dccp: allow probing of CCID-array length
This fixes a problem in the DCCP getsockopt() API: currently there is no way
for a user to a priori know the number of built-in CCIDs, other than trying
DCCP_SOCKOPT_AVAILABLE_CCIDS in a loop, incrementing the option length until
EINVAL is no longer returned.
This patch truncates the array to the user-provided length. No copy is made
when the length is <= 0.
Due to the length restriction in do_dccp_getsockopt() to sizeof(int), the
minimum array length remains 4, which is a reasonable default (only 3
CCIDs, CCID-2..4, are currently defined).
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ccid.c b/net/dccp/ccid.c
index ff16e9d..49d27c5 100644
--- a/net/dccp/ccid.c
+++ b/net/dccp/ccid.c
@@ -63,14 +63,13 @@
u8 *ccid_array, array_len;
int err = 0;
- if (len < ARRAY_SIZE(ccids))
- return -EINVAL;
-
if (ccid_get_builtin_ccids(&ccid_array, &array_len))
return -ENOBUFS;
- if (put_user(array_len, optlen) ||
- copy_to_user(optval, ccid_array, array_len))
+ if (put_user(array_len, optlen))
+ err = -EFAULT;
+ else if (len > 0 && copy_to_user(optval, ccid_array,
+ len > array_len ? array_len : len))
err = -EFAULT;
kfree(ccid_array);