[PATCH review 0/7] Bind mount escape fixes

Al Viro viro at ZenIV.linux.org.uk
Fri Aug 21 07:51:05 UTC 2015


On Sun, Aug 16, 2015 at 06:33:21AM -0500, Eric W. Biederman wrote:

> > ... or either of us can do merging those checks into a single place,
> > be it as a followup to your 7-patch series, or folded with the
> > fs/dcache.c-affecting patches in there.  If you have no time left, I can
> > certainly do that followup myself - not a problem[1]
> 
> I don't have time.  Everytime I have worked with this it has take pretty
> much full days of staring at the code, and I don't have any more full
> days left before the merge window.

OK, at that point I've pretty much given up on fs_pin for this cycle.
And testing your variant with unconditional checks on .. appears to have
fairly low overhead.  I still want to deal with catching and unmounting the
unreachable suckers, so fs/dcache.c side of things will get used when we get
to that stuff, but for now I've taken your 1/7, 2/7 plus the variant of
"vfs: Test for and handle paths that are unreachable from their mnt_root"
that doesn't care whether anything escaped or not.

3--6 are held in a local branch for now; I *am* going to use them
come next cycle.  And there's another pile of fun around that area, also
for the next cycle - kernel-initiated subtree removals on things like
sysfs et.al.; handling of the locking in those is inconsistent and tied
with the fun we have for d_move()/__d_unalias().  Sigh...


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