Re: possible deadlock in get_user_pages_unlocked (2)

From: syzbot
Date: Tue Jun 04 2019 - 17:23:04 EST

Next message: sean.wang: "[PATCH net v1] net: ethernet: mediatek: Fixed several errors caused by undefined symbols"
Previous message: Paul E. McKenney: "Re: rcu_read_lock lost its compiler barrier"
In reply to: syzbot: "possible deadlock in get_user_pages_unlocked (2)"
Next in thread: syzbot: "Re: possible deadlock in get_user_pages_unlocked (2)"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

syzbot has found a reproducer for the following crash on:

HEAD commit: 56b697c6 Add linux-next specific files for 20190604
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13241716a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=4248d6bc70076f7d
dashboard link: https://syzkaller.appspot.com/bug?extid=e1374b2ec8f6a25ab2e5
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=165757eea00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10dd3e86a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e1374b2ec8f6a25ab2e5@xxxxxxxxxxxxxxxxxxxxxxxxx

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

Next message: sean.wang: "[PATCH net v1] net: ethernet: mediatek: Fixed several errors caused by undefined symbols"
Previous message: Paul E. McKenney: "Re: rcu_read_lock lost its compiler barrier"
In reply to: syzbot: "possible deadlock in get_user_pages_unlocked (2)"
Next in thread: syzbot: "Re: possible deadlock in get_user_pages_unlocked (2)"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]