[PATCH] [BZ 17542] sunrpc: conditional jump depends on uninitialised value in svc_getreq_common

[Brad Hubbard]

If xports is NULL in xprt_register we malloc it but if sock >
_rpc_dtablesize() that memory does not get initialised and may in theory
contain any value. Later we make a conditional jump in svc_getreq_common
based on the uninitialised memory and this caused a general protection
fault in rpc.statd on an older version of glibc but this code has not
changed since that version.

Following is the valgrind warning.

==26802== Conditional jump or move depends on uninitialised value(s)
==26802==    at 0x5343A25: svc_getreq_common (in /lib64/libc-2.5.so)
==26802==    by 0x534357B: svc_getreqset (in /lib64/libc-2.5.so)
==26802==    by 0x10DE1F: ??? (in /sbin/rpc.statd)
==26802==    by 0x10D0EF: main (in /sbin/rpc.statd)
==26802==  Uninitialised value was created by a heap allocation
==26802==    at 0x4C2210C: malloc (vg_replace_malloc.c:195)
==26802==    by 0x53438BE: xprt_register (in /lib64/libc-2.5.so)
==26802==    by 0x53450DF: svcudp_bufcreate (in /lib64/libc-2.5.so)
==26802==    by 0x10FE32: ??? (in /sbin/rpc.statd)
==26802==    by 0x10D13E: main (in /sbin/rpc.statd)

I believe the solution here is to change the malloc call to a calloc
call and the attached patch does that. The GPF could not be reproduced
with the patched glibc.

2014-11-05  Brad Hubbard  <bhubbard@redhat.com>

	* sunrpc/svc.c: Resolve uninitialised xports in xprt_register

---
  sunrpc/svc.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sunrpc/svc.c b/sunrpc/svc.c
index ccf0902..30c3a93 100644
--- a/sunrpc/svc.c
+++ b/sunrpc/svc.c
@@ -97,8 +97,8 @@ xprt_register (SVCXPRT *xprt)
  
    if (xports == NULL)
      {
-      xports = (SVCXPRT **) malloc (_rpc_dtablesize () * sizeof (SVCXPRT *));
-      if (xports == NULL) /* Don´t add handle */
+      xports = (SVCXPRT **) calloc (_rpc_dtablesize (), sizeof (SVCXPRT *));
+      if (xports == NULL) /* Don't add handle */
  	return;
      }