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Filename Latest commit message Latest commit date
Tetsuo Handa 519737af11 media: imon: make send_packet() more robust
[ 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 8791d63af0 ("[media] imon: don't wedge
hardware after early callbacks"). Move the ictx->dev_present_intf0 test
introduced by commit 6f6b90c923 ("[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.harvard.edu [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>
2025-12-03 12:45:09 +01:00
arch powerpc/eeh: Use result of error_detected() in uevent 2025-12-03 12:45:09 +01:00
block block: use int to store blk_stack_limits() return value 2025-10-29 13:59:46 +01:00
certs
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-29 13:59:52 +01:00
Documentation arm64: errata: Apply workarounds for Neoverse-V3AE 2025-10-29 14:00:00 +01:00
drivers media: imon: make send_packet() more robust 2025-12-03 12:45:09 +01:00
fs btrfs: use smp_mb__after_atomic() when forcing COW in create_pending_snapshot() 2025-12-03 12:45:04 +01:00
include bpf: Don't use %pK through printk 2025-12-03 12:45:06 +01:00
init
ipc
kernel uprobe: Do not emulate/sstep original instruction when ip is changed 2025-12-03 12:45:08 +01:00
lib lib/genalloc: fix device leak in of_gen_pool_get() 2025-10-29 13:59:53 +01:00
LICENSES
mm mm: hugetlb: avoid soft lockup when mprotect to large memory area 2025-10-29 13:59:50 +01:00
net net: ipv6: fix field-spanning memcpy warning in AH output 2025-12-03 12:45:09 +01:00
samples
scripts
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-29 14:00:01 +01:00
sound ASoC: qdsp6: q6asm: do not sleep while atomic 2025-12-03 12:45:05 +01:00
tools selftests/net: Ensure assert() triggers in psock_tpacket.c 2025-12-03 12:45:09 +01:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile Linux 5.4.301 2025-10-29 14:00:02 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.