posix-timers: Protect posix clock array access against speculation
commit 19b558db12
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.linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/10/head
parent
b08952bbc1
commit
f7fbe38cc5
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@ -50,6 +50,7 @@
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#include <linux/export.h>
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#include <linux/hashtable.h>
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#include <linux/compat.h>
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#include <linux/nospec.h>
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#include "timekeeping.h"
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#include "posix-timers.h"
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@ -1346,11 +1347,15 @@ static const struct k_clock * const posix_clocks[] = {
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static const struct k_clock *clockid_to_kclock(const clockid_t id)
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{
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if (id < 0)
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clockid_t idx = id;
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if (id < 0) {
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return (id & CLOCKFD_MASK) == CLOCKFD ?
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&clock_posix_dynamic : &clock_posix_cpu;
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}
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if (id >= ARRAY_SIZE(posix_clocks) || !posix_clocks[id])
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if (id >= ARRAY_SIZE(posix_clocks))
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return NULL;
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return posix_clocks[id];
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return posix_clocks[array_index_nospec(idx, ARRAY_SIZE(posix_clocks))];
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}
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