On Tue, Jun 02, 2020 at 11:23:38AM -0400, Vivek Goyal wrote: > Amir pointed me to metacopy test cases in unionmount-testsuite and > I decided to run "./run --ov=10 --meta" and it failed while running > test "rename-mass-5.py". Hi Miklos, This patch applies on top of the patch series I posted previously. https://marc.info/?l=linux-unionfs&m=159102703820108&w=2 Thanks Vivek > > Problem is w.r.t absolute redirect traversal on intermediate metacopy > dentry. We do not store intermediate metacopy dentries and also skip > current loop/layer and move onto lookup in next layer. But at the end > of loop, we have logic to reset "poe" and layer index if currnently > looked up dentry has absolute redirect. We skip all that and that > means lookup in next layer will fail. > > Following is simple test case to reproduce this. > > - mkdir -p lower upper work merged lower/a lower/b > - touch lower/a/foo.txt > - mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work,metacopy=on none merged > > # Following will create absolute redirect "/a/foo.txt" on upper/b/bar.txt. > - mv merged/a/foo.txt merged/b/bar.txt > > # unmount overlay and use upper as lower layer (lower2) for next mount. > - umount merged > - mv upper lower2 > - rm -rf work; mkdir -p upper work > - mount -t overlay -o lowerdir=lower2:lower,upperdir=upper,workdir=work,metacopy=on none merged > > # Force a metacopy copy-up > - chown bin:bin merged/b/bar.txt > > # unmount overlay and use upper as lower layer (lower3) for next mount. > - umount merged > - mv upper lower3 > - rm -rf work; mkdir -p upper work > - mount -t overlay -o lowerdir=lower3:lower2:lower,upperdir=upper,workdir=work,metacopy=on none merged > > # ls merged/b/bar.txt > ls: cannot access 'bar.txt': Input/output error > > Intermediate lower layer (lower2) has metacopy dentry b/bar.txt with absolute > redirect "/a/foo.txt". We skipped redirect processing at the end of loop > which sets poe to roe and sets the appropriate next lower layer index. And > that means lookup failed in next layer. > > Fix this by continuing the loop for any intermediate dentries. We still do not > save these at lower stack. With this fix applied unionmount-testsuite, > "./run --ov-10 --meta" now passes. > > Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx> > --- > fs/overlayfs/namei.c | 26 ++++++++++++++------------ > 1 file changed, 14 insertions(+), 12 deletions(-) > > diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c > index da05e33db9ce..df81ec0e179f 100644 > --- a/fs/overlayfs/namei.c > +++ b/fs/overlayfs/namei.c > @@ -913,15 +913,6 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, > goto out_put; > } > > - /* > - * Do not store intermediate metacopy dentries in chain, > - * except top most lower metacopy dentry > - */ > - if (d.metacopy && ctr) { > - dput(this); > - continue; > - } > - > /* > * If no origin fh is stored in upper of a merge dir, store fh > * of lower dir and set upper parent "impure". > @@ -956,9 +947,20 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, > origin = this; > } > > - stack[ctr].dentry = this; > - stack[ctr].layer = lower.layer; > - ctr++; > + if (d.metacopy && ctr) { > + /* > + * Do not store intermediate metacopy dentries in > + * lower chain, except top most lower metacopy dentry. > + * Continue the loop so that if there is an absolute > + * redirect on this dentry, poe can be reset to roe. > + */ > + dput(this); > + this = NULL; > + } else { > + stack[ctr].dentry = this; > + stack[ctr].layer = lower.layer; > + ctr++; > + } > > /* > * Following redirects can have security consequences: it's like > -- > 2.25.4 >
