On 02/27/2013 03:22 PM, Guenter Roeck wrote:
On Wed, Feb 27, 2013 at 03:09:31PM -0500, Neil Horman wrote:
On Wed, Feb 27, 2013 at 11:43:51AM -0800, Guenter Roeck wrote:
Building sctp may fail with:
In function ‘copy_from_user’,
inlined from ‘sctp_getsockopt_assoc_stats’ at
net/sctp/socket.c:5656:20:
arch/x86/include/asm/uaccess_32.h:211:26: error: call to
‘copy_from_user_overflow’ declared with attribute error: copy_from_user()
buffer size is not provably correct
if built with W=1 due to a missing parameter size validation.
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
net/sctp/socket.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index cedd9bf..0a5f2bf 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -5652,6 +5652,8 @@ static int sctp_getsockopt_assoc_stats(struct sock *sk, int len,
/* User must provide at least the assoc id */
if (len < sizeof(sctp_assoc_t))
return -EINVAL;
+ if (len > sizeof(struct sctp_assoc_stats))
+ len = sizeof(struct sctp_assoc_stats);
if (copy_from_user(&sas, optval, len))
return -EFAULT;
--
1.7.9.7
Theres more than that going on here. This will fix the warning, but the
function is written such that, if you pass in a size that is greater than the
size of a struct sctp_association, but less than a struct sctp_assoc_stats. I'm
not sure that a partial stat struct is really that useful to people. What if
you were to check for max(struct sctp_association, struct sctp_assoc_stats) as
your minimum length check, then just did a copy_from_user of that length. It
would save you having to compute two lengths separately, since you could then
just do a copy_to_user(...,sizeof(struct sctp_assoc_stats), at the bottom of
that function.
Yes, but that would require input from someone who knows the code. All I am trying
to accomplish is to ensure that copy_from_user does not overwrite the stack.
The function already has the following in it:
/* Allow the struct to grow and fill in as much as possible */
len = min_t(size_t, len, sizeof(sas));
It would be better to move that up to before the copy_from_user.
The alternative would be to do:
if (copy_from_user(&sas, optval, sizeof(sctp_assoc_t))
since all we are after here is an association id and nothing else.
-vlad
Thanks,
Guenter
--
To unsubscribe from this list: send the line "unsubscribe linux-sctp" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
