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Re: [PATCH v3 02/28] glib-compat: Introduce g_memdup2() wrapper


From: Laurent Vivier
Subject: Re: [PATCH v3 02/28] glib-compat: Introduce g_memdup2() wrapper
Date: Fri, 17 Dec 2021 11:55:21 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0

Le 03/09/2021 à 19:44, Philippe Mathieu-Daudé a écrit :
When experimenting raising GLIB_VERSION_MIN_REQUIRED to 2.68
(Fedora 34 provides GLib 2.68.1) we get:

   hw/virtio/virtio-crypto.c:245:24: error: 'g_memdup' is deprecated: Use 
'g_memdup2' instead [-Werror,-Wdeprecated-declarations]
   ...

g_memdup() has been updated by g_memdup2() to fix eventual security
issues (size argument is 32-bit and could be truncated / wrapping).
GLib recommends to copy their static inline version of g_memdup2():
https://discourse.gnome.org/t/port-your-module-from-g-memdup-to-g-memdup2-now/5538

Our glib-compat.h provides a comment explaining how to deal with
these deprecated declarations (see commit e71e8cc0355
"glib: enforce the minimum required version and warn about old APIs").

Following this comment suggestion, implement the g_memdup2_qemu()
wrapper to g_memdup2(), and use the safer equivalent inlined when
we are using pre-2.68 GLib.

Reported-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
  include/glib-compat.h | 37 +++++++++++++++++++++++++++++++++++++
  1 file changed, 37 insertions(+)

diff --git a/include/glib-compat.h b/include/glib-compat.h
index 9e95c888f54..8d01a8c01fb 100644
--- a/include/glib-compat.h
+++ b/include/glib-compat.h
@@ -68,6 +68,43 @@
   * without generating warnings.
   */
+/*
+ * g_memdup2_qemu:
+ * @mem: (nullable): the memory to copy.
+ * @byte_size: the number of bytes to copy.
+ *
+ * Allocates @byte_size bytes of memory, and copies @byte_size bytes into it
+ * from @mem. If @mem is %NULL it returns %NULL.
+ *
+ * This replaces g_memdup(), which was prone to integer overflows when
+ * converting the argument from a #gsize to a #guint.
+ *
+ * This static inline version is a backport of the new public API from
+ * GLib 2.68, kept internal to GLib for backport to older stable releases.
+ * See https://gitlab.gnome.org/GNOME/glib/-/issues/2319.
+ *
+ * Returns: (nullable): a pointer to the newly-allocated copy of the memory,
+ *          or %NULL if @mem is %NULL.
+ */
+static inline gpointer g_memdup2_qemu(gconstpointer mem, gsize byte_size)
+{
+#if GLIB_CHECK_VERSION(2, 68, 0)
+    return g_memdup2(mem, byte_size);
+#else
+    gpointer new_mem;
+
+    if (mem && byte_size != 0) {
+        new_mem = g_malloc(byte_size);
+        memcpy(new_mem, mem, byte_size);
+    } else {
+        new_mem = NULL;
+    }
+
+    return new_mem;
+#endif
+}
+#define g_memdup2(m, s) g_memdup2_qemu(m, s)
+
  #if defined(G_OS_UNIX)
  /*
   * Note: The fallback implementation is not MT-safe, and it returns a copy of


Applied to my trivial-patches branch.

Thanks,
Laurent




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