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usb: cdc_acm: prevent race at write to acm while system resumes

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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: Dominik Bozek <dominikx.bozek@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dominik Bozek 2018-02-15 21:27:48 -08:00 committed by Greg Kroah-Hartman
parent 7a1646d922
commit b86b8eb6fe
1 changed files with 6 additions and 3 deletions
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9
drivers/usb/class/cdc-acm.c
View File

@ -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;