Vulnerable Systems:
* Linux kernel 3.2.13 and prior
Calling uname() with the UNAME26 personality set allows a leak of kernel stack contents. This fixes it by initializing the stack buffer to zero, defensively calculating the length of copy_to_user() call, and making the len argument unsigned.
---
kernel/sys.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/kernel/sys.c b/kernel/sys.c
index c5cb5b9..6329092 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1265,13 +1265,13 @@ 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];
+ char buf[65] = { 0 };
+ const char *rest = UTS_RELEASE;
if (current->personality & UNAME26) {
- char *rest = UTS_RELEASE;
int ndots = 0;
unsigned v;
@@ -1283,7 +1283,9 @@ 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);
+ snprintf(buf, sizeof(buf), "2.6.%u%s", v, rest);
+ if (sizeof(buf) < len)
+ len = sizeof(buf);
ret = copy_to_user(release, buf, len);
}
return ret;
--
1.7.9.5
