uml: improved error handling while locating temp dir

* arch/um/os-Linux/mem.c (make_tempfile): Don't deref NULL upon failed malloc.

* arch/um/os-Linux/mem.c (make_tempfile): Handle NULL tempdir.
Don't let a long tempdir (e.g., via TMPDIR) provoke heap corruption.

[ jdike - formatting cleanups, deleted obsolete comment ]

Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 9 deletions

diff --git a/arch/um/os-Linux/mem.c b/arch/um/os-Linux/mem.c
index 38742c21def5..93a11d7edfa0 100644
--- a/arch/um/os-Linux/mem.c
+++ b/arch/um/os-Linux/mem.c
@@ -162,11 +162,6 @@ found:
         goto out;
 }
 
-/*
- * This proc still used in tt-mode
- * (file: kernel/tt/ptproxy/proxy.c, proc: start_debugger).
- * So it isn't 'static' yet.
- */
 static int __init make_tempfile(const char *template, char **out_tempname,
                                 int do_unlink)
 {
@@ -175,10 +170,13 @@ static int __init make_tempfile(const char *template, char **out_tempname,
 
         which_tmpdir();
         tempname = malloc(MAXPATHLEN);
-        if (!tempname)
-                goto out;
+        if (tempname == NULL)
+                return -1;
 
         find_tempdir();
+        if ((tempdir == NULL) || (strlen(tempdir) >= MAXPATHLEN))
+                return -1;
+
         if (template[0] != '/')
                 strcpy(tempname, tempdir);
         else
@@ -196,9 +194,8 @@ static int __init make_tempfile(const char *template, char **out_tempname,
         }
         if (out_tempname) {
                 *out_tempname = tempname;
-        } else {
+        } else
                 free(tempname);
-        }
         return fd;
 out:
         free(tempname);