In reallocf(3), free the memory only when size != 0. Otherwise, when the

System V compatibility option (malloc "V" flag) is in effect a zero sized
reallocf() could cause a double free.

PR:		bin/141753
Submitted by:	Dan Lukes

1 files changed, 8 insertions, 1 deletions

diff --git a/lib/libc/stdlib/reallocf.c b/lib/libc/stdlib/reallocf.c
index 5320926..a85b5a3 100644
--- a/lib/libc/stdlib/reallocf.c
+++ b/lib/libc/stdlib/reallocf.c
@@ -35,7 +35,14 @@ reallocf(void *ptr, size_t size)
 	void *nptr;
 
 	nptr = realloc(ptr, size);
-	if (!nptr && ptr)
+
+	/*
+	 * When the System V compatibility option (malloc "V" flag) is
+	 * in effect, realloc(ptr, 0) frees the memory and returns NULL.
+	 * So, to avoid double free, call free() only when size != 0.
+	 * realloc(ptr, 0) can't fail when ptr != NULL.
+	 */
+	if (!nptr && ptr && size != 0)
 		free(ptr);
 	return (nptr);
 }