From: Dominik Bozek <dominikx.bozek@xxxxxxxxx>
ACM driver may accept data to transmit while system is not fully
resumed. In this case ACM driver buffers data and prepare URBs
on usb anchor list.
There is a little chance that two tasks put a char and initiate
acm_tty_flush_chars(). In such a case, driver will put one URB
twice on usb anchor list.
This patch also reset length of data before resue of a buffer.
This not only prevent sending rubbish, but also lower risc of race.
Without this patch we hit following kernel panic in one of our
stabilty/stress tests.
[ 46.884442] *list_add double add*: new=ffff9b2ab7289330, prev=ffff9b2ab7289330, next=ffff9b2ab81e28e0.
[ 46.884476] Modules linked in: hci_uart btbcm bluetooth rfkill_gpio igb_avb(O) cfg80211 snd_soc_sst_bxt_tdf8532 snd_soc_skl snd_soc_skl_ipc snd_soc_sst_ipc snd_soc_sst_dsp snd_soc_sst_acpi snd_soc_sst_match snd_hda_ext_core snd_hda_core trusty_timer trusty_wall trusty_log trusty_virtio trusty_ipc trusty_mem trusty_irq trusty virtio_ring virtio intel_ipu4_mmu_bxtB0 lib2600_mod_bxtB0 intel_ipu4_isys_mod_bxtB0 lib2600psys_mod_bxtB0 intel_ipu4_psys_mod_bxtB0 intel_ipu4_mod_bxtB0 intel_ipu4_wrapper_bxtB0 intel_ipu4_acpi videobuf2_dma_contig as3638 dw9714 lm3643 crlmodule smiapp smiapp_pll
[ 46.884480] CPU: 1 PID: 33 Comm: kworker/u8:1 Tainted: G U W O 4.9.56-quilt-2e5dc0ac-g618ed69ced6e-dirty #4
[ 46.884489] Workqueue: events_unbound flush_to_ldisc
[ 46.884494] ffffb98ac012bb08 ffffffffad3e82e5 ffffb98ac012bb58 0000000000000000
[ 46.884497] ffffb98ac012bb48 ffffffffad0a23d1 00000024ad6374dd ffff9b2ab7289330
[ 46.884500] ffff9b2ab81e28e0 ffff9b2ab7289330 0000000000000002 0000000000000000
[ 46.884501] Call Trace:
[ 46.884507] [<ffffffffad3e82e5>] dump_stack+0x67/0x92
[ 46.884511] [<ffffffffad0a23d1>] __warn+0xd1/0xf0
[ 46.884513] [<ffffffffad0a244f>] warn_slowpath_fmt+0x5f/0x80
[ 46.884516] [<ffffffffad407443>] __list_add+0xb3/0xc0
[ 46.884521] [<ffffffffad71133c>] *usb_anchor_urb*+0x4c/0xa0
[ 46.884524] [<ffffffffad782c6f>] *acm_tty_flush_chars*+0x8f/0xb0
[ 46.884527] [<ffffffffad782cd1>] *acm_tty_put_char*+0x41/0x100
[ 46.884530] [<ffffffffad4ced34>] tty_put_char+0x24/0x40
[ 46.884533] [<ffffffffad4d3bf5>] do_output_char+0xa5/0x200
[ 46.884535] [<ffffffffad4d3e98>] __process_echoes+0x148/0x290
[ 46.884538] [<ffffffffad4d654c>] n_tty_receive_buf_common+0x57c/0xb00
[ 46.884541] [<ffffffffad4d6ae4>] n_tty_receive_buf2+0x14/0x20
[ 46.884543] [<ffffffffad4d9662>] tty_ldisc_receive_buf+0x22/0x50
[ 46.884545] [<ffffffffad4d9c05>] flush_to_ldisc+0xc5/0xe0
[ 46.884549] [<ffffffffad0bcfe8>] process_one_work+0x148/0x440
[ 46.884551] [<ffffffffad0bdc19>] worker_thread+0x69/0x4a0
[ 46.884554] [<ffffffffad0bdbb0>] ? max_active_store+0x80/0x80
[ 46.884556] [<ffffffffad0c2e10>] kthread+0x110/0x130
[ 46.884559] [<ffffffffad0c2d00>] ? kthread_park+0x60/0x60
[ 46.884563] [<ffffffffadad9917>] ret_from_fork+0x27/0x40
[ 46.884566] ---[ end trace 3bd599058b8a9eb3 ]---
Signed-off-by: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@xxxxxxxxx>
---
drivers/usb/class/cdc-acm.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 8e0636c963a7..f2b351100b9f 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -174,6 +174,7 @@ static int acm_wb_alloc(struct acm *acm)
wb = &acm->wb[wbn];
if (!wb->use) {
wb->use = 1;
+ wb->len = 0;
return wbn;
}
wbn = (wbn + 1) % ACM_NW;
@@ -805,16 +806,18 @@ static int acm_tty_write(struct tty_struct *tty,
static void acm_tty_flush_chars(struct tty_struct *tty)
{
struct acm *acm = tty->driver_data;
- struct acm_wb *cur = acm->putbuffer;
+ struct acm_wb *cur;
int err;
unsigned long flags;
+ spin_lock_irqsave(&acm->write_lock, flags);
+
+ cur = acm->putbuffer;
if (!cur) /* nothing to do */
- return;
+ goto out;
acm->putbuffer = NULL;
err = usb_autopm_get_interface_async(acm->control);
- spin_lock_irqsave(&acm->write_lock, flags);
if (err < 0) {
cur->use = 0;
acm->putbuffer = cur;
--
2.7.4
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