From: Fedor Pchelkin pchelkin@ispras.ru
commit 902e02ea9385373ce4b142576eef41c642703955 upstream.
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: 32dd59f ("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 --- drivers/tty/n_gsm.c | 39 ++++++++++++++++++--------------------- 1 file changed, 18 insertions(+), 21 deletions(-)
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index c2212f52a603..c91a3004931f 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -235,7 +235,7 @@ struct gsm_mux { int old_c_iflag; /* termios c_iflag value before attach */ bool constipated; /* Asked by remote to shut up */
- spinlock_t tx_lock; + struct mutex tx_mutex; unsigned int tx_bytes; /* TX data outstanding */ #define TX_THRESH_HI 8192 #define TX_THRESH_LO 2048 @@ -820,15 +820,14 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg) * * Add data to the transmit queue and try and get stuff moving * out of the mux tty if not already doing so. Take the - * the gsm tx lock and dlci lock. + * the gsm tx mutex and dlci lock. */
static void gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg) { - unsigned long flags; - spin_lock_irqsave(&dlci->gsm->tx_lock, flags); + mutex_lock(&dlci->gsm->tx_mutex); __gsm_data_queue(dlci, msg); - spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags); + mutex_unlock(&dlci->gsm->tx_mutex); }
/** @@ -840,7 +839,7 @@ static void gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg) * is data. Keep to the MRU of the mux. This path handles the usual tty * interface which is a byte stream with optional modem data. * - * Caller must hold the tx_lock of the mux. + * Caller must hold the tx_mutex of the mux. */
static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci) @@ -903,7 +902,7 @@ static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci) * is data. Keep to the MRU of the mux. This path handles framed data * queued as skbuffs to the DLCI. * - * Caller must hold the tx_lock of the mux. + * Caller must hold the tx_mutex of the mux. */
static int gsm_dlci_data_output_framed(struct gsm_mux *gsm, @@ -919,7 +918,7 @@ static int gsm_dlci_data_output_framed(struct gsm_mux *gsm, if (dlci->adaption == 4) overhead = 1;
- /* dlci->skb is locked by tx_lock */ + /* dlci->skb is locked by tx_mutex */ if (dlci->skb == NULL) { dlci->skb = skb_dequeue_tail(&dlci->skb_list); if (dlci->skb == NULL) @@ -1019,13 +1018,12 @@ static void gsm_dlci_data_sweep(struct gsm_mux *gsm)
static void gsm_dlci_data_kick(struct gsm_dlci *dlci) { - unsigned long flags; int sweep;
if (dlci->constipated) return;
- spin_lock_irqsave(&dlci->gsm->tx_lock, flags); + mutex_lock(&dlci->gsm->tx_mutex); /* If we have nothing running then we need to fire up */ sweep = (dlci->gsm->tx_bytes < TX_THRESH_LO); if (dlci->gsm->tx_bytes == 0) { @@ -1036,7 +1034,7 @@ static void gsm_dlci_data_kick(struct gsm_dlci *dlci) } if (sweep) gsm_dlci_data_sweep(dlci->gsm); - spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags); + mutex_unlock(&dlci->gsm->tx_mutex); }
/* @@ -1258,7 +1256,6 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command, const u8 *data, int clen) { u8 buf[1]; - unsigned long flags;
switch (command) { case CMD_CLD: { @@ -1280,9 +1277,9 @@ static void gsm_control_message(struct gsm_mux *gsm, unsigned int command, gsm->constipated = false; gsm_control_reply(gsm, CMD_FCON, NULL, 0); /* Kick the link in case it is idling */ - spin_lock_irqsave(&gsm->tx_lock, flags); + mutex_lock(&gsm->tx_mutex); gsm_data_kick(gsm, NULL); - spin_unlock_irqrestore(&gsm->tx_lock, flags); + mutex_unlock(&gsm->tx_mutex); break; case CMD_FCOFF: /* Modem wants us to STFU */ @@ -2228,6 +2225,7 @@ static void gsm_free_mux(struct gsm_mux *gsm) break; } } + mutex_destroy(&gsm->tx_mutex); mutex_destroy(&gsm->mutex); kfree(gsm->txframe); kfree(gsm->buf); @@ -2299,12 +2297,12 @@ static struct gsm_mux *gsm_alloc_mux(void) } spin_lock_init(&gsm->lock); mutex_init(&gsm->mutex); + mutex_init(&gsm->tx_mutex); kref_init(&gsm->ref); INIT_LIST_HEAD(&gsm->tx_list); timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0); init_waitqueue_head(&gsm->event); spin_lock_init(&gsm->control_lock); - spin_lock_init(&gsm->tx_lock);
gsm->t1 = T1; gsm->t2 = T2; @@ -2329,6 +2327,7 @@ static struct gsm_mux *gsm_alloc_mux(void) } spin_unlock(&gsm_mux_lock); if (i == MAX_MUX) { + mutex_destroy(&gsm->tx_mutex); mutex_destroy(&gsm->mutex); kfree(gsm->txframe); kfree(gsm->buf); @@ -2653,16 +2652,15 @@ static int gsmld_open(struct tty_struct *tty) static void gsmld_write_wakeup(struct tty_struct *tty) { struct gsm_mux *gsm = tty->disc_data; - unsigned long flags;
/* Queue poll */ clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); - spin_lock_irqsave(&gsm->tx_lock, flags); + mutex_lock(&gsm->tx_mutex); gsm_data_kick(gsm, NULL); if (gsm->tx_bytes < TX_THRESH_LO) { gsm_dlci_data_sweep(gsm); } - spin_unlock_irqrestore(&gsm->tx_lock, flags); + mutex_unlock(&gsm->tx_mutex); }
/** @@ -2705,7 +2703,6 @@ static ssize_t gsmld_write(struct tty_struct *tty, struct file *file, const unsigned char *buf, size_t nr) { struct gsm_mux *gsm = tty->disc_data; - unsigned long flags; int space; int ret;
@@ -2713,13 +2710,13 @@ static ssize_t gsmld_write(struct tty_struct *tty, struct file *file, return -ENODEV;
ret = -ENOBUFS; - spin_lock_irqsave(&gsm->tx_lock, flags); + mutex_lock(&gsm->tx_mutex); space = tty_write_room(tty); if (space >= nr) ret = tty->ops->write(tty, buf, nr); else set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); - spin_unlock_irqrestore(&gsm->tx_lock, flags); + mutex_unlock(&gsm->tx_mutex);
return ret; }