tree 4df0cde1032194307226781e6980384d03d3e280
parent e4a16ea22fd96fd2545fb9d403f7e8d31c9fc04a
author Alexander Larkin <avlarkin82@gmail.com> 1625463576 -0700
committer COS Cherry Picker <cloud-image-release@prod.google.com> 1626895545 -0700

Input: joydev - prevent use of not validated data in JSIOCSBTNMAP ioctl

Even though we validate user-provided inputs we then traverse past
validated data when applying the new map. The issue was originally
discovered by Murray McAllister with this simple POC (if the following
is executed by an unprivileged user it will instantly panic the system):

int main(void) {
	int fd, ret;
	unsigned int buffer[10000];

	fd = open("/dev/input/js0", O_RDONLY);
	if (fd == -1)
		printf("Error opening file\n");

	ret = ioctl(fd, JSIOCSBTNMAP & ~IOCSIZE_MASK, &buffer);
	printf("%d\n", ret);
}

The solution is to traverse internal buffer which is guaranteed to only
contain valid date when constructing the map.

BUG=b/193628549
TEST=presubmit
SOURCE=UPSTREAM(f8f84af5da9ee04ef1d271528656dac42a090d00)
RELEASE_NOTE=Fix CVE-2021-3612

cos-patch: security-high
Fixes: 182d679b2298 ("Input: joydev - prevent potential read overflow in ioctl")
Fixes: 999b874f4aa3 ("Input: joydev - validate axis/button maps before clobbering current ones")
Reported-by: Murray McAllister <murray.mcallister@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Alexander Larkin <avlarkin82@gmail.com>
Link: https://lore.kernel.org/r/20210620120030.1513655-1-avlarkin82@gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Change-Id: I08bedd8bab51fd174e603ceeca3370bcb9bb1345
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/19612
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Roy Yang <royyang@google.com>
Tested-by: Oleksandr Tymoshenko <ovt@google.com>