kernel: fix minor infoleak in get_user_ex()

[Shawn <citypw () gmail com>]

Hi guys,

I suppose this bug should get a CVE number.

Info:
get_user_ex(x, ptr) should zero x on failure. It's not a lot of a leak
(at most we are leaking uninitialized 64bit value off the kernel
stack, and in a fairly constrained situation, at that), but the fix is
trivial, so... Cc: stable () vger kernel org Signed-off-by: Al Viro
<viro () zeniv linux org uk> [ This sat in different branch from the
uaccess fixes since mid-August ] Signed-off-by: Linus Torvalds
<torvalds () linux-foundation org>

Upstream fix:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1c109fabbd51863475cd12ac206bdd249aee35af

Impact:

According to Spender:

https://lwn.net/Articles/705264/

Mitigation:

PaX/Grsecurity's KERNEXEC/UDEREF
SMEP

-- 
GNU powered it...
GPL protect it...
God blessing it...

regards
Shawn