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

[Andrea Righi]

On Tue, Oct 08, 2019 at 06:10:14AM +0000, Tyler Hicks wrote:
> 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(-)

The fix makes sense to me.

Acked-by: Andrea Righi <andrea.righi at canonical.com>