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authorThomas Gleixner <tglx@linutronix.de>2018-02-15 19:21:55 +0300
committerThomas Gleixner <tglx@linutronix.de>2018-03-22 14:29:27 +0300
commit19b558db12f9f4e45a22012bae7b4783e62224da (patch)
treed91df798e8cd88baaa332066c7a9892d81f7309c
parent1b5f3ba415fe4cf8b8b39c8d104ed44cde330658 (diff)
downloadlinux-19b558db12f9f4e45a22012bae7b4783e62224da.tar.xz
posix-timers: Protect posix clock array access against speculation
The clockid argument of clockid_to_kclock() comes straight from user space via various syscalls and is used as index into the posix_clocks array. Protect it against spectre v1 array out of bounds speculation. Remove the redundant check for !posix_clock[id] as this is another source for speculation and does not provide any advantage over the return posix_clock[id] path which returns NULL in that case anyway. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Dan Williams <dan.j.williams@intel.com> Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk> Cc: Greg KH <gregkh@linuxfoundation.org> Cc: stable@vger.kernel.org Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: David Woodhouse <dwmw@amazon.co.uk> Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1802151718320.1296@nanos.tec.linutronix.de
-rw-r--r--kernel/time/posix-timers.c11
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))];
}