linux-kernel - [PATCH v2 0/3] sysctl: fix range-checking in do_proc_dointvec_minmax

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Date:   Thu,  7 Feb 2019 06:34:23 -0600
From:   Zev Weiss <zev@...ilderbeest.net>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>, yzaikin@...gle.com,
        brendanhiggins@...gle.com
Subject: [PATCH v2 0/3] sysctl: fix range-checking in do_proc_dointvec_minmax_conv()

Hello,

After being left with an unusable system after a typo executing
something like 'echo $((1<<24)) > /proc/sys/vm/max_map_count', I found
that do_proc_dointvec_minmax_conv() was missing a check to ensure that
the converted value actually fits in an int.

The first of the following patches enhances the sysctl selftest such
that it detects this problem; the second provides a minimal fix
(suitable for -stable) such that the selftest passes.  The third patch
then performs a more thorough refactoring to eliminate the code
duplication that led to the bug in the first place (maintaining the
passing status of the selftest).

Changes in v2:
 - Rearranged selftest to also test negative values and provide more
   info in comments
 - Added intermediate patch as a minimal fix for -stable without the
   refactoring

Thanks,
Zev Weiss