[PATCH 1/2] sock: fix bitwise OR operation short circuit

[JingPiao Chen]

sock.c: 150

150         if (syserror(tcp) || umove(tcp, addr, &ifc) < 0) {
151                 if (ifc.ifc_buf)
152                         tprints("}");
153                 else
154                         printaddr(addr);
155                 return RVAL_DECODED | 1;
156         }

Second enter function decode_ifconf(), if syserror(tcp) is true,
variable ifc is garbage value. "if (ifc.ifc_buf)" may be wrong.
example:

int main(void)
{
struct ifconf ifc;
ioctl(-1, SIOCGIFCONF, &ifc);
return 0;
}
strace -eioctl output:
ioctl(-1, SIOCGIFCONF, {41958240x7ffc354f9bc0) = -1 EBADF (Bad file
descriptor)

>From 5b2d4f12d61e5a03212de948508e830c9aeeef87 Mon Sep 17 00:00:00 2001
From: JingPiao Chen <chenjingpiao at gmail.com>
Date: Mon, 19 Dec 2016 23:08:09 +0800
Subject: [PATCH 1/2] sock: fix bitwise OR operation short circuit

* sock.c (decode_ifconf): Exchange the place of syserror() and umove().
---
 sock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sock.c b/sock.c
index cf13896..0bdb7a9 100644
--- a/sock.c
+++ b/sock.c
@@ -147,7 +147,7 @@ decode_ifconf(struct tcb *tcp, const long addr)
  return 1;
  }

- if (syserror(tcp) || umove(tcp, addr, &ifc) < 0) {
+ if (umove(tcp, addr, &ifc) < 0 || syserror(tcp)) {
  if (ifc.ifc_buf)
  tprints("}");
  else
-- 
2.7.4
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