[Qemu-devel] [PATCH] libcacard: fix wrong array expansion logic

[Michael Tokarev]

The currrent code in libcacard/vcard_emul_nss.c:vcard_emul_options()
has a weird bug in variable usage around expanding opts->vreader
array.

There's a helper variable, vreaderOpt, which is first needlessly
initialized to NULL, next, conditionally, only we have to expand
opts->vreader, receives array expansion from g_renew() (initially
realloc), and next, even if we don't actually perform expansion,
the value of this variable is assigned to the actual array,
opts->vreader, which was supposed to be expanded.

So, since we expand the array by READER_STEP increments, only
once in READER_STEP (=4) the code will work, in other 3/4 times
it will fail badly.

Fix this by not using this temp variable when expanding the
array, and by dropping the useless =NULL initializer too -
if it wasn't in place initially, compiler warned us about
this problem at the beginning.

Signed-off-by: Michael Tokarev <address@hidden>
---
 libcacard/vcard_emul_nss.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/libcacard/vcard_emul_nss.c b/libcacard/vcard_emul_nss.c
index b7db51d..8462aef 100644
--- a/libcacard/vcard_emul_nss.c
+++ b/libcacard/vcard_emul_nss.c
@@ -1149,7 +1149,7 @@ vcard_emul_options(const char *args)
             char type_str[100];
             VCardEmulType type;
             int count, i;
-            VirtualReaderOptions *vreaderOpt = NULL;
+            VirtualReaderOptions *vreaderOpt;
 
             args = strip(args + 5);
             if (*args != '(') {
@@ -1173,11 +1173,10 @@ vcard_emul_options(const char *args)
 
             if (opts->vreader_count >= reader_count) {
                 reader_count += READER_STEP;
-                vreaderOpt = g_renew(VirtualReaderOptions, opts->vreader,
-                                     reader_count);
+                opts->vreader = g_renew(VirtualReaderOptions, opts->vreader,
+                                        reader_count);
             }
-            opts->vreader = vreaderOpt;
-            vreaderOpt = &vreaderOpt[opts->vreader_count];
+            vreaderOpt = &opts->vreader[opts->vreader_count];
             vreaderOpt->name = g_strndup(name, name_length);
             vreaderOpt->vname = g_strndup(vname, vname_length);
             vreaderOpt->card_type = type;
-- 
1.7.10.4