kernel/sys.c: fix stack memory content leak via UNAME26 (2702b152) · Commits · 戴 / test

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:

PaX Team <pageexec@freemail.hu> Signed-off-by:

Kees 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:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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;
		}

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