[syzbot] [mm?] possible deadlock in gup_fast_fallback

From: syzbot
Date: Sat Apr 20 2024 - 23:14:30 EST

Hello,

syzbot found the following issue on:

HEAD commit: 66e4190e92ce Add linux-next specific files for 20240416
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1526f44f180000
kernel config: https://syzkaller.appspot.com/x/.config?x=c247afaa437e6409
dashboard link: https://syzkaller.appspot.com/bug?extid=63ba90b81c16b86379bd
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/86891dae5f9c/disk-66e4190e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1ca383660bf2/vmlinux-66e4190e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bf6ff37d3fcc/bzImage-66e4190e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+63ba90b81c16b86379bd@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc4-next-20240416-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.2/9254 is trying to acquire lock:
ffff88802c2f0b18 (&mm->mmap_lock){++++}-{3:3}, at: gup_fast_fallback+0x233/0x2b40 mm/gup.c:3442

but task is already holding lock:
ffff88806a3c3d80 (&sb->s_type->i_mutex_key#29){++++}-{3:3}, at: inode_lock include/linux/fs.h:791 [inline]
ffff88806a3c3d80 (&sb->s_type->i_mutex_key#29){++++}-{3:3}, at: __blockdev_direct_IO+0x346/0x49b0 fs/direct-io.c:1146

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&sb->s_type->i_mutex_key#29){++++}-{3:3}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
down_write+0x3a/0x50 kernel/locking/rwsem.c:1579
inode_lock include/linux/fs.h:791 [inline]
exfat_page_mkwrite+0x43a/0xea0 fs/exfat/file.c:629
do_page_mkwrite+0x19b/0x480 mm/memory.c:3097
do_shared_fault mm/memory.c:4977 [inline]
do_fault mm/memory.c:5039 [inline]
do_pte_missing mm/memory.c:3881 [inline]
handle_pte_fault+0x1298/0x6dc0 mm/memory.c:5359
__handle_mm_fault mm/memory.c:5500 [inline]
handle_mm_fault+0x10e7/0x1bb0 mm/memory.c:5665
do_user_addr_fault arch/x86/mm/fault.c:1420 [inline]
handle_page_fault arch/x86/mm/fault.c:1512 [inline]
exc_page_fault+0x2b9/0x900 arch/x86/mm/fault.c:1570
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

-> #1 (sb_pagefaults#3){.+.+}-{0:0}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1659 [inline]
sb_start_pagefault include/linux/fs.h:1824 [inline]
exfat_page_mkwrite+0x161/0xea0 fs/exfat/file.c:619
do_page_mkwrite+0x19b/0x480 mm/memory.c:3097
do_shared_fault mm/memory.c:4977 [inline]
do_fault mm/memory.c:5039 [inline]
do_pte_missing mm/memory.c:3881 [inline]
handle_pte_fault+0x1298/0x6dc0 mm/memory.c:5359
__handle_mm_fault mm/memory.c:5500 [inline]
handle_mm_fault+0x10e7/0x1bb0 mm/memory.c:5665
do_user_addr_fault arch/x86/mm/fault.c:1420 [inline]
handle_page_fault arch/x86/mm/fault.c:1512 [inline]
exc_page_fault+0x2b9/0x900 arch/x86/mm/fault.c:1570
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

-> #0 (&mm->mmap_lock){++++}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
gup_fast_fallback+0x24c/0x2b40 mm/gup.c:3442
pin_user_pages_fast+0xcc/0x160 mm/gup.c:3566
iov_iter_extract_user_pages lib/iov_iter.c:1583 [inline]
iov_iter_extract_pages+0x3db/0x720 lib/iov_iter.c:1646
dio_refill_pages fs/direct-io.c:173 [inline]
dio_get_page fs/direct-io.c:214 [inline]
do_direct_IO fs/direct-io.c:916 [inline]
__blockdev_direct_IO+0x150a/0x49b0 fs/direct-io.c:1249
blockdev_direct_IO include/linux/fs.h:3182 [inline]
exfat_direct_IO+0x1b4/0x3d0 fs/exfat/inode.c:526
generic_file_read_iter+0x231/0x430 mm/filemap.c:2783
aio_read+0x364/0x500 fs/aio.c:1611
io_submit_one+0x884/0x18b0 fs/aio.c:2061
__do_sys_io_submit fs/aio.c:2120 [inline]
__se_sys_io_submit+0x179/0x2f0 fs/aio.c:2090
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
&mm->mmap_lock --> sb_pagefaults#3 --> &sb->s_type->i_mutex_key#29

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sb->s_type->i_mutex_key#29);
lock(sb_pagefaults#3);
lock(&sb->s_type->i_mutex_key#29);
rlock(&mm->mmap_lock);

*** DEADLOCK ***

1 lock held by syz-executor.2/9254:
#0: ffff88806a3c3d80 (&sb->s_type->i_mutex_key#29){++++}-{3:3}, at: inode_lock include/linux/fs.h:791 [inline]
#0: ffff88806a3c3d80 (&sb->s_type->i_mutex_key#29){++++}-{3:3}, at: __blockdev_direct_IO+0x346/0x49b0 fs/direct-io.c:1146

stack backtrace:
CPU: 0 PID: 9254 Comm: syz-executor.2 Not tainted 6.9.0-rc4-next-20240416-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
gup_fast_fallback+0x24c/0x2b40 mm/gup.c:3442
pin_user_pages_fast+0xcc/0x160 mm/gup.c:3566
iov_iter_extract_user_pages lib/iov_iter.c:1583 [inline]
iov_iter_extract_pages+0x3db/0x720 lib/iov_iter.c:1646
dio_refill_pages fs/direct-io.c:173 [inline]
dio_get_page fs/direct-io.c:214 [inline]
do_direct_IO fs/direct-io.c:916 [inline]
__blockdev_direct_IO+0x150a/0x49b0 fs/direct-io.c:1249
blockdev_direct_IO include/linux/fs.h:3182 [inline]
exfat_direct_IO+0x1b4/0x3d0 fs/exfat/inode.c:526
generic_file_read_iter+0x231/0x430 mm/filemap.c:2783
aio_read+0x364/0x500 fs/aio.c:1611
io_submit_one+0x884/0x18b0 fs/aio.c:2061
__do_sys_io_submit fs/aio.c:2120 [inline]
__se_sys_io_submit+0x179/0x2f0 fs/aio.c:2090
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f397947dea9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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:00007f397a1670c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1
RAX: ffffffffffffffda RBX: 00007f39795abf80 RCX: 00007f397947dea9
RDX: 0000000020000540 RSI: 0000000000003f0a RDI: 00007f397a13d000
RBP: 00007f39794ca4a4 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f39795abf80 R15: 00007ffd43409678
</TASK>


---
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