[PATCH 3.16 236/328] cifs: prevent integer overflow in nxt_dir_entry()

Ben Hutchings
2018-12-09T22:22:09Z

From: Dan Carpenter <dan.carpenter@oracle.com>

commit 8ad8aa353524d89fa2e09522f3078166ff78ec42 upstream.

The "old_entry + le32_to_cpu(pDirInfo->NextEntryOffset)" can wrap
around so I have added a check for integer overflow.

Reported-by: Dr Silvio Cesare of InfoSect <silvio.cesare@gmail.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/cifs/readdir.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -370,8 +370,15 @@ static char *nxt_dir_entry(char *old_ent

new_entry = old_entry + sizeof(FIND_FILE_STANDARD_INFO) +
pfData->FileNameLength;
- } else
- new_entry = old_entry + le32_to_cpu(pDirInfo->NextEntryOffset);
+ } else {
+ u32 next_offset = le32_to_cpu(pDirInfo->NextEntryOffset);
+
+ if (old_entry + next_offset < old_entry) {
+ cifs_dbg(VFS, "invalid offset %u\n", next_offset);
+ return NULL;
+ }
+ new_entry = old_entry + next_offset;
+ }
cifs_dbg(FYI, "new entry %p old entry %p\n", new_entry, old_entry);
/* validate that new_entry is not past end of SMB */
if (new_entry >= end_of_smb) {