libselinux: simplify procattr cache
https://github.com/systemd/systemd/issues/475 identified a problem
in libselinux with using getpid(3) rather than getpid(2) due to direct
use of the clone() system call by systemd. We could change libselinux
to use getpid(2) instead, but this would impose a getpid(2) system call
overhead on each get*con() or set*con() call. Rather than do this,
we can instead simplify the procattr cache and get rid of the
caching of the pid and tid entirely, along with the atfork handler.
With commit 3430519109c0423a49b9350aa8444beec798d5a7 ("use
/proc/thread-self when available"), we only need the tid when
on Linux < 3.17, so we can just always call gettid() in that case (as
done prior to the procattr cache) and drop the cached tid. The cached
pid and atfork handlers were only needed to reset the cached tid, so
those can also be dropped. The rest of the cached attributes are not
reset by the kernel on fork, only on exec, so we do not need to
flush them upon fork/clone.
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
1 file changed