[SECURITY PATCH 27/30] fs/f2fs: Do not copy file names that are too long

[Daniel Kiper]

From: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>

A corrupt f2fs file system might specify a name length which is greater
than the maximum name length supported by the GRUB f2fs driver.

We will allocate enough memory to store the overly long name, but there
are only F2FS_NAME_LEN bytes in the source, so we would read past the end
of the source.

While checking directory entries, do not copy a file name with an invalid
length.

Signed-off-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/f2fs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/grub-core/fs/f2fs.c b/grub-core/fs/f2fs.c
index 8898b235e..df6beb544 100644
--- a/grub-core/fs/f2fs.c
+++ b/grub-core/fs/f2fs.c
@@ -1003,6 +1003,10 @@ grub_f2fs_check_dentries (struct grub_f2fs_dir_iter_ctx 
*ctx)
 
       ftype = ctx->dentry[i].file_type;
       name_len = grub_le_to_cpu16 (ctx->dentry[i].name_len);
+
+      if (name_len >= F2FS_NAME_LEN)
+        return 0;
+
       filename = grub_malloc (name_len + 1);
       if (!filename)
         return 0;
-- 
2.11.0