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5a23699a39
The patch "ALSA: control: code refactoring for ELEM_READ/ELEM_WRITE
operations" introduced a potential for kernel memory corruption due
to an incorrect if statement allowing non-readable controls to fall
through and call the get function. For TLV controls a driver can omit
SNDRV_CTL_ELEM_ACCESS_READ to ensure that only the TLV get function
can be called. Instead the normal get() can be invoked unexpectedly
and as the driver expects that this will only be called for controls
<= 512 bytes, potentially try to copy >512 bytes into the 512 byte
return array, so corrupting kernel memory.
The problem is an attempt to refactor the snd_ctl_elem_read function
to invert the logic so that it conditionally aborted if the control
is unreadable instead of conditionally executing. But the if statement
wasn't inverted correctly.
The correct inversion of
if (a && !b)
is
if (!a || b)
Fixes: becf9e5d553c2 ("ALSA: control: code refactoring for ELEM_READ/ELEM_WRITE operations")
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.