syzbot


possible deadlock in gup_fast_fallback

Status: upstream: reported on 2024/04/21 03:14
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+63ba90b81c16b86379bd@syzkaller.appspotmail.com
First crash: 31d, last: 31d
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [mm?] possible deadlock in gup_fast_fallback 0 (1) 2024/04/21 03:14

Sample crash report:
======================================================
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>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/04/17 03:03 linux-next 66e4190e92ce 18f6e127 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in gup_fast_fallback
2024/04/17 03:03 linux-next 66e4190e92ce 18f6e127 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in gup_fast_fallback
2024/04/17 03:03 linux-next 66e4190e92ce 18f6e127 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root possible deadlock in gup_fast_fallback
* Struck through repros no longer work on HEAD.