Messages in this thread | | | From | Andrei Vagin <> | Date | Tue, 20 Jul 2021 00:33:11 -0700 | Subject | Re: [PATCH] prctl: allow to setup brk for et_dyn executables |
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On Thu, Jan 21, 2021 at 2:12 PM Cyrill Gorcunov <gorcunov@gmail.com> wrote: > > Keno Fischer reported that when a binray loaded via > ld-linux-x the prctl(PR_SET_MM_MAP) doesn't allow to > setup brk value because it lays before mm:end_data. > > For example a test program shows > > | # ~/t > | > | start_code 401000 > | end_code 401a15 > | start_stack 7ffce4577dd0 > | start_data 403e10 > | end_data 40408c > | start_brk b5b000 > | sbrk(0) b5b000 > > and when executed via ld-linux > > | # /lib64/ld-linux-x86-64.so.2 ~/t > | > | start_code 7fc25b0a4000 > | end_code 7fc25b0c4524 > | start_stack 7fffcc6b2400 > | start_data 7fc25b0ce4c0 > | end_data 7fc25b0cff98 > | start_brk 55555710c000 > | sbrk(0) 55555710c000 > > This of course prevent criu from restoring such programs. > Looking into how kernel operates with brk/start_brk inside > brk() syscall I don't see any problem if we allow to setup > brk/start_brk without checking for end_data. Even if someone > pass some weird address here on a purpose then the worst > possible result will be an unexpected unmapping of existing > vma (own vma, since prctl works with the callers memory) but > test for RLIMIT_DATA is still valid and a user won't be able > to gain more memory in case of expanding VMAs via new values > shipped with prctl call. > > Reported-by: Keno Fischer <keno@juliacomputing.com> > Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com> > CC: Andrew Morton <akpm@linux-foundation.org> > CC: Dmitry Safonov <0x7f454c46@gmail.com> > CC: Andrey Vagin <avagin@gmail.com>
Acked-by: Andrey Vagin <avagin@gmail.com> Fixes: bbdc6076d2e5 ("binfmt_elf: move brk out of mmap when doing direct loader exec")
> CC: Kirill Tkhai <ktkhai@virtuozzo.com> > CC: Eric W. Biederman <ebiederm@xmission.com> > --- > Guys, take a look please once time permit. Hopefully I didn't > miss something 'cause made this patch via code reading only. > > Andrey, do we still have a criu container which tests new kernels, > right? Would be great to run criu tests with this patch applied > to make sure everything is intact.
Sorry for the delay. I run tests and everything works as expected.
Thanks, Andrei
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