cifs: extra sanity checking for cifs.idmap keys
Now that we aren't so rigid about the length of the key being passed
in, we need to be a bit more rigorous about checking the length of
the actual data against the claimed length (a'la num_subauths field).
Check for the case where userspace sends us a seemingly valid key
with a num_subauths field that goes beyond the end of the array. If
that happens, return -EIO and invalidate the key.
Also change the other places where we check for malformed keys in this
code to invalidate the key as well.
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
index 751d34b..b0b114a 100644
--- a/fs/cifs/cifsacl.c
+++ b/fs/cifs/cifsacl.c
@@ -191,6 +191,8 @@
{
int rc;
struct key *sidkey;
+ struct cifs_sid *ksid;
+ unsigned int ksid_size;
char desc[3 + 10 + 1]; /* 3 byte prefix + 10 bytes for value + NULL */
const struct cred *saved_cred;
@@ -211,14 +213,27 @@
rc = -EIO;
cFYI(1, "%s: Downcall contained malformed key "
"(datalen=%hu)", __func__, sidkey->datalen);
- goto out_key_put;
+ goto invalidate_key;
}
- cifs_copy_sid(ssid, (struct cifs_sid *)sidkey->payload.data);
+
+ ksid = (struct cifs_sid *)sidkey->payload.data;
+ ksid_size = CIFS_SID_BASE_SIZE + (ksid->num_subauth * sizeof(__le32));
+ if (ksid_size > sidkey->datalen) {
+ rc = -EIO;
+ cFYI(1, "%s: Downcall contained malformed key (datalen=%hu, "
+ "ksid_size=%u)", __func__, sidkey->datalen, ksid_size);
+ goto invalidate_key;
+ }
+ cifs_copy_sid(ssid, ksid);
out_key_put:
key_put(sidkey);
out_revert_creds:
revert_creds(saved_cred);
return rc;
+
+invalidate_key:
+ key_invalidate(sidkey);
+ goto out_key_put;
}
static int
@@ -264,6 +279,7 @@
rc = -EIO;
cFYI(1, "%s: Downcall contained malformed key "
"(datalen=%hu)", __func__, sidkey->datalen);
+ key_invalidate(sidkey);
goto out_key_put;
}