Commit-ID: 19b558db12f9f4e45a22012bae7b4783e62224da Gitweb: https://git.kernel.org/tip/19b558db12f9f4e45a22012bae7b4783e62224da Author: Thomas Gleixner <[email protected]> AuthorDate: Thu, 15 Feb 2018 17:21:55 +0100 Committer: Thomas Gleixner <[email protected]> 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 <[email protected]> Acked-by: Peter Zijlstra (Intel) <[email protected]> Acked-by: Dan Williams <[email protected]> Cc: Rasmus Villemoes <[email protected]> Cc: Greg KH <[email protected]> Cc: [email protected] Cc: Linus Torvalds <[email protected]> Cc: David Woodhouse <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- 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))]; }
