[syzbot] WARNING in anon_vma_name

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f8f60f322f06 Add linux-next specific files for 20221111
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=12f0f3fe880000
kernel config: https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
dashboard link: https://syzkaller.appspot.com/bug?extid=62ed954113bf02c79f74
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=171f6c49880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16fdfd99880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6008df424195/disk-f8f60f32.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/394340525f66/vmlinux-f8f60f32.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b13604a3343a/bzImage-f8f60f32.xz

The issue was bisected to:

commit 2220e3a8953e86b87adfc753fc57c2a5e0b0a032
Author: Pasha Tatashin <pasha.t...@soleen.com>
Date: Mon Nov 7 18:47:15 2022 +0000

mm: anonymous shared memory naming

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16d32f66880000
final oops: https://syzkaller.appspot.com/x/report.txt?x=15d32f66880000
console output: https://syzkaller.appspot.com/x/log.txt?x=11d32f66880000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+62ed95...@syzkaller.appspotmail.com
Fixes: 2220e3a8953e ("mm: anonymous shared memory naming")

------------[ cut here ]------------
WARNING: CPU: 0 PID: 5239 at include/linux/mmap_lock.h:155 mmap_assert_locked include/linux/mmap_lock.h:155 [inline]
WARNING: CPU: 0 PID: 5239 at include/linux/mmap_lock.h:155 anon_vma_name+0x11c/0x170 mm/madvise.c:97
Modules linked in:
CPU: 1 PID: 5239 Comm: syz-executor276 Not tainted 6.1.0-rc4-next-20221111-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022
RIP: 0010:mmap_assert_locked include/linux/mmap_lock.h:155 [inline]
RIP: 0010:anon_vma_name+0x11c/0x170 mm/madvise.c:97
Code: 8d bd 58 01 00 00 be ff ff ff ff e8 1e fc e0 07 31 ff 41 89 c4 89 c6 e8 c2 27 bc ff 45 85 e4 0f 85 5c ff ff ff e8 e4 2a bc ff <0f> 0b e9 50 ff ff ff e8 d8 2a bc ff 48 89 ef e8 00 e7 f2 ff 0f 0b
RSP: 0018:ffffc90003c7f810 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffffffff8b9ae000 RCX: 0000000000000000
RDX: ffff88801d5fba80 RSI: ffffffff81c0a28c RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffffffff8b9ae008 R14: ffffffff8b9ae010 R15: 0000000000000000
FS: 0000555556387300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000061ba0c CR3: 000000007d6c4000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
show_map_vma+0x22d/0x620 fs/proc/task_mmu.c:297
show_smap+0xe4/0x490 fs/proc/task_mmu.c:866
traverse.part.0+0xcf/0x5f0 fs/seq_file.c:111
traverse fs/seq_file.c:101 [inline]
seq_read_iter+0x90f/0x1280 fs/seq_file.c:195
seq_read+0x16d/0x210 fs/seq_file.c:162
do_loop_readv_writev fs/read_write.c:756 [inline]
do_loop_readv_writev fs/read_write.c:743 [inline]
do_iter_read+0x4f8/0x750 fs/read_write.c:798
vfs_readv+0xe5/0x150 fs/read_write.c:916
do_preadv fs/read_write.c:1008 [inline]
__do_sys_preadv fs/read_write.c:1058 [inline]
__se_sys_preadv fs/read_write.c:1053 [inline]
__x64_sys_preadv+0x22b/0x310 fs/read_write.c:1053
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f545e62b239
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffed9c02fe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f545e62b239
RDX: 0000000000000001 RSI: 00000000200006c0 RDI: 0000000000000003
RBP: 00007ffed9c02ff0 R08: 0000000000000000 R09: 65732f636f72702f
R10: 00000000fffffffe R11: 0000000000000246 R12: 00007f545e5ef120
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Hillf Danton]

On 13 Nov 2022 22:28:39 -0800

> syzbot found the following issue on:
>
> HEAD commit: f8f60f322f06 Add linux-next specific files for 20221111
> git tree: linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=12f0f3fe880000
> kernel config: https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
> dashboard link: https://syzkaller.appspot.com/bug?extid=62ed954113bf02c79f74
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=171f6c49880000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16fdfd99880000

Take mmap_lock for read for getting anon_vma_name in a bid to quiesce the warning.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git f8f60f322f06

--- x/fs/proc/task_mmu.c
+++ t/fs/proc/task_mmu.c
@@ -277,7 +277,7 @@ show_map_vma(struct seq_file *m, struct
struct mm_struct *mm = vma->vm_mm;
struct file *file = vma->vm_file;
vm_flags_t flags = vma->vm_flags;
- struct anon_vma_name *anon_name;
+ struct anon_vma_name *anon_name = NULL;
unsigned long ino = 0;
unsigned long long pgoff = 0;
unsigned long start, end;
@@ -294,7 +294,13 @@ show_map_vma(struct seq_file *m, struct
start = vma->vm_start;
end = vma->vm_end;
show_vma_header_prefix(m, start, end, flags, pgoff, dev, ino);
- anon_name = anon_vma_name(vma);
+ if (mm) {
+ if (mmap_read_lock_killable(mm))
+ goto done;
+ anon_name = anon_vma_name(vma);
+ anon_vma_name_get(anon_name);
+ mmap_read_unlock(mm);
+ }

/*
* Print the dentry name for named mappings, and a
@@ -349,6 +355,7 @@ done:
seq_puts(m, name);
}
seq_putc(m, '\n');
+ anon_vma_name_put(anon_name);
}

static int show_map(struct seq_file *m, void *v)
--

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
possible deadlock in show_map_vma

============================================
WARNING: possible recursive locking detected
6.1.0-rc4-next-20221111-syzkaller-dirty #0 Not tainted
--------------------------------------------
syz-executor.0/5772 is trying to acquire lock:
ffff88807dd89b98 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock_killable include/linux/mmap_lock.h:126 [inline]
ffff88807dd89b98 (&mm->mmap_lock){++++}-{3:3}, at: show_map_vma+0x1dd/0x8a0 fs/proc/task_mmu.c:298

but task is already holding lock:
ffff88807dd89b98 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock_killable include/linux/mmap_lock.h:126 [inline]
ffff88807dd89b98 (&mm->mmap_lock){++++}-{3:3}, at: m_start+0x1d6/0x670 fs/proc/task_mmu.c:162

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(&mm->mmap_lock);
lock(&mm->mmap_lock);

*** DEADLOCK ***

May be due to missing lock nesting notation

2 locks held by syz-executor.0/5772:
#0: ffff88801d4c28b8 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xdf/0x1280 fs/seq_file.c:182
#1: ffff88807dd89b98 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock_killable include/linux/mmap_lock.h:126 [inline]
#1: ffff88807dd89b98 (&mm->mmap_lock){++++}-{3:3}, at: m_start+0x1d6/0x670 fs/proc/task_mmu.c:162

stack backtrace:
CPU: 1 PID: 5772 Comm: syz-executor.0 Not tainted 6.1.0-rc4-next-20221111-syzkaller-dirty #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022

Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_deadlock_bug kernel/locking/lockdep.c:2990 [inline]
check_deadlock kernel/locking/lockdep.c:3033 [inline]
validate_chain kernel/locking/lockdep.c:3818 [inline]
__lock_acquire.cold+0x116/0x3a7 kernel/locking/lockdep.c:5055
lock_acquire kernel/locking/lockdep.c:5668 [inline]
lock_acquire+0x1df/0x630 kernel/locking/lockdep.c:5633
down_read_killable+0x9b/0x490 kernel/locking/rwsem.c:1532
mmap_read_lock_killable include/linux/mmap_lock.h:126 [inline]
show_map_vma+0x1dd/0x8a0 fs/proc/task_mmu.c:298
show_smap+0xe4/0x490 fs/proc/task_mmu.c:873

traverse.part.0+0xcf/0x5f0 fs/seq_file.c:111
traverse fs/seq_file.c:101 [inline]
seq_read_iter+0x90f/0x1280 fs/seq_file.c:195
seq_read+0x16d/0x210 fs/seq_file.c:162
do_loop_readv_writev fs/read_write.c:756 [inline]
do_loop_readv_writev fs/read_write.c:743 [inline]
do_iter_read+0x4f8/0x750 fs/read_write.c:798
vfs_readv+0xe5/0x150 fs/read_write.c:916
do_preadv fs/read_write.c:1008 [inline]
__do_sys_preadv fs/read_write.c:1058 [inline]
__se_sys_preadv fs/read_write.c:1053 [inline]
__x64_sys_preadv+0x22b/0x310 fs/read_write.c:1053
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

RIP: 0033:0x7fdc27c8b639
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdc28980168 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00007fdc27dabf80 RCX: 00007fdc27c8b639

RDX: 0000000000000001 RSI: 00000000200006c0 RDI: 0000000000000003

RBP: 00007fdc27ce67e1 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000fffffffe R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc20c7d9af R14: 00007fdc28980300 R15: 0000000000022000
</TASK>


Tested on:

commit: f8f60f32 Add linux-next specific files for 20221111
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=13a0e2f1880000

kernel config: https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
dashboard link: https://syzkaller.appspot.com/bug?extid=62ed954113bf02c79f74
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=1069e0f1880000

[Hillf Danton]

On 13 Nov 2022 22:28:39 -0800

> syzbot found the following issue on:
>
> HEAD commit: f8f60f322f06 Add linux-next specific files for 20221111
> git tree: linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=12f0f3fe880000
> kernel config: https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
> dashboard link: https://syzkaller.appspot.com/bug?extid=62ed954113bf02c79f74
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=171f6c49880000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16fdfd99880000

In a bid to quiesce the warning, check mm to hold the right mmap_lock.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git f8f60f322f06

--- x/fs/proc/task_mmu.c
+++ t/fs/proc/task_mmu.c

@@ -274,6 +274,7 @@ static void show_vma_header_prefix(struc
static void
show_map_vma(struct seq_file *m, struct vm_area_struct *vma)
{
+ struct proc_maps_private *priv = m->private;

struct mm_struct *mm = vma->vm_mm;
struct file *file = vma->vm_file;
vm_flags_t flags = vma->vm_flags;

@@ -294,7 +295,11 @@ show_map_vma(struct seq_file *m, struct

start = vma->vm_start;
end = vma->vm_end;
show_vma_header_prefix(m, start, end, flags, pgoff, dev, ino);
- anon_name = anon_vma_name(vma);
+

+ if (mm == priv->mm)
+ anon_name = anon_vma_name(vma);
+ else
+ anon_name = NULL;

/*
* Print the dentry name for named mappings, and a

--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+62ed95...@syzkaller.appspotmail.com

Tested on:

commit: f8f60f32 Add linux-next specific files for 20221111
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git

console output: https://syzkaller.appspot.com/x/log.txt?x=175b0e35880000

kernel config: https://syzkaller.appspot.com/x/.config?x=85ba52c07cd97289
dashboard link: https://syzkaller.appspot.com/bug?extid=62ed954113bf02c79f74
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

patch: https://syzkaller.appspot.com/x/patch.diff?x=1751b9d1880000

Note: testing is done by a robot and is best-effort only.

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.