linux-kernel - Re: possible deadlock in process

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Date:   Thu, 11 Jul 2019 14:25:33 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     syzbot <syzbot+5ab61747675a87ea359d@...kaller.appspotmail.com>,
        dmitry.kasatkin@...il.com, jmorris@...ei.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, serge@...lyn.com,
        syzkaller-bugs@...glegroups.com, zohar@...ux.vnet.ibm.com
Subject: Re: possible deadlock in process_measurement

Hi Eric,

On Mon, 2019-06-03 at 09:35 -0700, syzbot wrote:
> syzbot has found a reproducer for the following crash on:
> 
> HEAD commit:    3c09c195 Add linux-next specific files for 20190531
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10f61a0ea00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6cfb24468280cd5c
> dashboard link: https://syzkaller.appspot.com/bug?extid=5ab61747675a87ea359d
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=177c3d16a00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14ec01baa00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+5ab61747675a87ea359d@...kaller.appspotmail.com
> 
> get_swap_device: Bad swap file entry 6000000000000001
> get_swap_device: Bad swap file entry 6400000000000001
> get_swap_device: Bad swap file entry 6800000000000001
> get_swap_device: Bad swap file entry 6c00000000000001
> get_swap_device: Bad swap file entry 7000000000000001
> get_swap_device: Bad swap file entry 7400000000000001
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.2.0-rc2-next-20190531 #4 Not tainted
> ------------------------------------------------------
> syz-executor395/17373 is trying to acquire lock:
> 000000003d1a4a53 (&sb->s_type->i_mutex_key#10){+.+.}, at: inode_lock  
> include/linux/fs.h:778 [inline]
> 000000003d1a4a53 (&sb->s_type->i_mutex_key#10){+.+.}, at:  
> process_measurement+0x15ae/0x15e0 security/integrity/ima/ima_main.c:228
> 
> but task is already holding lock:
> 00000000e0714fc5 (&mm->mmap_sem#2){++++}, at: do_mprotect_pkey+0x1f6/0xa30  
> mm/mprotect.c:485
> 
> which lock already depends on the new lock.

More information is needed here.  Missing is the IMA policy.  In
particular whether the IMA policy has "permit_directio" enabled?  Is
it enabled for all files or particular ones.  If I'm reading the log
properly, it looks like the IMA mmap policy rule does not exclude the
pemitted_directio files.

Do you have any suggestions on how to resolve this?

Mimi

> 
> 
> the existing dependency chain (in reverse order) is:
> 
> -> #1 (&mm->mmap_sem#2){++++}:
>         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
> 
> -> #0 (&sb->s_type->i_mutex_key#10){+.+.}:
>         lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4300
>         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:1430
>         do_mprotect_pkey+0x537/0xa30 mm/mprotect.c:550
>         __do_sys_pkey_mprotect mm/mprotect.c:590 [inline]
>         __se_sys_pkey_mprotect mm/mprotect.c:587 [inline]
>         __x64_sys_pkey_mprotect+0x97/0xf0 mm/mprotect.c:587
>         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(&mm->mmap_sem#2);
>                                 lock(&sb->s_type->i_mutex_key#10);
>                                 lock(&mm->mmap_sem#2);
>    lock(&sb->s_type->i_mutex_key#10);
> 
>   *** DEADLOCK ***
> 
> 1 lock held by syz-executor395/17373:
>   #0: 00000000e0714fc5 (&mm->mmap_sem#2){++++}, at:  
> do_mprotect_pkey+0x1f6/0xa30 mm/mprotect.c:485
> 
> stack backtrace:
> CPU: 1 PID: 17373 Comm: syz-executor395 Not tainted 5.2.0-rc2-next-20190531  
> #4
> 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_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:1430
>   do_mprotect_pkey+0x537/0xa30 mm/mprotect.c:550
>   __do_sys_pkey_mprotect mm/mprotect.c:590 [inline]
>   __se_sys_pkey_mprotect mm/mprotect.c:587 [inline]
>   __x64_sys_pkey_mprotect+0x97/0xf0 mm/mprotect.c:587
>   do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x440279
> 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 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffeec2f48d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000149
> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440279
> RDX: 000000000000000
>