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Commit 86eaa130 authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
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ovl: unbless lower st_ino of unverified origin 



On a malformed overlay, several redirected dirs can point to the same
dir on a lower layer. This presents a similar challenge as broken
hardlinks, because different objects in the overlay can return the same
st_ino/st_dev pair from stat(2).

For broken hardlinks, we do not provide constant st_ino on copy up to
avoid this inconsistency. When NFS export feature is enabled, apply
the same logic to files and directories with unverified lower origin.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 37b12916

fs/overlayfs/inode.c

+12 −4
Original line number Diff line number Diff line
@@ -105,12 +105,20 @@ int ovl_getattr(const struct path *path, struct kstat *stat, 
			 * Lower hardlinks may be broken on copy up to different

			 * upper files, so we cannot use the lower origin st_ino

			 * for those different files, even for the same fs case.

			 *

			 * Similarly, several redirected dirs can point to the

			 * same dir on a lower layer. With the "verify_lower"

			 * feature, we do not use the lower origin st_ino, if

			 * we haven't verified that this redirect is unique.

			 *

			 * With inodes index enabled, it is safe to use st_ino

			 * of an indexed hardlinked origin. The index validates

			 * that the upper hardlink is not broken.

			 * of an indexed origin. The index validates that the

			 * upper hardlink is not broken and that a redirected

			 * dir is the only redirect to that origin.

			 */

			if (is_dir || lowerstat.nlink == 1 ||

			    ovl_test_flag(OVL_INDEX, d_inode(dentry)))

			if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) ||

			    (!ovl_verify_lower(dentry->d_sb) &&

			     (is_dir || lowerstat.nlink == 1)))

				stat->ino = lowerstat.ino;



			if (samefs)