tree-diff: catch integer overflow in combine_diff_path allocation

A combine_diff_path struct has two "flex" members allocated
alongside the struct: a string to hold the pathname, and an
array of parent pointers. We use an "int" to compute this,
meaning we may easily overflow it if the pathname is
extremely long.

We can fix this by using size_t, and checking for overflow
with the st_add helper.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/diff.h b/diff.h
index 70b2d70d64e1e47da617f51b8385870a22e92f40..beafbbdec763f9ac7fb6a41f225a97fa8d0ae580 100644 (file)
--- a/diff.h
+++ b/diff.h
@@ -222,8 +222,8 @@ struct combine_diff_path {
        } parent[FLEX_ARRAY];
 };
 #define combine_diff_path_size(n, l) \
-       (sizeof(struct combine_diff_path) + \
-        sizeof(struct combine_diff_parent) * (n) + (l) + 1)
+       st_add4(sizeof(struct combine_diff_path), (l), 1, \
+               st_mult(sizeof(struct combine_diff_parent), (n)))
 
 extern void show_combined_diff(struct combine_diff_path *elem, int num_parent,
                              int dense, struct rev_info *);

diff --git a/tree-diff.c b/tree-diff.c
index 290a1da4ce5c3504dd75e584030a4a00fbdbe9a2..4dda9a14abacbf38ba19fcf89b2ef54576a26538 100644 (file)
--- a/tree-diff.c
+++ b/tree-diff.c
@@ -124,8 +124,8 @@ static struct combine_diff_path *path_appendnew(struct combine_diff_path *last,
        unsigned mode, const unsigned char *sha1)
 {
        struct combine_diff_path *p;
-       int len = base->len + pathlen;
-       int alloclen = combine_diff_path_size(nparent, len);
+       size_t len = st_add(base->len, pathlen);
+       size_t alloclen = combine_diff_path_size(nparent, len);
 
        /* if last->next is !NULL - it is a pre-allocated memory, we can reuse */
        p = last->next;