In theory overlayfs could support upper layer directly referring to a data
layer, but there's no current use case for this.
Originally, when data-only layers were introduced, this wasn't allowed,
only introduced by the "datadir+" feture, but without actually handling
this case, resuting in an Oops.
Fix by disallowing datadir without lowerdir.
Reported-by: Giuseppe Scrivano <gscrivan@xxxxxxxxxx>
Fixes: 24e16e385f22 ("ovl: add support for appending lowerdirs one by one")
Cc: <stable@xxxxxxxxxxxxxxx> # v6.7
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
fs/overlayfs/super.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 86ae6f6da36b..b11094acdd8f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1137,6 +1137,11 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
return ERR_PTR(-EINVAL);
}
+ if (ctx->nr == ctx->nr_data) {
+ pr_err("at least one non-data lowerdir is required\n");
+ return ERR_PTR(-EINVAL);
+ }
+
err = -EINVAL;
for (i = 0; i < ctx->nr; i++) {
l = &ctx->lower[i];
--
2.48.1
