Re: [syzbot] [mm?] possible deadlock in shmem_file_write_iter

From: syzbot
Date: Sun Sep 29 2024 - 12:46:38 EST

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syzbot has found a reproducer for the following issue on:

HEAD commit: 3efc57369a0c Merge tag 'for-linus' of git://git.kernel.org..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1648f507980000
kernel config: https://syzkaller.appspot.com/x/.config?x=a4fcb065287cdb84
dashboard link: https://syzkaller.appspot.com/bug?extid=288aa6838b3263f52e7e
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=17af2980580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11607d9f980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b5a4faec7a99/disk-3efc5736.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/971adf9a5295/vmlinux-3efc5736.xz
kernel image: https://storage.googleapis.com/syzbot-assets/49516da34e16/bzImage-3efc5736.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+288aa6838b3263f52e7e@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.11.0-syzkaller-11993-g3efc57369a0c #0 Not tainted
------------------------------------------------------
syz-executor601/5480 is trying to acquire lock:
ffff888021316098 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:153

but task is already holding lock:
ffff8880120b02c8 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:815 [inline]
ffff8880120b02c8 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: shmem_file_write_iter+0x80/0x120 mm/shmem.c:3211

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
down_write+0x99/0x220 kernel/locking/rwsem.c:1579
inode_lock include/linux/fs.h:815 [inline]
process_measurement+0x439/0x1fb0 security/integrity/ima/ima_main.c:250
ima_file_mmap+0x13d/0x2b0 security/integrity/ima/ima_main.c:455
security_mmap_file+0x7e7/0xa40 security/security.c:2977
__do_sys_remap_file_pages mm/mmap.c:1692 [inline]
__se_sys_remap_file_pages+0x6e6/0xa50 mm/mmap.c:1624
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

-> #0 (&mm->mmap_lock){++++}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3158 [inline]
check_prevs_add kernel/locking/lockdep.c:3277 [inline]
validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3901
__lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5199
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
down_read_killable+0xca/0xd30 kernel/locking/rwsem.c:1549
mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:153
get_mmap_lock_carefully mm/memory.c:6108 [inline]
lock_mm_and_find_vma+0x29c/0x2f0 mm/memory.c:6159
do_user_addr_fault arch/x86/mm/fault.c:1361 [inline]
handle_page_fault arch/x86/mm/fault.c:1481 [inline]
exc_page_fault+0x1bf/0x8c0 arch/x86/mm/fault.c:1539
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
fault_in_readable+0x165/0x2b0
fault_in_iov_iter_readable+0x229/0x280 lib/iov_iter.c:94
generic_perform_write+0x259/0x6d0 mm/filemap.c:4044
shmem_file_write_iter+0xf9/0x120 mm/shmem.c:3221
new_sync_write fs/read_write.c:590 [inline]
vfs_write+0xa6d/0xc90 fs/read_write.c:683
ksys_write+0x183/0x2b0 fs/read_write.c:736
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

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#12);
lock(&mm->mmap_lock);
lock(&sb->s_type->i_mutex_key#12);
rlock(&mm->mmap_lock);

*** DEADLOCK ***

3 locks held by syz-executor601/5480:
#0: ffff888028a922b8 (&f->f_pos_lock){+.+.}-{3:3}, at: fdget_pos+0x24e/0x320 fs/file.c:1187
#1: ffff888076168420 (sb_writers#5){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2931 [inline]
#1: ffff888076168420 (sb_writers#5){.+.+}-{0:0}, at: vfs_write+0x224/0xc90 fs/read_write.c:679
#2: ffff8880120b02c8 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:815 [inline]
#2: ffff8880120b02c8 (&sb->s_type->i_mutex_key#12){+.+.}-{3:3}, at: shmem_file_write_iter+0x80/0x120 mm/shmem.c:3211

stack backtrace:
CPU: 1 UID: 0 PID: 5480 Comm: syz-executor601 Not tainted 6.11.0-syzkaller-11993-g3efc57369a0c #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_circular_bug+0x13a/0x1b0 kernel/locking/lockdep.c:2074
check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2203
check_prev_add kernel/locking/lockdep.c:3158 [inline]
check_prevs_add kernel/locking/lockdep.c:3277 [inline]
validate_chain+0x18ef/0x5920 kernel/locking/lockdep.c:3901
__lock_acquire+0x1384/0x2050 kernel/locking/lockdep.c:5199
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5822
down_read_killable+0xca/0xd30 kernel/locking/rwsem.c:1549
mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:153
get_mmap_lock_carefully mm/memory.c:6108 [inline]
lock_mm_and_find_vma+0x29c/0x2f0 mm/memory.c:6159
do_user_addr_fault arch/x86/mm/fault.c:1361 [inline]
handle_page_fault arch/x86/mm/fault.c:1481 [inline]
exc_page_fault+0x1bf/0x8c0 arch/x86/mm/fault.c:1539
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0010:fault_in_readable+0x165/0x2b0 mm/gup.c:2235
Code: b3 ff 4c 8d b3 ff 0f 00 00 48 89 d8 4d 01 e6 49 81 e6 00 f0 ff ff 49 39 c6 72 6b e8 b5 c8 b3 ff 4c 39 f3 74 6e 4c 89 64 24 10 <44> 8a 23 43 0f b6 04 2f 84 c0 75 18 44 88 64 24 40 48 81 c3 00 10
RSP: 0018:ffffc900041e7a40 EFLAGS: 00050293
RAX: ffffffff81e11d97 RBX: 00000000200ee000 RCX: ffff888024029e00
RDX: 0000000000000000 RSI: 0000000000000240 RDI: 0000000000000000
RBP: ffffc900041e7af8 R08: ffffffff81e11d08 R09: ffffffff84b941b9
R10: 0000000000000002 R11: ffff888024029e00 R12: 0000000000200000
R13: dffffc0000000000 R14: 0000000020201000 R15: 1ffff9200083cf50
fault_in_iov_iter_readable+0x229/0x280 lib/iov_iter.c:94
generic_perform_write+0x259/0x6d0 mm/filemap.c:4044
shmem_file_write_iter+0xf9/0x120 mm/shmem.c:3221
new_sync_write fs/read_write.c:590 [inline]
vfs_write+0xa6d/0xc90 fs/read_write.c:683
ksys_write+0x183/0x2b0 fs/read_write.c:736
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: 0033:0x7fd0953e3829
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 18 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd09537c238 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd09546e3d8 RCX: 00007fd0953e3829
RDX: 000000000208e24b RSI: 0000000020000240 RDI: 0000000000000003
RBP: 00007fd09546e3d0 R08: 00007fd09537c6c0 R09: 00007fd09537c6c0
R10: 00007fd09537c6c0 R11: 0000000000000246 R12: 00007fd09546e3dc
R13: 000000000000006e R14: 00007ffc57bc6200 R15: 00007ffc57bc62e8
</TASK>
----------------
Code disassembly (best guess):
0: b3 ff mov $0xff,%bl
2: 4c 8d b3 ff 0f 00 00 lea 0xfff(%rbx),%r14
9: 48 89 d8 mov %rbx,%rax
c: 4d 01 e6 add %r12,%r14
f: 49 81 e6 00 f0 ff ff and $0xfffffffffffff000,%r14
16: 49 39 c6 cmp %rax,%r14
19: 72 6b jb 0x86
1b: e8 b5 c8 b3 ff call 0xffb3c8d5
20: 4c 39 f3 cmp %r14,%rbx
23: 74 6e je 0x93
25: 4c 89 64 24 10 mov %r12,0x10(%rsp)
* 2a: 44 8a 23 mov (%rbx),%r12b <-- trapping instruction
2d: 43 0f b6 04 2f movzbl (%r15,%r13,1),%eax
32: 84 c0 test %al,%al
34: 75 18 jne 0x4e
36: 44 88 64 24 40 mov %r12b,0x40(%rsp)
3b: 48 rex.W
3c: 81 .byte 0x81
3d: c3 ret
3e: 00 10 add %dl,(%rax)

---
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#syz test: git://repo/address.git branch-or-commit-hash
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Next message: Jonathan Cameron: "Re: [PATCH] iio: adc: mt6360-adc: Converted to use get_unaligned_be16()"
Previous message: Oleg Nesterov: "[PATCH v2] uprobes: fix kernel info leak via "[uprobes]" vma"
In reply to: syzbot: "[syzbot] [mm?] possible deadlock in shmem_file_write_iter"
Next in thread: syzbot: "Re: [syzbot] [mm?] possible deadlock in shmem_file_write_iter"
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