eCryptfs: fix Tag 11 writing code

Fix up the Tag 11 writing code to handle size limits and boundaries more
explicitly.  It looks like the packet length was 1 shorter than it should have
been, chopping off the last byte of the key identifier.  This is largely
inconsequential, since it is not much more likely that a key identifier
collision will occur with 7 bytes rather than 8.  This patch fixes the packet
to use the full number of bytes that were originally intended to be used for
the key identifier.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index aedff50..190e2a0 100644 (file)
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -1449,47 +1449,52 @@ out:
  * Returns zero on success; non-zero on error.
  */
 static int
-write_tag_11_packet(char *dest, int max, char *contents, size_t contents_length,
-                   size_t *packet_length)
+write_tag_11_packet(char *dest, int *remaining_bytes, char *contents,
+                   size_t contents_length, size_t *packet_length)
 {
        size_t packet_size_length;
+       size_t max_packet_size;
        int rc = 0;
 
        (*packet_length) = 0;
-       if ((13 + contents_length) > max) {
+       /* This format is inspired by OpenPGP; see RFC 2440
+        * packet tag 11 */
+       max_packet_size = (1                   /* Tag 11 identifier */
+                          + 3                 /* Max Tag 11 packet size */
+                          + 1                 /* Binary format specifier */
+                          + 1                 /* Filename length */
+                          + 8                 /* Filename ("_CONSOLE") */
+                          + 4                 /* Modification date */
+                          + contents_length); /* Literal data */
+       if (max_packet_size > (*remaining_bytes)) {
+               printk(KERN_ERR "Packet length larger than maximum allowable; "
+                      "need up to [%d] bytes, but there are only [%d] "
+                      "available\n", max_packet_size, (*remaining_bytes));
                rc = -EINVAL;
-               ecryptfs_printk(KERN_ERR, "Packet length larger than "
-                               "maximum allowable\n");
                goto out;
        }
-       /* General packet header */
-       /* Packet tag */
        dest[(*packet_length)++] = ECRYPTFS_TAG_11_PACKET_TYPE;
-       /* Packet length */
        rc = write_packet_length(&dest[(*packet_length)],
-                                (13 + contents_length), &packet_size_length);
+                                (max_packet_size - 4), &packet_size_length);
        if (rc) {
-               ecryptfs_printk(KERN_ERR, "Error generating tag 11 packet "
-                               "header; cannot generate packet length\n");
+               printk(KERN_ERR "Error generating tag 11 packet header; cannot "
+                      "generate packet length. rc = [%d]\n", rc);
                goto out;
        }
        (*packet_length) += packet_size_length;
-       /* Tag 11 specific */
-       /* One-octet field that describes how the data is formatted */
-       dest[(*packet_length)++] = 0x62; /* binary data */
-       /* One-octet filename length followed by filename */
+       dest[(*packet_length)++] = 0x62; /* binary data format specifier */
        dest[(*packet_length)++] = 8;
        memcpy(&dest[(*packet_length)], "_CONSOLE", 8);
        (*packet_length) += 8;
-       /* Four-octet number indicating modification date */
        memset(&dest[(*packet_length)], 0x00, 4);
        (*packet_length) += 4;
-       /* Remainder is literal data */
        memcpy(&dest[(*packet_length)], contents, contents_length);
        (*packet_length) += contents_length;
  out:
        if (rc)
                (*packet_length) = 0;
+       else
+               (*remaining_bytes) -= (*packet_length);
        return rc;
 }