don't dereference NULL after failed strdup

Most of these are obvious NULL-deref bug fixes, for example,
the ones in these files:

  block/curl.c
  net.c
  slirp/misc.c

and the first one in block/vvfat.c.
The others in block/vvfat.c may not lead to an immediate segfault, but I
traced the two schedule_rename(..., strdup(path)) uses, and a failed
strdup would appear to trigger this assertion in handle_renames_and_mkdirs:

	    assert(commit->path);

The conversion to use qemu_strdup in envlist_to_environ is not technically
needed, but does avoid a theoretical leak in the caller when strdup fails
for one value, but later succeeds in allocating another buffer(plausible,
if one string length is much larger than the others).  The caller does
not know the length of the returned list, and as such can only free
pointers until it hits the first NULL.  If there are non-NULL pointers
beyond the first, their buffers would be leaked.  This one is admittedly
far-fetched.

The two in linux-user/main.c are worth fixing to ensure that an
OOM error is diagnosed up front, rather than letting it provoke some
harder-to-diagnose secondary error, in case of exec failure, or worse, in
case the exec succeeds but with an invalid list of command line options.
However, considering how unlikely it is to encounter a failed strdup early
in main, this isn't a big deal.  Note that adding the required uses of
qemu_strdup here and in envlist.c induce link failures because qemu_strdup
is not currently in any library they're linked with.  So for now, I've
omitted those changes, as well as the fixes in target-i386/helper.c
and target-sparc/helper.c.

If you'd like to see the above discussion (or anything else)
in the commit log, just let me know and I'll be happy to adjust.

>From 9af42864fd1ea666bd25e2cecfdfae74c20aa8c7 Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyering@redhat.com>
Date: Mon, 8 Feb 2010 18:29:29 +0100
Subject: [PATCH] don't dereference NULL after failed strdup

Handle failing strdup by replacing each use with qemu_strdup,
so as not to dereference NULL or trigger a failing assertion.
* block/curl.c (curl_open): s/\bstrdup\b/qemu_strdup/
* block/vvfat.c (init_directories): Likewise.
(get_cluster_count_for_direntry, check_directory_consistency): Likewise.
* net.c (parse_host_src_port): Likewise.
* slirp/misc.c (fork_exec): Likewise.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 6265eb26a375179f193f792e4f0d49036d2cf052)

diff --git a/block/curl.c b/block/curl.c
index 5223ce8790d9ec9438a9d33bb36828a129a83121..c9c457486db19fe1397d1cd368f3c56ca89f1e13 100644 (file)
--- a/block/curl.c
+++ b/block/curl.c
@@ -309,7 +309,7 @@ static int curl_open(BlockDriverState *bs, const char *filename, int flags)
 
     static int inited = 0;
 
-    file = strdup(filename);
+    file = qemu_strdup(filename);
     s->readahead_size = READ_AHEAD_SIZE;
 
     /* Parse a trailing ":readahead=#:" param, if present. */

diff --git a/block/vvfat.c b/block/vvfat.c
index 063f7318cf12d0046f19bdf5eeee978472d32e91..c1acb3586481b09531e2860335432970d51cc81f 100644 (file)
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -882,7 +882,7 @@ static int init_directories(BDRVVVFATState* s,
     mapping->dir_index = 0;
     mapping->info.dir.parent_mapping_index = -1;
     mapping->first_mapping_index = -1;
-    mapping->path = strdup(dirname);
+    mapping->path = qemu_strdup(dirname);
     i = strlen(mapping->path);
     if (i > 0 && mapping->path[i - 1] == '/')
        mapping->path[i - 1] = '\0';
@@ -1632,10 +1632,10 @@ static uint32_t get_cluster_count_for_direntry(BDRVVVFATState* s,
 
            /* rename */
            if (strcmp(basename, basename2))
-               schedule_rename(s, cluster_num, strdup(path));
+               schedule_rename(s, cluster_num, qemu_strdup(path));
        } else if (is_file(direntry))
            /* new file */
-           schedule_new_file(s, strdup(path), cluster_num);
+           schedule_new_file(s, qemu_strdup(path), cluster_num);
        else {
            assert(0);
            return 0;
@@ -1752,10 +1752,10 @@ static int check_directory_consistency(BDRVVVFATState *s,
        mapping->mode &= ~MODE_DELETED;
 
        if (strcmp(basename, basename2))
-           schedule_rename(s, cluster_num, strdup(path));
+           schedule_rename(s, cluster_num, qemu_strdup(path));
     } else
        /* new directory */
-       schedule_mkdir(s, cluster_num, strdup(path));
+       schedule_mkdir(s, cluster_num, qemu_strdup(path));
 
     lfn_init(&lfn);
     do {

diff --git a/net.c b/net.c
index 6ef93e615c8db9d2de230fc1b988213d763ba4f7..8e951ca9daee05d91026812ed54fd0d1d62fcad3 100644 (file)
--- a/net.c
+++ b/net.c
@@ -96,7 +96,7 @@ int parse_host_src_port(struct sockaddr_in *haddr,
                         struct sockaddr_in *saddr,
                         const char *input_str)
 {
-    char *str = strdup(input_str);
+    char *str = qemu_strdup(input_str);
     char *host_str = str;
     char *src_str;
     const char *src_str2;

diff --git a/slirp/misc.c b/slirp/misc.c
index c76ad8fefdf183c1927a3f598678da3baffee3ca..b68af6d7a0df991dd0ebd927c56541c39c324337 100644 (file)
--- a/slirp/misc.c
+++ b/slirp/misc.c
@@ -179,7 +179,7 @@ fork_exec(struct socket *so, const char *ex, int do_pty)
                   close(s);
 
                i = 0;
-               bptr = strdup(ex); /* No need to free() this */
+               bptr = qemu_strdup(ex); /* No need to free() this */
                if (do_pty == 1) {
                        /* Setup "slirp.telnetd -x" */
                        argv[i++] = "slirp.telnetd";