Messages in this thread |  | | Date | Mon, 18 Nov 2013 08:36:48 -0800 | Subject | Re: [PATCH 1/3] set_dumpable: fix the theoretical race with itself | From | Kees Cook <> |
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On Sat, Nov 16, 2013 at 11:01 AM, Oleg Nesterov <oleg@redhat.com> wrote: > set_dumpable() updates MMF_DUMPABLE_MASK in a non-trivial way to > ensure that get_dumpable() can't observe the intermediate state, > but this all can't help if multiple threads call set_dumpable() > at the same time. > > And in theory commit_creds()->set_dumpable(SUID_DUMP_ROOT) racing > with sys_prctl()->set_dumpable(SUID_DUMP_DISABLE) can result in > SUID_DUMP_USER. > > Change this code to update both bits atomically via cmpxchg(). > > Note: this assumes that it is safe to mix bitops and cmpxchg. IOW, > if, say, an architecture implements cmpxchg() using the locking > (like arch/parisc/lib/bitops.c does), then it should use the same > locks for set_bit/etc. > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
I can't speak to the bitops/cmpxchg, but the rest looks fine to me.
Acked-by: Kees Cook <keescook@chromium.org>
Thanks!
-Kees
-- Kees Cook Chrome OS Security
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