Re: [tip:x86/mm] x86/mmap, ASLR: Do not treat unlimited-stack tasks as legacy mmap
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- Subject: Re: [tip:x86/mm] x86/mmap, ASLR: Do not treat unlimited-stack tasks as legacy mmap
- From: Jiri Kosina <jikos@xxxxxxxxxx>
- Date: Tue, 27 Jun 2017 10:00:23 +0200 (CEST)
- Cc: tip-bot for Michal Hocko <tipbot@xxxxxxxxx>, linux-tip-commits@xxxxxxxxxxxxxxx, torvalds@xxxxxxxxxxxxxxxxxxxx, mingo@xxxxxxxxxx, hpa@xxxxxxxxx, mhocko@xxxxxxxx, tglx@xxxxxxxxxxxxx, davej@xxxxxxxxxxxxxxxxx, peterz@xxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
- In-reply-to: <20170623145441.GB9388@redhat.com>
- References: <20170614082218.12450-1-mhocko@kernel.org> <tip-86b110d2ae6365ce91cabd37588bc8611770421a@git.kernel.org> <20170623145441.GB9388@redhat.com>
- User-agent: Alpine 2.20 (LSU 67 2015-01-07)
On Fri, 23 Jun 2017, Oleg Nesterov wrote:
> > We added a heuristics to treat applications with RLIMIT_STACK configured
> > to unlimited as legacy. This means:
>
> To me this also means a minor security problem. The comment above
> PER_CLEAR_ON_SETID says "must be cleared upon setuid or setgid exec",
> but if you do "ulimit -s unlimited" before suid exec then
> ADDR_COMPAT_LAYOUT set by security checks will be ignored.
Could you please be a bit more specific here?
mmap_is_legacy() *first* checks for the ADDR_COMPAT_LAYOUT in the
personality flags, and only then, if it's unset, RLIMIT_STACK comes to
play.
Thanks,
--
Jiri Kosina
SUSE Labs
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