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Commit 2702b152 authored by Kees Cook's avatar Kees Cook Committed by Linus Torvalds
Browse files

kernel/sys.c: fix stack memory content leak via UNAME26 



Calling uname() with the UNAME26 personality set allows a leak of kernel
stack contents.  This fixes it by defensively calculating the length of
copy_to_user() call, making the len argument unsigned, and initializing
the stack buffer to zero (now technically unneeded, but hey, overkill).

CVE-2012-0957

Reported-by: default avatarPaX Team <pageexec@freemail.hu>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1d46e232

kernel/sys.c

+7 −5
Original line number Diff line number Diff line
@@ -1265,15 +1265,16 @@ DECLARE_RWSEM(uts_sem); 
 * Work around broken programs that cannot handle "Linux 3.0".

 * Instead we map 3.x to 2.6.40+x, so e.g. 3.0 would be 2.6.40

 */

static int override_release(char __user *release, int len)

static int override_release(char __user *release, size_t len)

{

	int ret = 0;

	char buf[65];



	if (current->personality & UNAME26) {

		char *rest = UTS_RELEASE;

		const char *rest = UTS_RELEASE;

		char buf[65] = { 0 };

		int ndots = 0;

		unsigned v;

		size_t copy;



		while (*rest) {

			if (*rest == '.' && ++ndots >= 3)
@@ -1283,8 +1284,9 @@ static int override_release(char __user *release, int len) 
			rest++;

		}

		v = ((LINUX_VERSION_CODE >> 8) & 0xff) + 40;

		snprintf(buf, len, "2.6.%u%s", v, rest);

		ret = copy_to_user(release, buf, len);

		copy = min(sizeof(buf), max_t(size_t, 1, len));

		copy = scnprintf(buf, copy, "2.6.%u%s", v, rest);

		ret = copy_to_user(release, buf, copy + 1);

	}

	return ret;

}