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Date: Tue, 16 Apr 2024 06:14:20 -0700
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Subject: [syzbot] [exfat?] possible deadlock in exfat_page_mkwrite
From: syzbot <syzbot+d88216a7af9446d57d59@syzkaller.appspotmail.com>
To: linkinjeon@kernel.org, linux-fsdevel@vger.kernel.org, 
	linux-kernel@vger.kernel.org, sj1557.seo@samsung.com, 
	syzkaller-bugs@googlegroups.com
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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@syzkaller.appspotmail.com

======================================================
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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