[syzbot] [exfat?] possible deadlock in exfat_page_mkwrite

From: syzbot
Date: Tue Apr 16 2024 - 09:14:41 EST

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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=15817767180000
kernel config: https://syzkaller.appspot.com/x/.config?x=c247afaa437e6409
dashboard link: https://syzkaller.appspot.com/bug?extid=d88216a7af9446d57d59
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+d88216a7af9446d57d59@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.9.0-rc4-next-20240416-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/17125 is trying to acquire lock:
ffff88805e616b38 (&sb->s_type->i_mutex_key#24){++++}-{3:3}, at: inode_lock include/linux/fs.h:791 [inline]
ffff88805e616b38 (&sb->s_type->i_mutex_key#24){++++}-{3:3}, at: exfat_page_mkwrite+0x43a/0xea0 fs/exfat/file.c:629

but task is already holding lock:
ffff88802dc76518 (sb_pagefaults#4){.+.+}-{0:0}, at: do_page_mkwrite+0x19b/0x480 mm/memory.c:3097

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (sb_pagefaults#4){.+.+}-{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
__put_user_4+0x11/0x20 arch/x86/lib/putuser.S:86
__sys_socketpair+0x186/0x720 net/socket.c:1756
__do_sys_socketpair net/socket.c:1822 [inline]
__se_sys_socketpair net/socket.c:1819 [inline]
__x64_sys_socketpair+0x9b/0xb0 net/socket.c:1819
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

-> #1 (&mm->mmap_lock){++++}-{3:3}:
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
new_sync_read fs/read_write.c:395 [inline]
vfs_read+0x9c4/0xbd0 fs/read_write.c:476
ksys_read+0x1a0/0x2c0 fs/read_write.c:619
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

-> #0 (&sb->s_type->i_mutex_key#24){++++}-{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
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

other info that might help us debug this:

Chain exists of:
&sb->s_type->i_mutex_key#24 --> &mm->mmap_lock --> sb_pagefaults#4

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
rlock(sb_pagefaults#4);
lock(&mm->mmap_lock);
lock(sb_pagefaults#4);
lock(&sb->s_type->i_mutex_key#24);

*** DEADLOCK ***

2 locks held by syz-executor.0/17125:
#0: ffff88804e4ce098 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:163 [inline]
#0: ffff88804e4ce098 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5692 [inline]
#0: ffff88804e4ce098 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x32/0x2f0 mm/memory.c:5752
#1: ffff88802dc76518 (sb_pagefaults#4){.+.+}-{0:0}, at: do_page_mkwrite+0x19b/0x480 mm/memory.c:3097

stack backtrace:
CPU: 1 PID: 17125 Comm: syz-executor.0 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
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
RIP: 0033:0x7f59f325f107
Code: 7e 6f 44 16 e0 48 29 fe 48 83 e1 e0 48 01 ce 0f 1f 40 00 c5 fe 6f 4e 60 c5 fe 6f 56 40 c5 fe 6f 5e 20 c5 fe 6f 26 48 83 c6 80 <c5> fd 7f 49 60 c5 fd 7f 51 40 c5 fd 7f 59 20 c5 fd 7f 21 48 83 c1
RSP: 002b:00007ffd52a03428 EFLAGS: 00010203
RAX: 00000000200027c0 RBX: 0000000000000004 RCX: 0000000020003c20
RDX: 0000000000001500 RSI: 00007f59f2e02adf RDI: 00000000200027c0
RBP: 00007f59f33ac050 R08: 0000000000000000 R09: 0000000000000054
R10: 0000000000000000 R11: 0000000000000001 R12: 00007ffd52a035e0
R13: 0000000000000001 R14: ffffffffffffffff R15: 00007f59f3234cb0
</TASK>

---
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Next message: syzbot: "[syzbot] [btrfs?] KMSAN: kernel-infoleak in btrfs_ioctl_logical_to_ino (2)"
Previous message: Yunsheng Lin: "Re: [PATCH net-next v2 13/15] net: replace page_frag with page_frag_cache"
Next in thread: Dave Chinner: "Re: [syzbot] [exfat?] possible deadlock in exfat_page_mkwrite"
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