Avoid null pointer dereference in cgit_print_diff().

When calling cgit_print_diff() with a bad new_rev and a NULL old_rev,
checking for new_rev's parent commit will result in a null pointer
dereference. Returning on an invalid commit before dereferencing fixes
this. Spotted with clang-analyzer.

Signed-off-by: Lukas Fleischer <cgit@cryptocrack.de>
Signed-off-by: Lars Hjemli <hjemli@gmail.com>

diff --git a/ui-diff.c b/ui-diff.c
index a7bc667f799cfd0e167508e90d0f5273d3c90f42..d21541bd4d2b79d19222fc9dd09ae14e70d59e51 100644 (file)
--- a/ui-diff.c
+++ b/ui-diff.c
@@ -345,8 +345,10 @@ void cgit_print_diff(const char *new_rev, const char *old_rev, const char *prefi
                return;
        }
        commit = lookup_commit_reference(new_rev_sha1);
-       if (!commit || parse_commit(commit))
+       if (!commit || parse_commit(commit)) {
                cgit_print_error(fmt("Bad commit: %s", sha1_to_hex(new_rev_sha1)));
+               return;
+       }
 
        if (old_rev)
                get_sha1(old_rev, old_rev_sha1);
@@ -362,8 +364,10 @@ void cgit_print_diff(const char *new_rev, const char *old_rev, const char *prefi
                        return;
                }
                commit2 = lookup_commit_reference(old_rev_sha1);
-               if (!commit2 || parse_commit(commit2))
+               if (!commit2 || parse_commit(commit2)) {
                        cgit_print_error(fmt("Bad commit: %s", sha1_to_hex(old_rev_sha1)));
+                       return;
+               }
        }
 
        if ((ctx.qry.ssdiff && !ctx.cfg.ssdiff) || (!ctx.qry.ssdiff && ctx.cfg.ssdiff))