On Tue, Jul 1, 2014 at 2:21 AM, Mateusz Guzik <m...@freebsd.org> wrote: > Author: mjg > Date: Tue Jul 1 09:21:32 2014 > New Revision: 268087 > URL: http://svnweb.freebsd.org/changeset/base/268087 > > Log: > Don't call crcopysafe or uifind unnecessarily in execve.
I'm not sure the code works. It gets a copy of the pointer p_ucred under the PROC_LOCK. The PROC_LOCK is released before newcred = crdup(oldcred) is called. Thus you may be copying an old version of the credentials if any of the other functions that modify them run in the meantime. Maybe this can't happen because the process is single-threaded at the time and all the other sets of p_ucred come via a syscall. I didn't look at all the functions in the kernel which set p_ucred. But only in the case that none of them can run during do_execve this code would be safe. In which case it at least deserves a comment indicating the code is violating the normal locking and safety on p_ucred. There's no assert in the do_execve() code, but kern_execve() will force single-threaded before calling do_execve(). Also, what is the motivation to avoid the crcopy? Is there a measurable performance impact? Thanks, matthew _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
