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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-09-22 09:34:56 +02:00
Baul Lee
29a4c29943
commit0970274613upstream. snd_usbmidi_akai_output() computes its fill-loop bound buf_end = ep->max_transfer - MAX_AKAI_SYSEX_LEN - 1; as a signed int, so a small device-advertised bulk-OUT max_transfer makes buf_end negative. The loop guard then compares the u32 urb->transfer_buffer_length against that negative int: the usual arithmetic conversion turns buf_end into a large unsigned value, so the guard stays true and each iteration keeps appending SysEx framing and payload bytes past the end of the URB transfer buffer, which is only max_transfer bytes long. A USB device that advertises a tiny bulk-OUT endpoint can therefore trigger an attacker-length- and content-controlled heap out-of-bounds write when a process writes to the created /dev/snd/midiC*D* node. Return early when there is no room for even one SysEx, so the loop is never entered with a bound that would wrap. The loop is the last statement of the function, so bailing out is equivalent to it not running. Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com> Fixes:4434ade8c9("ALSA: usb-audio: add support for Akai MPD16") Suggested-by: Takashi Iwai <tiwai@suse.de> Reported-by: Federico Kirschbaum <federico.kirschbaum@xbow.com> Reported-by: Baul Lee <baul.lee@xbow.com> Cc: stable@vger.kernel.org Signed-off-by: Baul Lee <baul.lee@xbow.com> Link: https://patch.msgid.link/20260726074500.50145-1-baul.lee@xbow.com Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.