Linux Kernel ‘uname()’ System Call Local Information Disclosure Vulnerability

Summary

The Linux kernel is prone to a local information-disclosure vulnerability.

Credit:

The information has been provided by Brad Spengler.
The original article can be found at: https://lkml.org/lkml/2012/10/9/550


Details

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

CVE Information:
CVE-2012-0957

Disclosure Timeline:
Published : Oct 09 2012
Updated : Oct 11 2012

Categories: News