6.6-stable review patch. If anyone has any objections, please let me know.
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From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp
[ Upstream commit eecd203ada43a4693ce6fdd3a58ae10c7819252c ]
syzbot is reporting that imon has three problems which result in hung tasks due to forever holding device lock [1].
First problem is that when usb_rx_callback_intf0() once got -EPROTO error after ictx->dev_present_intf0 became true, usb_rx_callback_intf0() resubmits urb after printk(), and resubmitted urb causes usb_rx_callback_intf0() to again get -EPROTO error. This results in printk() flooding (RCU stalls).
Alan Stern commented [2] that
In theory it's okay to resubmit _if_ the driver has a robust error-recovery scheme (such as giving up after some fixed limit on the number of errors or after some fixed time has elapsed, perhaps with a time delay to prevent a flood of errors). Most drivers don't bother to do this; they simply give up right away. This makes them more vulnerable to short-term noise interference during USB transfers, but in reality such interference is quite rare. There's nothing really wrong with giving up right away.
but imon has a poor error-recovery scheme which just retries forever; this behavior should be fixed.
Since I'm not sure whether it is safe for imon users to give up upon any error code, this patch takes care of only union of error codes chosen from modules in drivers/media/rc/ directory which handle -EPROTO error (i.e. ir_toy, mceusb and igorplugusb).
Second problem is that when usb_rx_callback_intf0() once got -EPROTO error before ictx->dev_present_intf0 becomes true, usb_rx_callback_intf0() always resubmits urb due to commit 8791d63af0cf ("[media] imon: don't wedge hardware after early callbacks"). Move the ictx->dev_present_intf0 test introduced by commit 6f6b90c9231a ("[media] imon: don't parse scancodes until intf configured") to immediately before imon_incoming_packet(), or the first problem explained above happens without printk() flooding (i.e. hung task).
Third problem is that when usb_rx_callback_intf0() is not called for some reason (e.g. flaky hardware; the reproducer for this problem sometimes prevents usb_rx_callback_intf0() from being called), wait_for_completion_interruptible() in send_packet() never returns (i.e. hung task). As a workaround for such situation, change send_packet() to wait for completion with timeout of 10 seconds.
Link: https://syzkaller.appspot.com/bug?extid=592e2ab8775dbe0bf09a [1] Link: https://lkml.kernel.org/r/d6da6709-d799-4be3-a695-850bddd6eb24@rowland.harva... [2] Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: Sean Young sean@mess.org Signed-off-by: Hans Verkuil hverkuil+cisco@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/media/rc/imon.c | 61 +++++++++++++++++++++++++---------------- 1 file changed, 37 insertions(+), 24 deletions(-)
diff --git a/drivers/media/rc/imon.c b/drivers/media/rc/imon.c index f4deca8894e0f..bb4aabb08c06e 100644 --- a/drivers/media/rc/imon.c +++ b/drivers/media/rc/imon.c @@ -650,12 +650,15 @@ static int send_packet(struct imon_context *ictx) smp_rmb(); /* ensure later readers know we're not busy */ pr_err_ratelimited("error submitting urb(%d)\n", retval); } else { - /* Wait for transmission to complete (or abort) */ - retval = wait_for_completion_interruptible( - &ictx->tx.finished); - if (retval) { + /* Wait for transmission to complete (or abort or timeout) */ + retval = wait_for_completion_interruptible_timeout(&ictx->tx.finished, 10 * HZ); + if (retval <= 0) { usb_kill_urb(ictx->tx_urb); pr_err_ratelimited("task interrupted\n"); + if (retval < 0) + ictx->tx.status = retval; + else + ictx->tx.status = -ETIMEDOUT; }
ictx->tx.busy = false; @@ -1754,14 +1757,6 @@ static void usb_rx_callback_intf0(struct urb *urb) if (!ictx) return;
- /* - * if we get a callback before we're done configuring the hardware, we - * can't yet process the data, as there's nowhere to send it, but we - * still need to submit a new rx URB to avoid wedging the hardware - */ - if (!ictx->dev_present_intf0) - goto out; - switch (urb->status) { case -ENOENT: /* usbcore unlink successful! */ return; @@ -1770,16 +1765,29 @@ static void usb_rx_callback_intf0(struct urb *urb) break;
case 0: - imon_incoming_packet(ictx, urb, intfnum); + /* + * if we get a callback before we're done configuring the hardware, we + * can't yet process the data, as there's nowhere to send it, but we + * still need to submit a new rx URB to avoid wedging the hardware + */ + if (ictx->dev_present_intf0) + imon_incoming_packet(ictx, urb, intfnum); break;
+ case -ECONNRESET: + case -EILSEQ: + case -EPROTO: + case -EPIPE: + dev_warn(ictx->dev, "imon %s: status(%d)\n", + __func__, urb->status); + return; + default: dev_warn(ictx->dev, "imon %s: status(%d): ignored\n", __func__, urb->status); break; }
-out: usb_submit_urb(ictx->rx_urb_intf0, GFP_ATOMIC); }
@@ -1795,14 +1803,6 @@ static void usb_rx_callback_intf1(struct urb *urb) if (!ictx) return;
- /* - * if we get a callback before we're done configuring the hardware, we - * can't yet process the data, as there's nowhere to send it, but we - * still need to submit a new rx URB to avoid wedging the hardware - */ - if (!ictx->dev_present_intf1) - goto out; - switch (urb->status) { case -ENOENT: /* usbcore unlink successful! */ return; @@ -1811,16 +1811,29 @@ static void usb_rx_callback_intf1(struct urb *urb) break;
case 0: - imon_incoming_packet(ictx, urb, intfnum); + /* + * if we get a callback before we're done configuring the hardware, we + * can't yet process the data, as there's nowhere to send it, but we + * still need to submit a new rx URB to avoid wedging the hardware + */ + if (ictx->dev_present_intf1) + imon_incoming_packet(ictx, urb, intfnum); break;
+ case -ECONNRESET: + case -EILSEQ: + case -EPROTO: + case -EPIPE: + dev_warn(ictx->dev, "imon %s: status(%d)\n", + __func__, urb->status); + return; + default: dev_warn(ictx->dev, "imon %s: status(%d): ignored\n", __func__, urb->status); break; }
-out: usb_submit_urb(ictx->rx_urb_intf1, GFP_ATOMIC); }