From: Raphael S. Carvalho Date: Thu, 9 Oct 2014 00:46:07 +0000 (-0300) Subject: blkdiscard: fix underflow when offset is greater than device size X-Git-Tag: v2.26-rc1~316 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=303884a4955db8b00d0eecf3b59a8c70895897b8;p=thirdparty%2Futil-linux.git blkdiscard: fix underflow when offset is greater than device size If offset (range[0]) is greater than device size (blksize), the variable 'end' will be greater than blksize, and range[1] (length) will be recalculated. The underflow happens when subtracting range[0] (offset) from blksize, thus range[1] will be the result of an underflow. The bug leads to unwanted behavior from the program, where range[1] is likely to be a high number and then will discard a considerable amount of blocks from the device. The fix consists of exitting the program with an error message when the condition stated above is true. Spotted while auditing the code. Signed-off-by: Raphael S. Carvalho --- diff --git a/sys-utils/blkdiscard.c b/sys-utils/blkdiscard.c index 2ddcdb1b46..2f22af7249 100644 --- a/sys-utils/blkdiscard.c +++ b/sys-utils/blkdiscard.c @@ -149,6 +149,8 @@ int main(int argc, char **argv) range[1] &= ~(secsize - 1); /* is the range end behind the end of the device ?*/ + if (range[0] > blksize) + err(EXIT_FAILURE, _("%s: offset is greater than device size"), path); end = range[0] + range[1]; if (end < range[0] || end > blksize) range[1] = blksize - range[0];