Decoding a lower directory file handle to overlay path with cold
inode/dentry cache may go as follows:
1. Decode real lower file handle to lower dir path
2. Check if lower dir is indexed (was copied up)
3. If indexed, get the upper dir path from index
4. Lookup upper dir path in overlay
5. If overlay path found, verify that overlay lower is the lower dir
from step 1
On failure to verify step 5 above, user will get an ESTALE error and
a WARN_ON will be printed.
A mismatch in step 5 could be a result of lower directory that was renamed
while overlay was offline, after that lower directory has been copied
up and indexed.
This is a scripted reproducer based on xfstest overlay/052:
# Create lower subdir
create_dirs
create_test_files $lower/lowertestdir/subdir
mount_dirs
# Copy up lower dir and encode lower subdir file handle
touch $SCRATCH_MNT/lowertestdir
test_file_handles $SCRATCH_MNT/lowertestdir/subdir -p -o $tmp.fhandle
# Rename lower dir offline
unmount_dirs
mv $lower/lowertestdir $lower/lowertestdir.new/
mount_dirs
# Attempt to decode lower subdir file handle
test_file_handles $SCRATCH_MNT -p -i $tmp.fhandle
Since this WARN_ON() can be triggered by user we need to relax it.
Fixes: 4b91c30a5a19 ("ovl: lookup connected ancestor of dir in inode...")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.16+
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/export.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 8f4286450f92..0e696f72cf65 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -476,7 +476,7 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
if (IS_ERR_OR_NULL(this))
return this;
- if (WARN_ON(ovl_dentry_real_at(this, layer->idx) != real)) {
+ if (ovl_dentry_real_at(this, layer->idx) != real) {
dput(this);
this = ERR_PTR(-EIO);
}
--
2.17.1
