| From | Ben Hutchings <> | Date | Wed, 30 May 2018 11:52:42 +0100 | Subject | [PATCH 3.2 140/153] posix-timers: Protect posix clock array access against speculation |
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3.2.102-rc1 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: 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 [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 <ben@decadent.org.uk> --- --- 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)
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