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Syzkaller reports the following problem:
BUG: sleeping function called from invalid context at kernel/printk/printk.c:2347
in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 1105, name: syz-executor423
3 locks held by syz-executor423/1105:
#0: ffff8881468b9098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x90 drivers/tty/tty_ldisc.c:266
#1: ffff8881468b9130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:952 [inline]
#1: ffff8881468b9130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:975 [inline]
#1: ffff8881468b9130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: file_tty_write.constprop.0+0x2a8/0x8e0 drivers/tty/tty_io.c:1118
#2: ffff88801b06c398 (&gsm->tx_lock){....}-{2:2}, at: gsmld_write+0x5e/0x150 drivers/tty/n_gsm.c:2717
irq event stamp: 3482
hardirqs last enabled at (3481): [<ffffffff81d13343>] __get_reqs_available+0x143/0x2f0 fs/aio.c:946
hardirqs last disabled at (3482): [<ffffffff87d39722>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]
hardirqs last disabled at (3482): [<ffffffff87d39722>] _raw_spin_lock_irqsave+0x52/0x60 kernel/locking/spinlock.c:159
softirqs last enabled at (3408): [<ffffffff87e01002>] asm_call_irq_on_stack+0x12/0x20
softirqs last disabled at (3401): [<ffffffff87e01002>] asm_call_irq_on_stack+0x12/0x20
Preemption disabled at:
[<0000000000000000>] 0x0
CPU: 2 PID: 1105 Comm: syz-executor423 Not tainted 5.10.137-syzkaller #0
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x107/0x167 lib/dump_stack.c:118
___might_sleep.cold+0x1e8/0x22e kernel/sched/core.c:7304
console_lock+0x19/0x80 kernel/printk/printk.c:2347
do_con_write+0x113/0x1de0 drivers/tty/vt/vt.c:2909
con_write+0x22/0xc0 drivers/tty/vt/vt.c:3296
gsmld_write+0xd0/0x150 drivers/tty/n_gsm.c:2720
do_tty_write drivers/tty/tty_io.c:1028 [inline]
file_tty_write.constprop.0+0x502/0x8e0 drivers/tty/tty_io.c:1118
call_write_iter include/linux/fs.h:1903 [inline]
aio_write+0x355/0x7b0 fs/aio.c:1580
__io_submit_one fs/aio.c:1952 [inline]
io_submit_one+0xf45/0x1a90 fs/aio.c:1999
__do_sys_io_submit fs/aio.c:2058 [inline]
__se_sys_io_submit fs/aio.c:2028 [inline]
__x64_sys_io_submit+0x18c/0x2f0 fs/aio.c:2028
do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xc6
The problem happens in the following control flow:
gsmld_write(...)
spin_lock_irqsave(&gsm->tx_lock, flags) // taken a spinlock on TX data
con_write(...)
do_con_write(...)
console_lock()
might_sleep() // -> bug
As far as console_lock() might sleep it should not be called with
spinlock held.
The patch replaces tx_lock spinlock with mutex in order to avoid the
problem.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Fixes: 32dd59f969 ("tty: n_gsm: fix race condition in gsmld_write()")
Cc: stable <stable@kernel.org>
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Link: https://lore.kernel.org/r/20220829131640.69254-3-pchelkin@ispras.ru
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
902e02ea93