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commit5a96b2d38dupstream. The compatibility ioctl wrapper for VCHIQ_IOC_AWAIT_COMPLETION assumes that the native ioctl always uses a message buffer and decrements msgbufcount. Certain message types do not use a message buffer and in this case msgbufcount is not decremented, and completion->header for the message is NULL. Because the wrapper unconditionally decrements msgbufcount, the calling process may assume that a message buffer has been used even when it has not. This results in a memory leak in the userspace code that interfaces with this driver. When msgbufcount is decremented, the userspace code assumes that the buffer can be freed though the reference in completion->header, which cannot happen when the reference is NULL. This patch causes the wrapper to only decrement msgbufcount when the native ioctl decrements it. Note that we cannot simply copy the native ioctl's value of msgbufcount, because the wrapper only retrieves messages from the native ioctl one at a time, while userspace may request multiple messages. See https://github.com/raspberrypi/linux/pull/2703 for more discussion of this patch. Fixes:5569a12609("staging: vchiq_arm: Add compatibility wrappers for ioctls") Signed-off-by: Ben Wolsieffer <benwolsieffer@gmail.com> Acked-by: Stefan Wahren <stefan.wahren@i2se.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.