[Bug libc/17542] New: conditional jump depends on uninitialised value in svc_getreq_common

["bhubbard at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17542

            Bug ID: 17542
           Summary: conditional jump depends on uninitialised value in
                    svc_getreq_common
           Product: glibc
           Version: 2.21
            Status: NEW
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: bhubbard at redhat dot com
                CC: drepper.fsp at gmail dot com

Created attachment 7888
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7888&action=edit
Proposed patch to resolve uninitialised xports in xprt_register

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.

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