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. 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
