xfs_repair: properly detect reserved attribute names

This function in xfs_repair tries to make sure that if an attr name reserved for acls exists in the root namespace, then its value is a valid acl.

However, because it only compares up to the length of the reserved name, superstrings may match and cause false positive xfs_repair errors.

Ensure that both the length and the content match before flagging it as an error.

Spotted-by Zach Brown <[email protected]>

Signed-off-by Eric Sandeen <[email protected]>

---

repair/attr_repair.c +4 -3

index 27442c4..89a5bbf 100644
@@ -747,9 +747,10 @@ valuecheck(
 	void *valuep;
 	int clearit = 0;
 
-	if ((strncmp(namevalue, SGI_ACL_FILE, SGI_ACL_FILE_SIZE) == 0) ||
-			(strncmp(namevalue, SGI_ACL_DEFAULT,
-				SGI_ACL_DEFAULT_SIZE) == 0)) {
+	if ((namelen == SGI_ACL_FILE_SIZE &&
+	     strncmp(namevalue, SGI_ACL_FILE, SGI_ACL_FILE_SIZE) == 0) ||
+	    (namelen == SGI_ACL_DEFAULT_SIZE &&
+	     strncmp(namevalue, SGI_ACL_DEFAULT, SGI_ACL_DEFAULT_SIZE) == 0)) {
 		if (value == NULL) {
 			valuep = malloc(valuelen);
 			if (!valuep)

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Quoted 8 lines · Eric Sandeen

This function in xfs_repair tries to make sure that if an attr name reserved for acls exists in the root namespace, then its value is a valid acl.

However, because it only compares up to the length of the reserved name, superstrings may match and cause false positive xfs_repair errors.

Quoted 6 lines

Ensure that both the length and the content match before flagging it as an error.

Spotted-by Zach Brown <[email protected]>

Signed-off-by Eric Sandeen <[email protected]>

---

Looks good:

Reviewed-by Brian Foster <[email protected]>

So it looks like master doesn't have the sizeof(unsigned char *) problem and the 4.1 update branch does, so we want to make sure that kernel fix makes it into the latter...