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commit 06f7ebb1dade2f0dbf872ea2bedf17cff4734bdd
Author: Olaf Kirch <okir () suse de>
Date: Thu Aug 6 16:27:20 2015 +0200
Fix memory corruption in PMAP_CALLIT code
- A PMAP_CALLIT call comes in on IPv4 UDP
- rpcbind duplicates the caller's address to a netbuf and stores it in
FINFO[0].caller_addr. caller_addr->buf now points to a memory region A
with a size of 16 bytes
- rpcbind forwards the call to the local service, receives a reply
- when processing the reply, it does this in xprt_set_caller:
xprt->xp_rtaddr = *FINFO[0].caller_addr
It sends out the reply, and then frees the netbuf caller_addr and
caller_addr.buf.
However, it does not clear xp_rtaddr, so xp_rtaddr.buf now refers
to memory region A, which is free.
- When the next call comes in on the UDP/IPv4 socket, svc_dg_recv will
be called, which will set xp_rtaddr to the client's address.
It will reuse the buffer inside xp_rtaddr, ie it will write a
sockaddr_in to region A
Some time down the road, an incoming TCP connection is accepted,
allocating a fresh SVCXPRT. The memory region A is inside the
new SVCXPRT
- While processing the TCP call, another UDP call comes in, again
overwriting region A with the client's address
- TCP client closes connection. In svc_destroy, we now trip over
the garbage left in region A
We ran into the case where a commercial scanner was triggering
occasional rpcbind segfaults. The core file that was captured showed
a corrupted xprt->xp_netid pointer that was really a sockaddr_in.
Signed-off-by: Olaf Kirch <okir () suse de>
---
src/rpcb_svc_com.c | 23 ++++++++++++++++++++++-
1 file changed, 22 insertions(+), 1 deletion(-)
--- a/src/rpcb_svc_com.c
+++ b/src/rpcb_svc_com.c
@@ -1204,12 +1204,33 @@ check_rmtcalls(struct pollfd *pfds, int
return (ncallbacks_found);
}
+/*
+ * This is really a helper function defined in libtirpc, but unfortunately, it hasn't
+ * been exported yet.
+ */
+static struct netbuf *
+__rpc_set_netbuf(struct netbuf *nb, const void *ptr, size_t len)
+{
+ if (nb->len != len) {
+ if (nb->len)
+ mem_free(nb->buf, nb->len);
+ nb->buf = mem_alloc(len);
+ if (nb->buf == NULL)
+ return NULL;
+
+ nb->maxlen = nb->len = len;
+ }
+ memcpy(nb->buf, ptr, len);
+ return nb;
+}
+
static void
xprt_set_caller(SVCXPRT *xprt, struct finfo *fi)
{
+ const struct netbuf *caller = fi->caller_addr;
u_int32_t *xidp;
- *(svc_getrpccaller(xprt)) = *(fi->caller_addr);
+ __rpc_set_netbuf(svc_getrpccaller(xprt), caller->buf, caller->len);
xidp = __rpcb_get_dg_xidp(xprt);
*xidp = fi->caller_xid;
}
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