posix-timers: Protect posix clock array access against speculation
authorThomas Gleixner <tglx@linutronix.de>
Thu, 15 Feb 2018 16:21:55 +0000 (17:21 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 28 Mar 2018 16:24:46 +0000 (18:24 +0200)
commitf7fbe38cc55bedffcf62874d78c6e455e6a31522
tree0e92458b339f464678c99325659748c38c0ff1b5
parentb08952bbc1712d76c2d63486252073c0406f911f
posix-timers: Protect posix clock array access against speculation

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.linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kernel/time/posix-timers.c