[PPP_MPPE]: Fix "osize too small" check.

Prevent mppe_decompress() from generating "osize too small" errors when
checking for output buffer size.  When receiving a packet of mru size the
output buffer for decrypted data is 1 byte too small since
mppe_decompress() tries to account for possible PFC, however later in code
it is assumed no PFC.

Adjusting the check prevented these errors from occurring.

Signed-off-by: Konstantin Sharlaimov <konstantin.sharlaimov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 5 deletions

diff --git a/drivers/net/ppp_mppe.c b/drivers/net/ppp_mppe.c
index d5bdd2574659..5ae80bbe2edc 100644
--- a/drivers/net/ppp_mppe.c
+++ b/drivers/net/ppp_mppe.c
@@ -493,14 +493,14 @@ mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf,
 
         /*
          * Make sure we have enough room to decrypt the packet.
-         * Note that for our test we only subtract 1 byte whereas in
-         * mppe_compress() we added 2 bytes (+MPPE_OVHD);
-         * this is to account for possible PFC.
+         * To account for possible PFC we should only subtract 1
+         * byte whereas in mppe_compress() we added 2 bytes (+MPPE_OVHD);
+         * However, we assume no PFC, thus subtracting 2 bytes.
          */
-        if (osize < isize - MPPE_OVHD - 1) {
+        if (osize < isize - MPPE_OVHD - 2) {
                 printk(KERN_DEBUG "mppe_decompress[%d]: osize too small! "
                        "(have: %d need: %d)\n", state->unit,
-                       osize, isize - MPPE_OVHD - 1);
+                       osize, isize - MPPE_OVHD - 2);
                 return DECOMP_ERROR;
         }
         osize = isize - MPPE_OVHD - 2;  /* assume no PFC */