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| author | Cyrill Gorcunov <gorcunov@gmail.com> | 2021-09-07 20:00:41 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-09-08 11:50:28 -0700 |
| commit | e1fbbd073137a9d63279f6bf363151a938347640 (patch) | |
| tree | 88d61d4cb3a19f4fefb2b14fa87bac00fe8a71c2 /kernel | |
| parent | 5b91a75b3312c03798f555e10569fd85211a490c (diff) | |
| download | lwn-e1fbbd073137a9d63279f6bf363151a938347640.tar.gz lwn-e1fbbd073137a9d63279f6bf363151a938347640.zip | |
prctl: allow to setup brk for et_dyn executables
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.
Link: https://lkml.kernel.org/r/20210121221207.GB2174@grain
Fixes: bbdc6076d2e5 ("binfmt_elf: move brk out of mmap when doing direct loader exec")
Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reported-by: Keno Fischer <keno@juliacomputing.com>
Acked-by: Andrey Vagin <avagin@gmail.com>
Tested-by: Andrey Vagin <avagin@gmail.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Cc: Alexander Mikhalitsyn <alexander.mikhalitsyn@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sys.c | 7 |
1 files changed, 0 insertions, 7 deletions
diff --git a/kernel/sys.c b/kernel/sys.c index ef1a78f5d71c..6ec50924b517 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -1960,13 +1960,6 @@ static int validate_prctl_map_addr(struct prctl_mm_map *prctl_map) error = -EINVAL; /* - * @brk should be after @end_data in traditional maps. - */ - if (prctl_map->start_brk <= prctl_map->end_data || - prctl_map->brk <= prctl_map->end_data) - goto out; - - /* * Neither we should allow to override limits if they set. */ if (check_data_rlimit(rlimit(RLIMIT_DATA), prctl_map->brk, |