From: Eric Wong <e@80x24.org>
Date: Wed, 07 Sep 2016 18:10:36 GMT
Subject: Re: [PATCH v1 2/2] read-cache: make sure file handles are not inherited by child processes
Message-ID: <20160907181036.GA14931@starla>
In-Reply-To: <7B903664-0324-4375-A81C-1317020CBE9B@gmail.com>

Lars Schneider <larsxschneider@gmail.com> wrote:
> > On 06 Sep 2016, at 23:06, Eric Wong <e@80x24.org> wrote:
> > larsxschneider@gmail.com wrote:
> >> static int ce_compare_data(const struct cache_entry *ce, struct stat *st)
> >> {
> >> 	int match = -1;
> >> -	int fd = open(ce->name, O_RDONLY);
> >> +	int fd = open(ce->name, O_RDONLY | O_CLOEXEC);
> >> 
> >> 	if (fd >= 0) {
> >> 		unsigned char sha1[20];
> > 
> > Also, this needs to check EINVAL when O_CLOEXEC != 0 the same
> > way create_tempfile currently does.  Somebody could be building
> > with modern headers but running an old kernel that doesn't
> > understand O_CLOEXEC.
> > 
> > There should probably be a open() wrapper for handling this case
> > since we're now up to 3 places where open(... O_CLOEXEC) is
> > used.
> 
> Right! Actually "sha1_file.c:git_open_noatime()" is already a wrapper, no?
> Can't we use this here? The O_NOATIME flag shouldn't hurt, right?

For ce_compare_data (and other O_RDONLY users), I guess
git_open_noatime is fine; and probably preferable because of
O_NOATIME.

We probably should be using O_NOATIME for all O_RDONLY cases
to get the last bit of performance out (especially since
non-modern-Linux systems probably still lack relatime).

However, create_tempfile needs O_RDWR|O_CREAT|O_EXCL
but I guess we can clean that up in another series.