@@ -1380,7 +1380,7 @@ static inline struct sctp_endpoint *sctp_ep(struct sctp_ep_common *base)
struct sctp_endpoint *sctp_endpoint_new(struct sock *, gfp_t);
void sctp_endpoint_free(struct sctp_endpoint *);
void sctp_endpoint_put(struct sctp_endpoint *);
-void sctp_endpoint_hold(struct sctp_endpoint *);
+struct sctp_endpoint *sctp_endpoint_hold(struct sctp_endpoint *);
void sctp_endpoint_add_asoc(struct sctp_endpoint *, struct sctp_association *);
struct sctp_association *sctp_endpoint_lookup_assoc(
const struct sctp_endpoint *ep,
@@ -222,10 +222,12 @@ static void sctp_endpoint_destroy(struct sctp_endpoint *ep)
}
/* Hold a reference to an endpoint. */
-void sctp_endpoint_hold(struct sctp_endpoint *ep)
+struct sctp_endpoint *sctp_endpoint_hold(struct sctp_endpoint *ep)
{
refcount_inc(&ep->base.refcnt);
+ return ep;
}
+EXPORT_SYMBOL_GPL(sctp_endpoint_hold);
/* Release a reference to an endpoint and clean up if there are
* no more references.
@@ -235,6 +237,7 @@ void sctp_endpoint_put(struct sctp_endpoint *ep)
if (refcount_dec_and_test(&ep->base.refcnt))
sctp_endpoint_destroy(ep);
}
+EXPORT_SYMBOL_GPL(sctp_endpoint_put);
/* Is this the endpoint we are looking for? */
struct sctp_endpoint *sctp_endpoint_is_match(struct sctp_endpoint *ep,
net/sctp/diag.c for instance is built into its own separate module (sctp_diag.ko) and requires the use of sctp_endpoint_{hold,put}() in order to prevent a recently found use-after-free issue. In order to prevent data corruption of the pointer used to take a reference on a specific endpoint, between the time of calling sctp_endpoint_hold() and it returning, the API now returns a pointer to the exact endpoint that was incremented. For example, in sctp_sock_dump(), we could have the following hunk: sctp_endpoint_hold(tsp->asoc->ep); ep = tsp->asoc->ep; sk = ep->base.sk lock_sock(ep->base.sk); It is possible for this task to be swapped out immediately following the call into sctp_endpoint_hold() that would change the address of tsp->asoc->ep to point to a completely different endpoint. This means a reference could be taken to the old endpoint and the new one would be processed without a reference taken, moreover the new endpoint could then be freed whilst still processing as a result, causing a use-after-free. If we return the exact pointer that was held, we ensure this task processes only the endpoint we have taken a reference to. The resultant hunk now looks like this: ep = sctp_endpoint_hold(tsp->asoc->ep); sk = ep->base.sk lock_sock(sk); Cc: Vlad Yasevich <vyasevich@gmail.com> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Jakub Kicinski <kuba@kernel.org> Cc: lksctp developers <linux-sctp@vger.kernel.org> Cc: "H.P. Yarroll" <piggy@acm.org> Cc: Karl Knutson <karl@athena.chicago.il.us> Cc: Jon Grimm <jgrimm@us.ibm.com> Cc: Xingang Guo <xingang.guo@intel.com> Cc: Hui Huang <hui.huang@nokia.com> Cc: Sridhar Samudrala <sri@us.ibm.com> Cc: Daisy Chang <daisyc@us.ibm.com> Cc: Ryan Layer <rmlayer@us.ibm.com> Cc: Kevin Gao <kevin.gao@intel.com> Cc: linux-sctp@vger.kernel.org Cc: netdev@vger.kernel.org Cc: stable@vger.kernel.org Fixes: 8f840e47f190c ("sctp: add the sctp_diag.c file") Signed-off-by: Lee Jones <lee.jones@linaro.org> --- include/net/sctp/structs.h | 2 +- net/sctp/endpointola.c | 5 ++++- 2 files changed, 5 insertions(+), 2 deletions(-)