3.2.102-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Thomas Gleixner <[email protected]> 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 <[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: Linus Torvalds <[email protected]> Cc: David Woodhouse <[email protected]> Link: https://lkml.kernel.org/r/[email protected] [bwh: Backported to 3.2: - Move the test of the clock_getres field below the lookup using array_index_nospec() - Adjust filename, context] Signed-off-by: Ben Hutchings <[email protected]> --- --- a/kernel/posix-timers.c +++ b/kernel/posix-timers.c @@ -47,6 +47,7 @@ #include <linux/wait.h> #include <linux/workqueue.h> #include <linux/export.h> +#include <linux/nospec.h> /* * Management arrays for POSIX timers. Timers are kept in slab memory @@ -520,13 +521,21 @@ static void release_posix_timer(struct k static struct k_clock *clockid_to_kclock(const clockid_t id) { - if (id < 0) + clockid_t idx = id; + struct k_clock *kc; + + if (id < 0) { return (id & CLOCKFD_MASK) == CLOCKFD ? &clock_posix_dynamic : &clock_posix_cpu; + } + + if (id >= ARRAY_SIZE(posix_clocks)) + return NULL; - if (id >= MAX_CLOCKS || !posix_clocks[id].clock_getres) + kc = &posix_clocks[array_index_nospec(idx, ARRAY_SIZE(posix_clocks))]; + if (!kc->clock_getres) return NULL; - return &posix_clocks[id]; + return kc; } static int common_timer_create(struct k_itimer *new_timer)
