lib/digsig: additional sanity checks against badly formated key payload

Added sanity checks for possible wrongly formatted key payload data:
- minimum key payload size
- zero modulus length
- corrected upper key payload boundary.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>
Reviewed-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/lib/digsig.c b/lib/digsig.c
index fd2402f67f89..5d840ac64fb1 100644
--- a/lib/digsig.c
+++ b/lib/digsig.c
@@ -105,6 +105,10 @@ static int digsig_verify_rsa(struct key *key,
 
         down_read(&key->sem);
         ukp = key->payload.data;
+
+        if (ukp->datalen < sizeof(*pkh))
+                goto err1;
+
         pkh = (struct pubkey_hdr *)ukp->data;
 
         if (pkh->version != 1)
@@ -117,7 +121,7 @@ static int digsig_verify_rsa(struct key *key,
                 goto err1;
 
         datap = pkh->mpi;
-        endp = datap + ukp->datalen;
+        endp = ukp->data + ukp->datalen;
 
         for (i = 0; i < pkh->nmpi; i++) {
                 unsigned int remaining = endp - datap;
@@ -128,7 +132,8 @@ static int digsig_verify_rsa(struct key *key,
         mblen = mpi_get_nbits(pkey[0]);
         mlen = (mblen + 7)/8;
 
-        err = -ENOMEM;
+        if (mlen == 0)
+                goto err;
 
         out1 = kzalloc(mlen, GFP_KERNEL);
         if (!out1)