Instead of using ext4_bread/ext4_getblk.
When I was trying out Linux 5.19-rc3 some symlinks became inaccessible to
me, with the error "Structure needs cleaning" and the following printed in
the kernel message log:
EXT4-fs error (device nvme0n1p1): ext4_map_blocks:599: inode #7351350:
block 774843950: comm readlink: lblock 0 mapped to illegal pblock
774843950 (length 1)
It looks like the ext4_get_link function introduced in commit 6493792d3299
("ext4: convert symlink external data block mapping to bdev") does not
handle links with inline data correctly. I added explicit handling for this
case using ext4_readpage_inline. This fixes the bug and the affected
symlinks become accessible again.
Fixes: 6493792d3299 ("ext4: convert symlink external data block mapping to bdev")
Signed-off-by: Torge Matthies <openglfreak@xxxxxxxxxxxxxx>
---
fs/ext4/symlink.c | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/fs/ext4/symlink.c b/fs/ext4/symlink.c
index d281f5bcc526..ec4fc2d23efc 100644
--- a/fs/ext4/symlink.c
+++ b/fs/ext4/symlink.c
@@ -19,7 +19,10 @@
*/
#include <linux/fs.h>
+#include <linux/gfp.h>
+#include <linux/mm.h>
#include <linux/namei.h>
+#include <linux/pagemap.h>
#include "ext4.h"
#include "xattr.h"
@@ -65,6 +68,37 @@ static int ext4_encrypted_symlink_getattr(struct user_namespace *mnt_userns,
return fscrypt_symlink_getattr(path, stat);
}
+static void ext4_free_link_inline(void *folio)
+{
+ folio_unlock(folio);
+ folio_put(folio);
+}
+
+static const char *ext4_get_link_inline(struct inode *inode,
+ struct delayed_call *callback)
+{
+ struct folio *folio;
+ char *ret;
+ int err;
+
+ folio = folio_alloc(GFP_NOFS, 0);
+ if (!folio)
+ return ERR_PTR(-ENOMEM);
+ folio_lock(folio);
+ folio->index = 0;
+
+ err = ext4_readpage_inline(inode, &folio->page);
+ if (err) {
+ folio_put(folio);
+ return ERR_PTR(err);
+ }
+
+ set_delayed_call(callback, ext4_free_link_inline, folio);
+ ret = folio_address(folio);
+ nd_terminate_link(ret, inode->i_size, inode->i_sb->s_blocksize - 1);
+ return ret;
+}
+
static void ext4_free_link(void *bh)
{
brelse(bh);
@@ -75,6 +109,9 @@ static const char *ext4_get_link(struct dentry *dentry, struct inode *inode,
{
struct buffer_head *bh;
+ if (ext4_has_inline_data(inode))
+ return ext4_get_link_inline(inode, callback);
+
if (!dentry) {
bh = ext4_getblk(NULL, inode, 0, EXT4_GET_BLOCKS_CACHED_NOWAIT);
if (IS_ERR(bh))
--
2.36.1
