This is a note to let you know that I've just added the patch titled
USB: cdc-acm: untangle a circular dependency between callback and
to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 6069e3e927c8fb3a1947b07d1a561644ea960248 Mon Sep 17 00:00:00 2001
From: Oliver Neukum oneukum@suse.com Date: Thu, 11 Mar 2021 14:01:25 +0100 Subject: USB: cdc-acm: untangle a circular dependency between callback and softint
We have a cycle of callbacks scheduling works which submit URBs with thos callbacks. This needs to be blocked, stopped and unblocked to untangle the circle.
The issue leads to faults like:
[ 55.068392] Unable to handle kernel paging request at virtual address 6b6b6c03 [ 55.075624] pgd = be866494 [ 55.078335] [6b6b6c03] *pgd=00000000 [ 55.081924] Internal error: Oops: 5 [#1] PREEMPT SMP ARM [ 55.087238] Modules linked in: ppp_async crc_ccitt ppp_generic slhc xt_TCPMSS xt_tcpmss xt_hl nf_log_ipv6 nf_log_ipv4 nf_log_common xt_policy xt_limit xt_conntrack xt_tcpudp xt_pkttype ip6table_mangle iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 iptable_mangle ip6table_filter ip6_tables iptable_filter ip_tables des_generic md5 sch_fq_codel cdc_mbim cdc_wdm cdc_ncm usbnet mii cdc_acm usb_storage ip_tunnel xfrm_user xfrm6_tunnel tunnel6 xfrm4_tunnel tunnel4 esp6 esp4 ah6 ah4 xfrm_algo xt_LOG xt_LED xt_comment x_tables ipv6 [ 55.134954] CPU: 0 PID: 82 Comm: kworker/0:2 Tainted: G T 5.8.17 #1 [ 55.142526] Hardware name: Freescale i.MX7 Dual (Device Tree) [ 55.148304] Workqueue: events acm_softint [cdc_acm] [ 55.153196] PC is at kobject_get+0x10/0xa4 [ 55.157302] LR is at usb_get_dev+0x14/0x1c [ 55.161402] pc : [<8047c06c>] lr : [<80560448>] psr: 20000193 [ 55.167671] sp : bca39ea8 ip : 00007374 fp : bf6cbd80 [ 55.172899] r10: 00000000 r9 : bdd92284 r8 : bdd92008 [ 55.178128] r7 : 6b6b6b6b r6 : fffffffe r5 : 60000113 r4 : 6b6b6be3 [ 55.184658] r3 : 6b6b6b6b r2 : 00000111 r1 : 00000000 r0 : 6b6b6be3 [ 55.191191] Flags: nzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none [ 55.198417] Control: 10c5387d Table: bcf0c06a DAC: 00000051 [ 55.204168] Process kworker/0:2 (pid: 82, stack limit = 0x9bdd2a89) [ 55.210439] Stack: (0xbca39ea8 to 0xbca3a000) [ 55.214805] 9ea0: bf6cbd80 80769a50 6b6b6b6b 80560448 bdeb0500 8056bfe8 [ 55.222991] 9ec0: 00000002 b76da000 00000000 bdeb0500 bdd92448 bca38000 bdeb0510 8056d69c [ 55.231177] 9ee0: bca38000 00000000 80c050fc 00000000 bca39f44 09d42015 00000000 00000001 [ 55.239363] 9f00: bdd92448 bdd92438 bdd92000 7f1158c4 bdd92448 bca2ee00 bf6cbd80 bf6cef00 [ 55.247549] 9f20: 00000000 00000000 00000000 801412d8 bf6cbd98 80c03d00 bca2ee00 bf6cbd80 [ 55.255735] 9f40: bca2ee14 bf6cbd98 80c03d00 00000008 bca38000 80141568 00000000 80c446ae [ 55.263921] 9f60: 00000000 bc9ed880 bc9f0700 bca38000 bc117eb4 80141524 bca2ee00 bc9ed8a4 [ 55.272107] 9f80: 00000000 80147cc8 00000000 bc9f0700 80147b84 00000000 00000000 00000000 [ 55.280292] 9fa0: 00000000 00000000 00000000 80100148 00000000 00000000 00000000 00000000 [ 55.288477] 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 [ 55.296662] 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000 [ 55.304860] [<8047c06c>] (kobject_get) from [<80560448>] (usb_get_dev+0x14/0x1c) [ 55.312271] [<80560448>] (usb_get_dev) from [<8056bfe8>] (usb_hcd_unlink_urb+0x50/0xd8) [ 55.320286] [<8056bfe8>] (usb_hcd_unlink_urb) from [<8056d69c>] (usb_kill_urb.part.0+0x44/0xd0) [ 55.329004] [<8056d69c>] (usb_kill_urb.part.0) from [<7f1158c4>] (acm_softint+0x4c/0x10c [cdc_acm]) [ 55.338082] [<7f1158c4>] (acm_softint [cdc_acm]) from [<801412d8>] (process_one_work+0x19c/0x3e8) [ 55.346969] [<801412d8>] (process_one_work) from [<80141568>] (worker_thread+0x44/0x4dc) [ 55.355072] [<80141568>] (worker_thread) from [<80147cc8>] (kthread+0x144/0x180) [ 55.362481] [<80147cc8>] (kthread) from [<80100148>] (ret_from_fork+0x14/0x2c) [ 55.369706] Exception stack(0xbca39fb0 to 0xbca39ff8)
Tested-by: Bruno Thomsen bruno.thomsen@gmail.com Signed-off-by: Oliver Neukum oneukum@suse.com Cc: stable stable@vger.kernel.org Link: https://lore.kernel.org/r/20210311130126.15972-1-oneukum@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/class/cdc-acm.c | 48 ++++++++++++++++++++++++------------- 1 file changed, 32 insertions(+), 16 deletions(-)
diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c index b013671261a2..d684cf94b1c0 100644 --- a/drivers/usb/class/cdc-acm.c +++ b/drivers/usb/class/cdc-acm.c @@ -147,17 +147,29 @@ static inline int acm_set_control(struct acm *acm, int control) #define acm_send_break(acm, ms) \ acm_ctrl_msg(acm, USB_CDC_REQ_SEND_BREAK, ms, NULL, 0)
-static void acm_kill_urbs(struct acm *acm) +static void acm_poison_urbs(struct acm *acm) { int i;
- usb_kill_urb(acm->ctrlurb); + usb_poison_urb(acm->ctrlurb); for (i = 0; i < ACM_NW; i++) - usb_kill_urb(acm->wb[i].urb); + usb_poison_urb(acm->wb[i].urb); for (i = 0; i < acm->rx_buflimit; i++) - usb_kill_urb(acm->read_urbs[i]); + usb_poison_urb(acm->read_urbs[i]); +} + +static void acm_unpoison_urbs(struct acm *acm) +{ + int i; + + for (i = 0; i < acm->rx_buflimit; i++) + usb_unpoison_urb(acm->read_urbs[i]); + for (i = 0; i < ACM_NW; i++) + usb_unpoison_urb(acm->wb[i].urb); + usb_unpoison_urb(acm->ctrlurb); }
+ /* * Write buffer management. * All of these assume proper locks taken by the caller. @@ -226,9 +238,10 @@ static int acm_start_wb(struct acm *acm, struct acm_wb *wb)
rc = usb_submit_urb(wb->urb, GFP_ATOMIC); if (rc < 0) { - dev_err(&acm->data->dev, - "%s - usb_submit_urb(write bulk) failed: %d\n", - __func__, rc); + if (rc != -EPERM) + dev_err(&acm->data->dev, + "%s - usb_submit_urb(write bulk) failed: %d\n", + __func__, rc); acm_write_done(acm, wb); } return rc; @@ -482,11 +495,6 @@ static void acm_read_bulk_callback(struct urb *urb) dev_vdbg(&acm->data->dev, "got urb %d, len %d, status %d\n", rb->index, urb->actual_length, status);
- if (!acm->dev) { - dev_dbg(&acm->data->dev, "%s - disconnected\n", __func__); - return; - } - switch (status) { case 0: usb_mark_last_busy(acm->dev); @@ -733,6 +741,7 @@ static void acm_port_shutdown(struct tty_port *port) * Need to grab write_lock to prevent race with resume, but no need to * hold it due to the tty-port initialised flag. */ + acm_poison_urbs(acm); spin_lock_irq(&acm->write_lock); spin_unlock_irq(&acm->write_lock);
@@ -749,7 +758,8 @@ static void acm_port_shutdown(struct tty_port *port) usb_autopm_put_interface_async(acm->control); }
- acm_kill_urbs(acm); + acm_unpoison_urbs(acm); + }
static void acm_tty_cleanup(struct tty_struct *tty) @@ -1542,8 +1552,14 @@ static void acm_disconnect(struct usb_interface *intf) if (!acm) return;
- mutex_lock(&acm->mutex); acm->disconnected = true; + /* + * there is a circular dependency. acm_softint() can resubmit + * the URBs in error handling so we need to block any + * submission right away + */ + acm_poison_urbs(acm); + mutex_lock(&acm->mutex); if (acm->country_codes) { device_remove_file(&acm->control->dev, &dev_attr_wCountryCodes); @@ -1562,7 +1578,6 @@ static void acm_disconnect(struct usb_interface *intf) tty_kref_put(tty); }
- acm_kill_urbs(acm); cancel_delayed_work_sync(&acm->dwork);
tty_unregister_device(acm_tty_driver, acm->minor); @@ -1604,7 +1619,7 @@ static int acm_suspend(struct usb_interface *intf, pm_message_t message) if (cnt) return 0;
- acm_kill_urbs(acm); + acm_poison_urbs(acm); cancel_delayed_work_sync(&acm->dwork); acm->urbs_in_error_delay = 0;
@@ -1617,6 +1632,7 @@ static int acm_resume(struct usb_interface *intf) struct urb *urb; int rv = 0;
+ acm_unpoison_urbs(acm); spin_lock_irq(&acm->write_lock);
if (--acm->susp_count)