linux-kernel - Re: [PATCH 1/2] alpha: osf_sys.c: fix put

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Date:   Tue, 7 Nov 2017 15:52:22 +0000
From:   Al Viro <viro@...IV.linux.org.uk>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>, y2038@...ts.linaro.org,
        Deepa Dinamani <deepa.kernel@...il.com>,
        stable@...r.kernel.org, linux-alpha@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] alpha: osf_sys.c: fix put_tv32 regression

On Tue, Nov 07, 2017 at 03:09:24PM +0100, Arnd Bergmann wrote:
> There was a typo in the new version of put_tv32() that caused
> uninitialized stack data to be written back to user space, rather
> than writing the actual timeval for the emulation of
> gettimeofday(), wait4(), usleep_thread() and old_adjtimex().
> 
> This fixes it to write the correct data again.

*blink*

the bug is real, all right, and the fix is correct one, but where
do you get an infoleak?  What it is is a user-triggerable oops -
just pass it an unmapped address.  For anything mapped r/w it's
simply a no-op - userland data is unchanged.

IOW, the fix is correct, but commit message isn't - it's

"user-triggerable oops and in all cases failed to modify userland timeval32"

not

"uninitialized stack data to be written back to user space"