4.15-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner tglx@linutronix.de
commit 19b558db12f9f4e45a22012bae7b4783e62224da upstream.
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.linut... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/time/posix-timers.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
--- 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 posi
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))]; }