harden realloc/free to detect simple overflows

[musl] / src / malloc / malloc.c

diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c
index 1a6d149..4044eb2 100644 (file)
--- a/src/malloc/malloc.c
+++ b/src/malloc/malloc.c
@@ -418,6 +418,9 @@ void *realloc(void *p, size_t n)
 
        next = NEXT_CHUNK(self);
 
+       /* Crash on corrupted footer (likely from buffer overflow) */
+       if (next->psize != self->csize) a_crash();
+
        /* Merge adjacent chunks if we need more space. This is not
         * a waste of time even if we fail to get enough space, because our
         * subsequent call to free would otherwise have to do the merge. */
@@ -471,6 +474,9 @@ void free(void *p)
        final_size = new_size = CHUNK_SIZE(self);
        next = NEXT_CHUNK(self);
 
+       /* Crash on corrupted footer (likely from buffer overflow) */
+       if (next->psize != self->csize) a_crash();
+
        for (;;) {
                /* Replace middle of large chunks with fresh zero pages */
                if (reclaim && (self->psize & next->csize & C_INUSE)) {