[PATCH 0/1][SRU][X] Bad posix clock speculation mitigation backport (LP: #1847189)

[Tyler Hicks]

BugLink: https://launchpad.net/bugs/1847189

[Impact]

Vitaly Nikolenko pointed out that syscall(__NR_clock_gettime, 10, 0) can
be used to perform a denial of service (system crash) or possibly
execute arbitrary code in the Ubuntu Xenial kernel:

  https://twitter.com/vnik5287/status/1180666151216435200

[Test Case]

Execute the following test program and verify that it prints out
"clock_gettime: Invalid argument" rather than triggering a NULL pointer
dereference and stack trace in the kernel logs.

==========
#include <stdio.h>
#include <time.h>

int main(void)
{
        int rc = clock_gettime(10, 0);

        if (rc < 0)
                perror("clock_gettime");

        return rc;
}
==========

[Regression Potential]

Low. The fix is easy to review and fixes a denial of service issue
that's trivial to trigger.

Tyler

Tyler Hicks (1):
  UBUNTU: SAUCE: Fix posix clock speculation mitigation backport

 kernel/time/posix-timers.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

-- 
2.17.1