CVE-2025-68194

In the Linux kernel, the following vulnerability has been resolved:

media: imon: make send_packet() more robust

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 usbrxcallbackintf0() once got -EPROTO error after ictx->devpresentintf0 became true, usbrxcallbackintf0() resubmits urb after printk(), and resubmitted urb causes usbrxcallback_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 usbrxcallbackintf0() once got -EPROTO error before ictx->devpresentintf0 becomes true, usbrxcallbackintf0() always resubmits urb due to commit 8791d63af0cf ("[media] imon: don't wedge hardware after early callbacks"). Move the ictx->devpresentintf0 test introduced by commit 6f6b90c9231a ("[media] imon: don't parse scancodes until intf configured") to immediately before imonincomingpacket(), or the first problem explained above happens without printk() flooding (i.e. hung task).

Third problem is that when usbrxcallbackintf0() is not called for some reason (e.g. flaky hardware; the reproducer for this problem sometimes prevents usbrxcallbackintf0() from being called), waitforcompletioninterruptible() in sendpacket() never returns (i.e. hung task). As a workaround for such situation, change send_packet() to wait for completion with timeout of 10 seconds.