[glib: 1/2] galloca: Clarify alloca() sizes must always be controlled by the program

[Simon McVittie <smcv src gnome org>]

commit b657e78add09e7273a26ff4278dbc01c60b90fc1
Author: Philip Withnall <pwithnall endlessos org>
Date:   Thu Mar 25 12:55:21 2021 +0000

    galloca: Clarify alloca() sizes must always be controlled by the program
    
    To avoid security vulnerabilities.
    
    Signed-off-by: Philip Withnall <pwithnall endlessos org>
    
    Fixes: #2363

 glib/galloca.h | 11 +++++++++++
 1 file changed, 11 insertions(+)
---
diff --git a/glib/galloca.h b/glib/galloca.h
index 47151ee8b..014a0efcb 100644
--- a/glib/galloca.h
+++ b/glib/galloca.h
@@ -81,6 +81,11 @@ G_END_DECLS
  *   way as out of stack space situations from infinite function recursion, i.e.
  *   with a segmentation fault.
  *
+ * - Allowing @size to be specified by an untrusted party would allow for them
+ *   to trigger a segmentation fault by specifying a large size, leading to a
+ *   denial of service vulnerability. @size must always be entirely under the
+ *   control of the program.
+ *
  * - Special care has to be taken when mixing alloca() with GNU C variable sized arrays.
  *   Stack space allocated with alloca() in the same scope as a variable sized array
  *   will be freed together with the variable sized array upon exit of that scope, and
@@ -96,6 +101,12 @@ G_END_DECLS
  * 
  * Wraps g_alloca() in a more typesafe manner.
  * 
+ * As mentioned in the documentation for g_alloca(), @n_structs must always be
+ * entirely under the control of the program, or you may introduce a denial of
+ * service vulnerability. In addition, the multiplication of @struct_type by
+ * @n_structs is not checked, so an overflow may lead to a remote code execution
+ * vulnerability.
+ *
  * Returns: Pointer to stack space for @n_structs chunks of type @struct_type
  */
 #define g_newa(struct_type, n_structs) ((struct_type*) g_alloca (sizeof (struct_type) * (gsize) (n_structs)))