[PATCH v2 2/4] fs: cramfs: return an error pointer from cramfs_get_link()

[Sascha Hauer <s.hauer@pengutronix.de>]

cramfs_get_link() checks the result of cramfs_read_file() for a negative
value, which it never returns: when a block fails to decompress, it
stops and returns how much it has copied so far. A link that can't be
read is therefore returned as if it could, with its unread part zeroed,
and stays cached in inode->i_link.

Treat a short read as -EIO, drop the buffer and return an error pointer.
Not NULL, which the check would have returned: readlinkat() checks the
link only with IS_ERR() before copying from it, and path lookup takes
NULL to mean that the link has already been followed.

Fixes: 0a5e0f40f9 ("fs: cramfs: Switch to dentry cache implementation")
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 fs/cramfs/cramfs.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/cramfs/cramfs.c b/fs/cramfs/cramfs.c
index fcb9aeeab8..b41c852758 100644
--- a/fs/cramfs/cramfs.c
+++ b/fs/cramfs/cramfs.c
@@ -432,8 +432,11 @@ static const char *cramfs_get_link(struct dentry *dentry, struct inode *inode)
 	inode->i_link = xzalloc(size_add(inode->i_size, 1));
 
 	ret = cramfs_read_file(inode, 0, inode->i_link, inode->i_size);
-	if (ret < 0)
-		return NULL;
+	if (ret != inode->i_size) {
+		free(inode->i_link);
+		inode->i_link = NULL;
+		return ERR_PTR(-EIO);
+	}
 
 	return inode->i_link;
 }

-- 
2.47.3