builtin/revert.c: don't dereference a NULL pointer

cherry-pick will segfault when transplanting a root commit if the --ff
option is used.  This happens because the "parent" pointer is set to NULL
when the commit being cherry-picked has no parents.  Later, when "parent"
is dereferenced, the cherry-pick segfaults.

Fix this by checking whether "parent" is NULL before dereferencing it and
add a test for this case of cherry-picking a root commit with --ff.

Reported-by: Zbyszek Szmek <zbyszek@in.waw.pl>
Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/revert.c b/builtin/revert.c
index 4b47ace36b51566acb5b748f679070f02cbbf568..57b51e4a0e148062e1945d640b81559d65e4c2ba 100644 (file)
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -442,7 +442,7 @@ static int do_pick_commit(void)
        else
                parent = commit->parents->item;
 
-       if (allow_ff && !hashcmp(parent->object.sha1, head))
+       if (allow_ff && parent && !hashcmp(parent->object.sha1, head))
                return fast_forward_to(commit->object.sha1, head);
 
        if (parent && parse_commit(parent) < 0)

diff --git a/t/t3506-cherry-pick-ff.sh b/t/t3506-cherry-pick-ff.sh
index e17ae712b1078333fa191b97764177016bc01b84..51ca391e472441d2d503e721795d609bfaad1100 100755 (executable)
--- a/t/t3506-cherry-pick-ff.sh
+++ b/t/t3506-cherry-pick-ff.sh
@@ -95,4 +95,14 @@ test_expect_success 'cherry pick a merge relative to nonexistent parent with --f
        test_must_fail git cherry-pick --ff -m 3 C
 '
 
+test_expect_success 'cherry pick a root commit with --ff' '
+       git reset --hard first -- &&
+       git rm file1 &&
+       echo first >file2 &&
+       git add file2 &&
+       git commit --amend -m "file2" &&
+       git cherry-pick --ff first &&
+       test "$(git rev-parse --verify HEAD)" = "1df192cd8bc58a2b275d842cede4d221ad9000d1"
+'
+
 test_done