KEYS: fix writing past end of user-supplied buffer in keyring_read()

[mirror_ubuntu-artful-kernel.git] / security / keys / keyring.c

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index de81793f9920787101dec77eca28ddfbe91ebbc7..94f038967c170eb942d0d7c14cc922e8c8fbe316 100644 (file)
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -423,7 +423,7 @@ static void keyring_describe(const struct key *keyring, struct seq_file *m)
 }
 
 struct keyring_read_iterator_context {
-       size_t                  qty;
+       size_t                  buflen;
        size_t                  count;
        key_serial_t __user     *buffer;
 };
@@ -435,9 +435,9 @@ static int keyring_read_iterator(const void *object, void *data)
        int ret;
 
        kenter("{%s,%d},,{%zu/%zu}",
-              key->type->name, key->serial, ctx->count, ctx->qty);
+              key->type->name, key->serial, ctx->count, ctx->buflen);
 
-       if (ctx->count >= ctx->qty)
+       if (ctx->count >= ctx->buflen)
                return 1;
 
        ret = put_user(key->serial, ctx->buffer);
@@ -472,16 +472,12 @@ static long keyring_read(const struct key *keyring,
                return 0;
 
        /* Calculate how much data we could return */
-       ctx.qty = nr_keys * sizeof(key_serial_t);
-
        if (!buffer || !buflen)
-               return ctx.qty;
-
-       if (buflen > ctx.qty)
-               ctx.qty = buflen;
+               return nr_keys * sizeof(key_serial_t);
 
        /* Copy the IDs of the subscribed keys into the buffer */
        ctx.buffer = (key_serial_t __user *)buffer;
+       ctx.buflen = buflen;
        ctx.count = 0;
        ret = assoc_array_iterate(&keyring->keys, keyring_read_iterator, &ctx);
        if (ret < 0) {