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: 32dd59f96924 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/n_gsm.c | 53 +++++++++++++++++++++++----------------------------- 1 file changed, 24 insertions(+), 29 deletions(-)
--- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -248,7 +248,7 @@ struct gsm_mux { bool constipated; /* Asked by remote to shut up */ bool has_devices; /* Devices were registered */
- 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 @@ -680,7 +680,6 @@ static int gsm_send(struct gsm_mux *gsm, struct gsm_msg *msg; u8 *dp; int ocr; - unsigned long flags;
msg = gsm_data_alloc(gsm, addr, 0, control); if (!msg) @@ -702,10 +701,10 @@ static int gsm_send(struct gsm_mux *gsm,
gsm_print_packet("Q->", addr, cr, control, NULL, 0);
- spin_lock_irqsave(&gsm->tx_lock, flags); + mutex_lock(&gsm->tx_mutex); list_add_tail(&msg->list, &gsm->tx_ctrl_list); gsm->tx_bytes += msg->len; - spin_unlock_irqrestore(&gsm->tx_lock, flags); + mutex_unlock(&gsm->tx_mutex); gsmld_write_trigger(gsm);
return 0; @@ -730,7 +729,7 @@ static void gsm_dlci_clear_queues(struct spin_unlock_irqrestore(&dlci->lock, flags);
/* Clear data packets in MUX write queue */ - spin_lock_irqsave(&gsm->tx_lock, flags); + mutex_lock(&gsm->tx_mutex); list_for_each_entry_safe(msg, nmsg, &gsm->tx_data_list, list) { if (msg->addr != addr) continue; @@ -738,7 +737,7 @@ static void gsm_dlci_clear_queues(struct list_del(&msg->list); kfree(msg); } - spin_unlock_irqrestore(&gsm->tx_lock, flags); + mutex_unlock(&gsm->tx_mutex); }
/** @@ -1024,10 +1023,9 @@ static void __gsm_data_queue(struct gsm_
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); }
/** @@ -1039,7 +1037,7 @@ static void gsm_data_queue(struct gsm_dl * 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) @@ -1099,7 +1097,7 @@ static int gsm_dlci_data_output(struct g * 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, @@ -1115,7 +1113,7 @@ static int gsm_dlci_data_output_framed(s 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) @@ -1169,7 +1167,7 @@ static int gsm_dlci_data_output_framed(s * Push an empty frame in to the transmit queue to update the modem status * bits and to transmit an optional break. * - * Caller must hold the tx_lock of the mux. + * Caller must hold the tx_mutex of the mux. */
static int gsm_dlci_modem_output(struct gsm_mux *gsm, struct gsm_dlci *dlci, @@ -1283,13 +1281,12 @@ static int gsm_dlci_data_sweep(struct gs
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) { @@ -1300,7 +1297,7 @@ static void gsm_dlci_data_kick(struct gs } if (sweep) gsm_dlci_data_sweep(dlci->gsm); - spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags); + mutex_unlock(&dlci->gsm->tx_mutex); }
/* @@ -1994,14 +1991,13 @@ static void gsm_dlci_command(struct gsm_ static void gsm_kick_timeout(struct work_struct *work) { struct gsm_mux *gsm = container_of(work, struct gsm_mux, kick_timeout.work); - unsigned long flags; int sent = 0;
- spin_lock_irqsave(&gsm->tx_lock, flags); + mutex_lock(&gsm->tx_mutex); /* If we have nothing running then we need to fire up */ if (gsm->tx_bytes < TX_THRESH_LO) sent = gsm_dlci_data_sweep(gsm); - spin_unlock_irqrestore(&gsm->tx_lock, flags); + mutex_unlock(&gsm->tx_mutex);
if (sent && debug & 4) pr_info("%s TX queue stalled\n", __func__); @@ -2531,6 +2527,7 @@ static void gsm_free_mux(struct gsm_mux break; } } + mutex_destroy(&gsm->tx_mutex); mutex_destroy(&gsm->mutex); kfree(gsm->txframe); kfree(gsm->buf); @@ -2602,6 +2599,7 @@ static struct gsm_mux *gsm_alloc_mux(voi } spin_lock_init(&gsm->lock); mutex_init(&gsm->mutex); + mutex_init(&gsm->tx_mutex); kref_init(&gsm->ref); INIT_LIST_HEAD(&gsm->tx_ctrl_list); INIT_LIST_HEAD(&gsm->tx_data_list); @@ -2610,7 +2608,6 @@ static struct gsm_mux *gsm_alloc_mux(voi 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; @@ -2635,6 +2632,7 @@ static struct gsm_mux *gsm_alloc_mux(voi } spin_unlock(&gsm_mux_lock); if (i == MAX_MUX) { + mutex_destroy(&gsm->tx_mutex); mutex_destroy(&gsm->mutex); kfree(gsm->txframe); kfree(gsm->buf); @@ -2790,17 +2788,16 @@ static void gsmld_write_trigger(struct g static void gsmld_write_task(struct work_struct *work) { struct gsm_mux *gsm = container_of(work, struct gsm_mux, tx_work); - unsigned long flags; int i, ret;
/* All outstanding control channel and control messages and one data * frame is sent. */ ret = -ENODEV; - spin_lock_irqsave(&gsm->tx_lock, flags); + mutex_lock(&gsm->tx_mutex); if (gsm->tty) ret = gsm_data_kick(gsm); - spin_unlock_irqrestore(&gsm->tx_lock, flags); + mutex_unlock(&gsm->tx_mutex);
if (ret >= 0) for (i = 0; i < NUM_DLCI; i++) @@ -3008,7 +3005,6 @@ static ssize_t gsmld_write(struct tty_st const unsigned char *buf, size_t nr) { struct gsm_mux *gsm = tty->disc_data; - unsigned long flags; int space; int ret;
@@ -3016,13 +3012,13 @@ static ssize_t gsmld_write(struct tty_st 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; } @@ -3319,14 +3315,13 @@ static struct tty_ldisc_ops tty_ldisc_pa static void gsm_modem_upd_via_data(struct gsm_dlci *dlci, u8 brk) { struct gsm_mux *gsm = dlci->gsm; - unsigned long flags;
if (dlci->state != DLCI_OPEN || dlci->adaption != 2) return;
- spin_lock_irqsave(&gsm->tx_lock, flags); + mutex_lock(&gsm->tx_mutex); gsm_dlci_modem_output(gsm, dlci, brk); - spin_unlock_irqrestore(&gsm->tx_lock, flags); + mutex_unlock(&gsm->tx_mutex); }
/**