[syzbot] INFO: trying to register non-static key in gsmld_write

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ca688bff68bc Add linux-next specific files for 20220808
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1339918e080000
kernel config: https://syzkaller.appspot.com/x/.config?x=4c20e006003cdecb
dashboard link: https://syzkaller.appspot.com/bug?extid=cf155def4e717db68a12
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cf155d...@syzkaller.appspotmail.com

INFO: trying to register non-static key.
The code is fine but needs lockdep annotation, or maybe
you didn't initialize this object before use?
turning off the locking correctness validator.
CPU: 0 PID: 3731 Comm: syz-executor.0 Not tainted 5.19.0-next-20220808-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
assign_lock_key kernel/locking/lockdep.c:979 [inline]
register_lock_class+0xf1b/0x1120 kernel/locking/lockdep.c:1292
__lock_acquire+0x109/0x56d0 kernel/locking/lockdep.c:4932
lock_acquire kernel/locking/lockdep.c:5666 [inline]
lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162
gsmld_write+0x5e/0x140 drivers/tty/n_gsm.c:3023
do_tty_write drivers/tty/tty_io.c:1024 [inline]
file_tty_write.constprop.0+0x499/0x8f0 drivers/tty/tty_io.c:1095
call_write_iter include/linux/fs.h:2192 [inline]
do_iter_readv_writev+0x20b/0x3b0 fs/read_write.c:729
do_iter_write+0x182/0x700 fs/read_write.c:855
vfs_writev+0x1aa/0x630 fs/read_write.c:928
do_writev+0x133/0x2f0 fs/read_write.c:971
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: 0033:0x7fd570e89279
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:00007fd572050168 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007fd570f9bf80 RCX: 00007fd570e89279
RDX: 0000000000000001 RSI: 0000000020000480 RDI: 0000000000000003
RBP: 00007fd570ee3189 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc4cf5714f R14: 00007fd572050300 R15: 0000000000022000
</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:
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: ca688bff68bc Add linux-next specific files for 20220808
git tree: linux-next

console+strace: https://syzkaller.appspot.com/x/log.txt?x=16c4c201080000

kernel config: https://syzkaller.appspot.com/x/.config?x=4c20e006003cdecb
dashboard link: https://syzkaller.appspot.com/bug?extid=cf155def4e717db68a12
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=151f2b46080000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=143a3171080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cf155d...@syzkaller.appspotmail.com

INFO: trying to register non-static key.
The code is fine but needs lockdep annotation, or maybe
you didn't initialize this object before use?
turning off the locking correctness validator.

CPU: 0 PID: 3608 Comm: syz-executor156 Not tainted 5.19.0-next-20220808-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
assign_lock_key kernel/locking/lockdep.c:979 [inline]
register_lock_class+0xf1b/0x1120 kernel/locking/lockdep.c:1292
__lock_acquire+0x109/0x56d0 kernel/locking/lockdep.c:4932
lock_acquire kernel/locking/lockdep.c:5666 [inline]
lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162
gsmld_write+0x5e/0x140 drivers/tty/n_gsm.c:3023
do_tty_write drivers/tty/tty_io.c:1024 [inline]
file_tty_write.constprop.0+0x499/0x8f0 drivers/tty/tty_io.c:1095
call_write_iter include/linux/fs.h:2192 [inline]

new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x9e9/0xdd0 fs/read_write.c:578
ksys_write+0x127/0x250 fs/read_write.c:631

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: 0033:0x7f80104e30c9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 81 14 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8010474268 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f801056b4d0 RCX: 00007f80104e30c9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f8010539010 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f8010474280
R13: 6d74702f7665642f R14: 00007f801047427c R15: 00007f801056b4d8
</TASK>

[Jiri Slaby]

Cc Daniel

--
js
suse labs

[Hillf Danton]

On Mon, 08 Aug 2022 06:21:24 -0700

>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: ca688bff68bc Add linux-next specific files for 20220808
> git tree: linux-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=16c4c201080000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4c20e006003cdecb
> dashboard link: https://syzkaller.appspot.com/bug?extid=cf155def4e717db68a12
> 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=151f2b46080000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=143a3171080000

See if gsm is active in the write path.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git ca688bff68bc

--- a/drivers/tty/n_gsm.c
+++ n/drivers/tty/n_gsm.c
@@ -3016,7 +3016,7 @@ static ssize_t gsmld_write(struct tty_st
int space;
int ret;

- if (!gsm)
+ if (!gsm || gsm->dead || !gsm->receive)
return -ENODEV;

ret = -ENOBUFS;
--

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+cf155d...@syzkaller.appspotmail.com

Tested on:

commit: ca688bff Add linux-next specific files for 20220808
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=10fd0705080000

kernel config: https://syzkaller.appspot.com/x/.config?x=4c20e006003cdecb
dashboard link: https://syzkaller.appspot.com/bug?extid=cf155def4e717db68a12
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=168d3fe1080000

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

[Tetsuo Handa]

syzbot is reporting use of uninitialized spinlock at gsmld_write() [1], for
commit 32dd59f96924f45e ("tty: n_gsm: fix race condition in gsmld_write()")
allows accessing gsm->tx_lock before gsm_activate_mux() initializes it.

Since object initialization should be done right after allocation in order
to avoid accessing uninitialized memory, move initialization of
timer/work/waitqueue/spinlock from gsmld_open()/gsm_activate_mux() to
gsm_alloc_mux().

Link: https://syzkaller.appspot.com/bug?extid=cf155def4e717db68a12 [1]
Reported-by: syzbot <syzbot+cf155d...@syzkaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin...@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+cf155d...@syzkaller.appspotmail.com>
Fixes: 32dd59f96924f45e ("tty: n_gsm: fix race condition in gsmld_write()")
---
drivers/tty/n_gsm.c | 17 ++++++-----------
1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index caa5c14ed57f..70cd90474679 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2501,13 +2501,6 @@ static int gsm_activate_mux(struct gsm_mux *gsm)
if (dlci == NULL)
return -ENOMEM;

- timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
- timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
- INIT_WORK(&gsm->tx_work, gsmld_write_task);
- init_waitqueue_head(&gsm->event);
- spin_lock_init(&gsm->control_lock);
- spin_lock_init(&gsm->tx_lock);
-
if (gsm->encoding == 0)
gsm->receive = gsm0_receive;
else
@@ -2612,6 +2605,12 @@ static struct gsm_mux *gsm_alloc_mux(void)
kref_init(&gsm->ref);
INIT_LIST_HEAD(&gsm->tx_ctrl_list);
INIT_LIST_HEAD(&gsm->tx_data_list);
+ timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
+ timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
+ INIT_WORK(&gsm->tx_work, gsmld_write_task);
+ init_waitqueue_head(&gsm->event);
+ spin_lock_init(&gsm->control_lock);
+ spin_lock_init(&gsm->tx_lock);

gsm->t1 = T1;
gsm->t2 = T2;
@@ -2946,10 +2945,6 @@ static int gsmld_open(struct tty_struct *tty)

gsmld_attach_gsm(tty, gsm);

- timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
- timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
- INIT_WORK(&gsm->tx_work, gsmld_write_task);
-
return 0;
}

--
2.34.1

[Jiri Slaby]

On 27. 08. 22, 15:47, Tetsuo Handa wrote:
> syzbot is reporting use of uninitialized spinlock at gsmld_write() [1], for
> commit 32dd59f96924f45e ("tty: n_gsm: fix race condition in gsmld_write()")
> allows accessing gsm->tx_lock before gsm_activate_mux() initializes it.
>
> Since object initialization should be done right after allocation in order
> to avoid accessing uninitialized memory, move initialization of
> timer/work/waitqueue/spinlock from gsmld_open()/gsm_activate_mux() to
> gsm_alloc_mux().

LGTM, I wonder why this was not like this forever.

Acked-by: Jiri Slaby <jiri...@kernel.org>

js
suse labs