Re: [PATCH 1/2] prctl: more prctl(PR_SET_MM_*) checks

From: Cyrill Gorcunov
Date: Wed May 27 2015 - 18:02:37 EST


On Thu, May 28, 2015 at 12:47:57AM +0300, Alexey Dobriyan wrote:
> Individual prctl(PR_SET_MM_*) calls do some checking to maintain
> consistent view of mm->arg_start et al fields, but not enough.
> In particular PR_SET_MM_ARG_START/PR_SET_MM_ARG_END/PR_SET_MM_ENV_START/PR_SET_MM_ENV_END
> only check that address lies in existent VMA, but doesn't check that
> start address is lower that end address _at all_.
>
> Consolidate all consistency checks, so there will be no difference in
> the future between PR_SET_MM_MAP and individual PR_SET_MM_* calls.
>
> The program below makes both ARGV and ENVP areas reverted,
> makes /proc/$PID/cmdline show garbage (doesn't oops by luck).

Why should it oops? Actually i would really love to drop off old
PR_SET_MM_ interface completely (which requires CAP_SYS_RESOURCE),
leaving only MM_MAP. But thank you!

Acked-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
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