On Sat, Nov 16, 2013 at 11:01 AM, Oleg Nesterov <oleg@xxxxxxxxxx> 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@xxxxxxxxxx> I can't speak to the bitops/cmpxchg, but the rest looks fine to me. Acked-by: Kees Cook <keescook@xxxxxxxxxxxx> Thanks! -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
