possible deadlock in get_user_pages_unlocked (2)

Status: closed as invalid on 2019/06/23 22:16
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+e1374b2ec8f6a25ab2e5@syzkaller.appspotmail.com
First crash: 2636d, last: 2632d
Cause bisection: introduced by (bisect log) :
commit 69d61f577d147b396be0991b2ac6f65057f7d445
Author: Mimi Zohar <zohar@linux.ibm.com>
Date: Wed Apr 3 21:47:46 2019 +0000

  ima: verify mprotect change is consistent with mmap policy

Crash: possible deadlock in get_user_pages_unlocked (log)
Repro: C syz .config
  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
possible deadlock in get_user_pages_unlocked (2) 1 (4) 2019/06/10 19:06
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in get_user_pages_unlocked mm 4 syz, C 5 3097d 3120d 4/29 fixed on 2018/03/23 18:14

Sample crash report:
IPVS: ftp: loaded support on port[0] = 21
======================================================
WARNING: possible circular locking dependency detected
5.2.0-rc3-next-20190604 #8 Not tainted
------------------------------------------------------
syz-executor842/8767 is trying to acquire lock:
00000000badb3a6d (&mm->mmap_sem#2){++++}, at: get_user_pages_unlocked+0xfc/0x4a0 mm/gup.c:1174

but task is already holding lock:
0000000052562d44 (&sb->s_type->i_mutex_key#10){+.+.}, at: inode_trylock include/linux/fs.h:798 [inline]
0000000052562d44 (&sb->s_type->i_mutex_key#10){+.+.}, at: ext4_file_write_iter+0x246/0x1070 fs/ext4/file.c:232

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sb->s_type->i_mutex_key#10){+.+.}:
       down_write+0x38/0xa0 kernel/locking/rwsem.c:66
       inode_lock include/linux/fs.h:778 [inline]
       process_measurement+0x15ae/0x15e0 security/integrity/ima/ima_main.c:228
       ima_file_mmap+0x11a/0x130 security/integrity/ima/ima_main.c:370
       security_file_mprotect+0xd5/0x100 security/security.c:1426
       do_mprotect_pkey+0x537/0xa30 mm/mprotect.c:550
       __do_sys_mprotect mm/mprotect.c:582 [inline]
       __se_sys_mprotect mm/mprotect.c:579 [inline]
       __x64_sys_mprotect+0x78/0xb0 mm/mprotect.c:579
       do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 (&mm->mmap_sem#2){++++}:
       lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4300
       down_read+0x3f/0x1e0 kernel/locking/rwsem.c:24
       get_user_pages_unlocked+0xfc/0x4a0 mm/gup.c:1174
       __gup_longterm_unlocked mm/gup.c:2193 [inline]
       get_user_pages_fast+0x43f/0x530 mm/gup.c:2245
       iov_iter_get_pages+0x2c2/0xf80 lib/iov_iter.c:1287
       dio_refill_pages fs/direct-io.c:171 [inline]
       dio_get_page fs/direct-io.c:215 [inline]
       do_direct_IO fs/direct-io.c:983 [inline]
       do_blockdev_direct_IO+0x3f7b/0x8e00 fs/direct-io.c:1336
       __blockdev_direct_IO+0xa1/0xca fs/direct-io.c:1422
       ext4_direct_IO_write fs/ext4/inode.c:3782 [inline]
       ext4_direct_IO+0xaa7/0x1bb0 fs/ext4/inode.c:3909
       generic_file_direct_write+0x20a/0x4a0 mm/filemap.c:3110
       __generic_file_write_iter+0x2ee/0x630 mm/filemap.c:3293
       ext4_file_write_iter+0x332/0x1070 fs/ext4/file.c:266
       call_write_iter include/linux/fs.h:1870 [inline]
       new_sync_write+0x4d3/0x770 fs/read_write.c:483
       __vfs_write+0xe1/0x110 fs/read_write.c:496
       vfs_write+0x268/0x5d0 fs/read_write.c:558
       ksys_write+0x14f/0x290 fs/read_write.c:611
       __do_sys_write fs/read_write.c:623 [inline]
       __se_sys_write fs/read_write.c:620 [inline]
       __x64_sys_write+0x73/0xb0 fs/read_write.c:620
       do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#10);
                               lock(&mm->mmap_sem#2);
                               lock(&sb->s_type->i_mutex_key#10);
  lock(&mm->mmap_sem#2);

 *** DEADLOCK ***

2 locks held by syz-executor842/8767:
 #0: 0000000065e8e19a (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2836 [inline]
 #0: 0000000065e8e19a (sb_writers#3){.+.+}, at: vfs_write+0x485/0x5d0 fs/read_write.c:557
 #1: 0000000052562d44 (&sb->s_type->i_mutex_key#10){+.+.}, at: inode_trylock include/linux/fs.h:798 [inline]
 #1: 0000000052562d44 (&sb->s_type->i_mutex_key#10){+.+.}, at: ext4_file_write_iter+0x246/0x1070 fs/ext4/file.c:232

stack backtrace:
CPU: 0 PID: 8767 Comm: syz-executor842 Not tainted 5.2.0-rc3-next-20190604 #8
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 print_circular_bug.cold+0x1cc/0x28f kernel/locking/lockdep.c:1566
 check_prev_add kernel/locking/lockdep.c:2311 [inline]
 check_prevs_add kernel/locking/lockdep.c:2419 [inline]
 validate_chain kernel/locking/lockdep.c:2801 [inline]
 __lock_acquire+0x3755/0x5490 kernel/locking/lockdep.c:3790
 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4300
 down_read+0x3f/0x1e0 kernel/locking/rwsem.c:24
 get_user_pages_unlocked+0xfc/0x4a0 mm/gup.c:1174
 __gup_longterm_unlocked mm/gup.c:2193 [inline]
 get_user_pages_fast+0x43f/0x530 mm/gup.c:2245
 iov_iter_get_pages+0x2c2/0xf80 lib/iov_iter.c:1287
 dio_refill_pages fs/direct-io.c:171 [inline]
 dio_get_page fs/direct-io.c:215 [inline]
 do_direct_IO fs/direct-io.c:983 [inline]
 do_blockdev_direct_IO+0x3f7b/0x8e00 fs/direct-io.c:1336
 ? 0xffffffff81000000
 __blockdev_direct_IO+0xa1/0xca fs/direct-io.c:1422
 ext4_direct_IO_write fs/ext4/inode.c:3782 [inline]
 ext4_direct_IO+0xaa7/0x1bb0 fs/ext4/inode.c:3909
 generic_file_direct_write+0x20a/0x4a0 mm/filemap.c:3110
 __generic_file_write_iter+0x2ee/0x630 mm/filemap.c:3293
 ext4_file_write_iter+0x332/0x1070 fs/ext4/file.c:266
 call_write_iter include/linux/fs.h:1870 [inline]
 new_sync_write+0x4d3/0x770 fs/read_write.c:483
 __vfs_write+0xe1/0x110 fs/read_write.c:496
 vfs_write+0x268/0x5d0 fs/read_write.c:558
 ksys_write+0x14f/0x290 fs/read_write.c:611
 __do_sys_write fs/read_write.c:623 [inline]
 __se_sys_write fs/read_write.c:620 [inline]
 __x64_sys_write+0x73/0xb0 fs/read_write.c:620
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x440a49
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 0f 83 bb 10 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc18e28968 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000004a22e0 RCX: 0000000000440a49
RDX: 0000000020000012 RSI: 0000000020000000 RDI: 0000000000000005
RBP: 00000000004a2370 R08: 0000000000000012 R09: 0000000000000100
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401f90
R13: 0000000000402020 R14: 0000000000000000 R15: 0000000000000000

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2019/06/04 21:18 linux-next 56b697c6c13b e41a20c5 .config console log report syz C ci-upstream-linux-next-kasan-gce-root
2019/06/04 19:06 linux-next 56b697c6c13b e41a20c5 .config console log report ci-upstream-linux-next-kasan-gce-root
2019/06/04 19:03 linux-next 56b697c6c13b e41a20c5 .config console log report ci-upstream-linux-next-kasan-gce-root
2019/06/01 02:17 linux-next 3c09c1950c84 53c81ea5 .config console log report ci-upstream-linux-next-kasan-gce-root
* Struck through repros no longer work on HEAD.