLAGS: 00000246 ORIG_RAX: 000000000000001c
RAX: ffffffffffffffda RBX: 00007f5ceb815fa0 RCX: 00007f5ceb59acb9
RDX: 0000000000000009 RSI: 0000000000004000 RDI: 0000200000119000
RBP: 00007f5ceb608bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5ceb815fac R14: 00007f5ceb815fa0 R15: 00007f5ceb815fa0
</TASK>
***
If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syzbot@xxxxxxxxxxxxxxxxxxxxxxxxx
---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.