Commit-ID: 19b558db12f9f4e45a22012bae7b4783e62224da
Gitweb: https://git.kernel.org/tip/19b558db12f9f4e45a22012bae7b4783e62224da
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Thu, 15 Feb 2018 17:21:55 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Thu, 22 Mar 2018 12:29:27 +0100
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@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Rasmus Villemoes <rasmus.villemoes@xxxxxxxxx>
Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: David Woodhouse <dwmw@xxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1802151718320.1296@xxxxxxxxxxxxxxxxxxxxxxx
---
kernel/time/posix-timers.c | 11 ++++++++---
1 file 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))];
}
--
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