Commit 69a6a0b3 authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
Browse files

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: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7455a76f

Documentation/networking/dccp.txt

+4 −2
Original line number Diff line number Diff line
@@ -58,8 +58,10 @@ DCCP_SOCKOPT_GET_CUR_MPS is read-only and retrieves the current maximum packet 
size (application payload size) in bytes, see RFC 4340, section 14.



DCCP_SOCKOPT_AVAILABLE_CCIDS is also read-only and returns the list of CCIDs

supported by the endpoint (see include/linux/dccp.h for symbolic constants).

The caller needs to provide a sufficiently large (> 2) array of type uint8_t.

supported by the endpoint. The option value is an array of type uint8_t whose

size is passed as option length. The minimum array size is 4 elements, the

value returned in the optlen argument always reflects the true number of

built-in CCIDs.



DCCP_SOCKOPT_CCID is write-only and sets both the TX and RX CCIDs at the same

time, combining the operation of the next two socket options. This option is

net/dccp/ccid.c

+4 −5
Original line number Diff line number Diff line
@@ -63,14 +63,13 @@ int ccid_getsockopt_builtin_ccids(struct sock *sk, int len, 
	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);

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