Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fix from Ingo Molnar:
 "Make posix clock ID usage Spectre-safe"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  posix-timers: Protect posix clock array access against speculation

1 files changed, 8 insertions, 3 deletions

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 75043046914e..10b7186d0638 100644
--- a/kernel/time/posix-timers.c
+++ b/kernel/time/posix-timers.c
@@ -50,6 +50,7 @@
 #include <linux/export.h>
 #include <linux/hashtable.h>
 #include <linux/compat.h>
+#include <linux/nospec.h>
 
 #include "timekeeping.h"
 #include "posix-timers.h"
@@ -1346,11 +1347,15 @@ static const struct k_clock * const posix_clocks[] = {
 
 static const struct k_clock *clockid_to_kclock(const clockid_t id)
 {
-        if (id < 0)
+        clockid_t idx = id;
+
+        if (id < 0) {
                 return (id & CLOCKFD_MASK) == CLOCKFD ?
                         &clock_posix_dynamic : &clock_posix_cpu;
+        }
 
-        if (id >= ARRAY_SIZE(posix_clocks) || !posix_clocks[id])
+        if (id >= ARRAY_SIZE(posix_clocks))
                 return NULL;
-        return posix_clocks[id];
+
+        return posix_clocks[array_index_nospec(idx, ARRAY_SIZE(posix_clocks))];
 }