Re: [PATCH] Fixing segmentation fault when merging FETCH_HEAD

["Jose Ivan B. Vilarouca Filho" <joseivan@lavid.ufpb.br>]

From: "Jose Ivan B. Vilarouca Filho" <joseivan@lavid.ufpb.br>

Hello, Eric.

Thanks for suggestions. I've added a test in commit replacing git fetch origin by a fake FETCH_HEAD content.

merge: don't dereference NULL pointer

A segmentaion fault is raised when trying to merge FETCH_HEAD
formed only by "not-for-merge" refs.

Ex:
    git init .
    git remote add origin ...
    git fetch origin
    git merge FETCH_HEAD

Signed-off-by: Jose Ivan B. Vilarouca Filho <joseivan@lavid.ufpb.br>
---
 builtin/merge.c         |    4 ++--
 test-merge-fetchhead.sh |   23 +++++++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100755 test-merge-fetchhead.sh

diff --git a/builtin/merge.c b/builtin/merge.c
index 101ffef..098aa8a 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -1270,9 +1270,9 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 			    "an empty head"));
 		remoteheads = collect_parents(head_commit, &head_subsumed,
 					      argc, argv, NULL);
-		remote_head = remoteheads->item;
-		if (!remote_head)
+		if (!remoteheads || !remoteheads->item)
 			die(_("%s - not something we can merge"), argv[0]);
+		remote_head = remoteheads->item;
 		if (remoteheads->next)
 			die(_("Can merge only exactly one commit into empty head"));
 		read_empty(remote_head->object.oid.hash, 0);
diff --git a/test-merge-fetchhead.sh b/test-merge-fetchhead.sh
new file mode 100755
index 0000000..383415a
--- /dev/null
+++ b/test-merge-fetchhead.sh
@@ -0,0 +1,23 @@
+#!/bin/bash
+GIT=$(pwd)/git
+REPO_DIR=./test-fetch-head-repo
+
+if [ ! -x "${GIT}" ]; then
+    echo "Missing git binary"
+    exit 1
+fi
+
+${GIT} init ${REPO_DIR} || rm -rf ${REPO_DIR} || exit 1
+pushd ${REPO_DIR} || rm -rf ${REPO_DIR} || exit 1
+#Let's fake a FETCH_HEAD only formed by not-for-merge (git fetch origin)
+echo -ne "f954fc9919c9ec33179e11aa1af562384677e174\tnot-for-merge\tbranch 'master' of https://github.com/git/git.git" > .git/FETCH_HEAD
+${GIT} merge FETCH_HEAD
+GRET=$?
+popd
+if [ ${GRET} -eq 139 ]; then
+    rm -rf ${REPO_DIR}
+    exit 1
+fi
+
+rm -rf ${REPO_DIR}
+exit 0
-- 
1.7.10.4