wireshark: Don't leak column strings

One of the problems of using val_to_str() is that it may return a
const string from given table ('vs'), OR return an allocated one.
Since the caller has no idea which case it is, it resides to safe
option and don't free returned string. But that might lead to a
memleak. This behaviour is fixed with wireshark-4.6.0 and support
for it will be introduced soon. But first, make vir_val_to_str()
behave like fixed val_to_str() from newer wireshark: just always
allocate the string.

Now, if val_to_str() needs to allocate new memory it obtains
allocator by calling wmem_packet_scope() which is what we may do
too.

Hand in hand with that, we need to free the memory using the
correct allocator, hence wmem_free(). But let's put it into a
wrapper vir_wmem_free() because just like val_to_str(), it'll
need additional argument when adapting to new wireshark.

Oh, and freeing the memory right after col_add_fstr() is safe as
it uses vsnprintf() under the hood to format passed args.

One last thing, the wmem.h file used to live under epan/wmem/ but
then in v3.5.0~240 [1] was moved to wsutil/wmem/.

1: https://gitlab.com/wireshark/wireshark/-/commit/7f9c1f5f92c131354fc8b2b88d473706786064c0
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>

diff --git a/meson.build b/meson.build
index bcc18b20e5b11344ed994b4061e3d4b7af52c5b8..a1e0e5ecd5240e04eb87d6ba3f5211fe942bd8d2 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -1365,6 +1365,26 @@ if wireshark_dep.found()
   if cc.check_header('wireshark/ws_version.h')
     conf.set('WITH_WS_VERSION', 1)
   endif
+
+  # Find wmem.h
+  # But it's not as easy as you'd think. Ubuntu 20.04 has split parts of
+  # libwireshark.so into libwsutil.so but:
+  # a) wireshark.pc never mentions it,
+  # b) libwsutil-dev package doesn't install pkg-config file.
+  # Fortunately, it's fixed in 24.04.
+  if cc.check_header('wireshark/epan/wmem/wmem.h', dependencies: wireshark_dep)
+    conf.set('WITH_WS_EPAN_WMEM', 1)
+  elif cc.check_header('wireshark/wsutil/wmem/wmem.h', dependencies: wireshark_dep)
+    conf.set('WITH_WS_WSUTIL_WMEM', 1)
+  else
+    error('Unable to locate wmem.h file')
+  endif
+
+  # TODO: drop wsutil dep once support for Ubuntu 20.04 is dropped
+  wsutil_dep = dependency('', required: false)
+  if not cc.has_function('wmem_free', dependencies: wireshark_dep)
+    wsutil_dep = cc.find_library('wsutil', required: true)
+  endif
 endif
 
 # generic build dependencies checks

diff --git a/tools/wireshark/src/meson.build b/tools/wireshark/src/meson.build
index 9b452dc5ca7d194a7d3e0e7bd68fd8aa9cf714c0..ba0df913e06f27e6511c24edd292e3956c532018 100644 (file)
--- a/tools/wireshark/src/meson.build
+++ b/tools/wireshark/src/meson.build
@@ -9,6 +9,7 @@ shared_library(
   ],
   dependencies: [
     wireshark_dep,
+    wsutil_dep,
     xdr_dep,
     tools_dep,
   ],

diff --git a/tools/wireshark/src/packet-libvirt.c b/tools/wireshark/src/packet-libvirt.c
index f6ad2c4578d4566431b1f2ade2af6657d5ceb98b..3178ac6f27d43bb2434f1fa54ed3ac6db4da8da4 100644 (file)
--- a/tools/wireshark/src/packet-libvirt.c
+++ b/tools/wireshark/src/packet-libvirt.c
@@ -21,6 +21,11 @@
 #include <wireshark/epan/proto.h>
 #include <wireshark/epan/packet.h>
 #include <wireshark/epan/dissectors/packet-tcp.h>
+#ifdef WITH_WS_EPAN_WMEM
+# include <wireshark/epan/wmem/wmem.h>
+#elif WITH_WS_WSUTIL_WMEM
+# include <wireshark/wsutil/wmem/wmem.h>
+#endif
 #include <rpc/types.h>
 #include <rpc/xdr.h>
 #include "packet-libvirt.h"
@@ -140,13 +145,19 @@ static const value_string status_strings[] = {
     { -1, NULL }
 };
 
-static const char *
+static char *
 G_GNUC_PRINTF(3, 0)
 vir_val_to_str(const uint32_t val,
                const value_string *vs,
                const char *fmt)
 {
-    return val_to_str(val, vs, fmt);
+    return val_to_str_wmem(wmem_packet_scope(), val, vs, fmt);
+}
+
+static void
+vir_wmem_free(void *ptr)
+{
+    wmem_free(wmem_packet_scope(), ptr);
 }
 
 static gboolean
@@ -462,6 +473,10 @@ dissect_libvirt_message(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
     uint32_t prog, serial;
     int32_t proc, type, status;
     const value_string *vs;
+    char *prog_str = NULL;
+    char *proc_str = NULL;
+    char *type_str = NULL;
+    char *status_str = NULL;
 
     col_set_str(pinfo->cinfo, COL_PROTOCOL, "Libvirt");
     col_clear(pinfo->cinfo, COL_INFO);
@@ -474,15 +489,21 @@ dissect_libvirt_message(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
     serial = tvb_get_ntohl(tvb, offset); offset += 4;
     status = tvb_get_ntohil(tvb, offset); offset += 4;
 
-    col_add_fstr(pinfo->cinfo, COL_INFO, "Prog=%s",
-                 vir_val_to_str(prog, program_strings, "%x"));
+    prog_str = vir_val_to_str(prog, program_strings, "%x");
+    col_add_fstr(pinfo->cinfo, COL_INFO, "Prog=%s", prog_str);
+    vir_wmem_free(prog_str);
 
     vs = get_program_data(prog, VIR_PROGRAM_PROCSTRINGS);
-    col_append_fstr(pinfo->cinfo, COL_INFO, " Proc=%s", vir_val_to_str(proc, vs, "%d"));
+    proc_str = vir_val_to_str(proc, vs, "%d");
+    col_append_fstr(pinfo->cinfo, COL_INFO, " Proc=%s", proc_str);
+    vir_wmem_free(proc_str);
 
+    type_str = vir_val_to_str(type, type_strings, "%d");
+    status_str = vir_val_to_str(status, status_strings, "%d");
     col_append_fstr(pinfo->cinfo, COL_INFO, " Type=%s Serial=%u Status=%s",
-                    vir_val_to_str(type, type_strings, "%d"), serial,
-                    vir_val_to_str(status, status_strings, "%d"));
+                    type_str, serial, status_str);
+    vir_wmem_free(status_str);
+    vir_wmem_free(type_str);
 
     if (tree) {
         gint *hf_proc;