Commit 1b81dddd authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
Browse files

ovl: fix corner case of conflicting lower layer uuid 



This fixes ovl_lower_uuid_ok() to correctly detect the corner case:
 - two filesystems, A and B, both have null uuid
 - upper layer is on A
 - lower layer 1 is also on A
 - lower layer 2 is on B

In this case, bad_uuid would not have been set for B, because the check
only involved the list of lower fs.  Hence we'll try to decode a layer 2
origin on layer 1 and fail.

We check for conflicting (and null) uuid among all lower layers, including
those layers that are on the same fs as the upper layer.

Reported-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 07f1e596

fs/overlayfs/ovl_entry.h

+2 −0
Original line number Diff line number Diff line
@@ -24,6 +24,8 @@ struct ovl_sb { 
	dev_t pseudo_dev;

	/* Unusable (conflicting) uuid */

	bool bad_uuid;

	/* Used as a lower layer (but maybe also as upper) */

	bool is_lower;

};



struct ovl_layer {

fs/overlayfs/super.c

+6 −2
Original line number Diff line number Diff line
@@ -1260,7 +1260,7 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) 
	if (!ofs->config.nfs_export && !ofs->upper_mnt)

		return true;



	for (i = 1; i < ofs->numfs; i++) {

	for (i = 0; i < ofs->numfs; i++) {

		/*

		 * We use uuid to associate an overlay lower file handle with a

		 * lower layer, so we can accept lower fs with null uuid as long
@@ -1268,7 +1268,8 @@ static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid) 
		 * if we detect multiple lower fs with the same uuid, we

		 * disable lower file handle decoding on all of them.

		 */

		if (uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {

		if (ofs->fs[i].is_lower &&

		    uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {

			ofs->fs[i].bad_uuid = true;

			return false;

		}
@@ -1342,10 +1343,12 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, 
	/*

	 * All lower layers that share the same fs as upper layer, use the real

	 * upper st_dev.

	 * is_lower will be set if upper fs is shared with a lower layer.

	 */

	if (ofs->upper_mnt) {

		ofs->fs[0].sb = ofs->upper_mnt->mnt_sb;

		ofs->fs[0].pseudo_dev = ofs->upper_mnt->mnt_sb->s_dev;

		ofs->fs[0].is_lower = false;

	}



	for (i = 0; i < numlower; i++) {
@@ -1387,6 +1390,7 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, 
		ofs->layers[ofs->numlayer].fsid = fsid;

		ofs->layers[ofs->numlayer].fs = &ofs->fs[fsid];

		ofs->numlayer++;

		ofs->fs[fsid].is_lower = true;

	}



	/*

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