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From: Michael Tokarev <mjt@tls.msk.ru>
Date: Thu, 28 May 2015 14:12:26 +0300
Subject: [PATCH] slirp: use less predictable directory name in /tmp for smb
 config (CVE-2015-4037)

In this version I used mkdtemp(3) which is:

        _BSD_SOURCE
        || /* Since glibc 2.10: */
            (_POSIX_C_SOURCE >= 200809L || _XOPEN_SOURCE >= 700)

(POSIX.1-2008), so should be available on systems we care about.

While at it, reset the resulting directory name within smb structure
on error so cleanup function wont try to remove directory which we
failed to create.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
(cherry picked from commit 8b8f1c7e9ddb2e88a144638f6527bf70e32343e3)
---
 net/slirp.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/net/slirp.c b/net/slirp.c
index 9bbed74..3090c10 100644
--- a/net/slirp.c
+++ b/net/slirp.c
@@ -481,7 +481,6 @@ static void slirp_smb_cleanup(SlirpState *s)
 static int slirp_smb(SlirpState* s, const char *exported_dir,
                      struct in_addr vserver_addr)
 {
-    static int instance;
     char smb_conf[128];
     char smb_cmdline[128];
     struct passwd *passwd;
@@ -505,10 +504,10 @@ static int slirp_smb(SlirpState* s, const char *exported_dir,
         return -1;
     }
 
-    snprintf(s->smb_dir, sizeof(s->smb_dir), "/tmp/qemu-smb.%ld-%d",
-             (long)getpid(), instance++);
-    if (mkdir(s->smb_dir, 0700) < 0) {
+    snprintf(s->smb_dir, sizeof(s->smb_dir), "/tmp/qemu-smb.XXXXXX");
+    if (!mkdtemp(s->smb_dir)) {
         error_report("could not create samba server dir '%s'", s->smb_dir);
+        s->smb_dir[0] = 0;
         return -1;
     }
     snprintf(smb_conf, sizeof(smb_conf), "%s/%s", s->smb_dir, "smb.conf");