From: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
It has been reported that "git rebase --rebase-merges" can create
corrupted reflog entries like
e9c962f2ea0 HEAD@{8}: <binary>�: Merged in <branch> (pull request #4441)
This is due to a use-after-free bug that happens because
reflog_message() uses a static `struct strbuf` and is not called to
update the current reflog message stored in `ctx->reflog_message` when
creating the merge. This means `ctx->reflog_message` points to a stale
reflog message that has been freed by subsequent call to
reflog_message() by a command such as `reset` that used the return value
directly rather than storing the result in `ctx->reflog_message`.
Fix this by creating the reflog message nearer to where the commit is
created and storing it in a local variable which is passed as an
additional parameter to run_git_commit() rather than storing the message
in `struct replay_ctx`. This makes it harder to forget to call
`reflog_message()` before creating a commit and using a variable with a
narrower scope means that a stale value cannot carried across a from one
iteration of the loop to the next which should prevent any similar
use-after-free bugs in the future.
A existing test is modified to demonstrate that merges are now created
with the correct reflog message.
Reported-by: Kristoffer Haugsbakk <code@xxxxxxxxxxxxxxx>
Signed-off-by: Phillip Wood <phillip.wood@xxxxxxxxxxxxx>
---
sequencer.c | 50 +++++++++++++++++++---------------------
t/t3430-rebase-merges.sh | 11 ++++++++-
2 files changed, 34 insertions(+), 27 deletions(-)
diff --git a/sequencer.c b/sequencer.c
index bb4667190db1..e23708690900 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -224,11 +224,6 @@ struct replay_ctx {
* current chain.
*/
struct strbuf current_fixups;
- /*
- * Stores the reflog message that will be used when creating a
- * commit. Points to a static buffer and should not be free()'d.
- */
- const char *reflog_message;
/*
* The number of completed fixup and squash commands in the
* current chain.
@@ -1124,10 +1119,10 @@ static int run_command_silent_on_success(struct child_process *cmd)
* author metadata.
*/
static int run_git_commit(const char *defmsg,
+ const char *reflog_action,
struct replay_opts *opts,
unsigned int flags)
{
- struct replay_ctx *ctx = opts->ctx;
struct child_process cmd = CHILD_PROCESS_INIT;
if ((flags & CLEANUP_MSG) && (flags & VERBATIM_MSG))
@@ -1145,7 +1140,7 @@ static int run_git_commit(const char *defmsg,
gpg_opt, gpg_opt);
}
- strvec_pushf(&cmd.env, GIT_REFLOG_ACTION "=%s", ctx->reflog_message);
+ strvec_pushf(&cmd.env, GIT_REFLOG_ACTION "=%s", reflog_action);
if (opts->committer_date_is_author_date)
strvec_pushf(&cmd.env, "GIT_COMMITTER_DATE=%s",
@@ -1529,10 +1524,10 @@ static int parse_head(struct repository *r, struct commit **head)
*/
static int try_to_commit(struct repository *r,
struct strbuf *msg, const char *author,
+ const char *reflog_action,
struct replay_opts *opts, unsigned int flags,
struct object_id *oid)
{
- struct replay_ctx *ctx = opts->ctx;
struct object_id tree;
struct commit *current_head = NULL;
struct commit_list *parents = NULL;
@@ -1694,7 +1689,7 @@ static int try_to_commit(struct repository *r,
goto out;
}
- if (update_head_with_reflog(current_head, oid, ctx->reflog_message,
+ if (update_head_with_reflog(current_head, oid, reflog_action,
msg, &err)) {
res = error("%s", err.buf);
goto out;
@@ -1725,6 +1720,7 @@ static int write_rebase_head(struct object_id *oid)
static int do_commit(struct repository *r,
const char *msg_file, const char *author,
+ const char *reflog_action,
struct replay_opts *opts, unsigned int flags,
struct object_id *oid)
{
@@ -1740,7 +1736,7 @@ static int do_commit(struct repository *r,
msg_file);
res = try_to_commit(r, msg_file ? &sb : NULL,
- author, opts, flags, &oid);
+ author, reflog_action, opts, flags, &oid);
strbuf_release(&sb);
if (!res) {
refs_delete_ref(get_main_ref_store(r), "",
@@ -1756,7 +1752,7 @@ static int do_commit(struct repository *r,
if (is_rebase_i(opts) && oid)
if (write_rebase_head(oid))
return -1;
- return run_git_commit(msg_file, opts, flags);
+ return run_git_commit(msg_file, reflog_action, opts, flags);
}
return res;
@@ -2269,13 +2265,19 @@ static int do_pick_commit(struct repository *r,
const char *msg_file = should_edit(opts) ? NULL : git_path_merge_msg(r);
struct object_id head;
struct commit *base, *next, *parent;
- const char *base_label, *next_label;
+ const char *base_label, *next_label, *reflog_action;
char *author = NULL;
struct commit_message msg = { NULL, NULL, NULL, NULL };
int res, unborn = 0, reword = 0, allow, drop_commit;
enum todo_command command = item->command;
struct commit *commit = item->commit;
+ if (is_rebase_i(opts))
+ reflog_action = reflog_message(
+ opts, command_to_string(item->command), NULL);
+ else
+ reflog_action = sequencer_reflog_action(opts);
+
if (opts->no_commit) {
/*
* We do not intend to commit immediately. We just want to
@@ -2527,7 +2529,8 @@ static int do_pick_commit(struct repository *r,
} /* else allow == 0 and there's nothing special to do */
if (!opts->no_commit && !drop_commit) {
if (author || command == TODO_REVERT || (flags & AMEND_MSG))
- res = do_commit(r, msg_file, author, opts, flags,
+ res = do_commit(r, msg_file, author, reflog_action,
+ opts, flags,
commit? &commit->object.oid : NULL);
else
res = error(_("unable to parse commit author"));
@@ -2542,7 +2545,7 @@ fast_forward_edit:
* got here.
*/
flags = EDIT_MSG | VERIFY_MSG | AMEND_MSG | ALLOW_EMPTY;
- res = run_git_commit(NULL, opts, flags);
+ res = run_git_commit(NULL, reflog_action, opts, flags);
*check_todo = 1;
}
}
@@ -4089,6 +4092,7 @@ static int do_merge(struct repository *r,
int merge_arg_len, oneline_offset, can_fast_forward, ret, k;
static struct lock_file lock;
const char *p;
+ const char *reflog_action = reflog_message(opts, "merge", NULL);
if (repo_hold_locked_index(r, &lock, LOCK_REPORT_ON_ERROR) < 0) {
ret = -1;
@@ -4360,14 +4364,15 @@ static int do_merge(struct repository *r,
* value (a negative one would indicate that the `merge`
* command needs to be rescheduled).
*/
- ret = !!run_git_commit(git_path_merge_msg(r), opts,
- run_commit_flags);
+ ret = !!run_git_commit(git_path_merge_msg(r), reflog_action,
+ opts, run_commit_flags);
if (!ret && flags & TODO_EDIT_MERGE_MSG) {
fast_forward_edit:
*check_todo = 1;
run_commit_flags |= AMEND_MSG | EDIT_MSG | VERIFY_MSG;
- ret = !!run_git_commit(NULL, opts, run_commit_flags);
+ ret = !!run_git_commit(NULL, reflog_action, opts,
+ run_commit_flags);
}
@@ -4882,13 +4887,9 @@ static int pick_one_commit(struct repository *r,
struct replay_opts *opts,
int *check_todo, int* reschedule)
{
- struct replay_ctx *ctx = opts->ctx;
int res;
struct todo_item *item = todo_list->items + todo_list->current;
const char *arg = todo_item_get_arg(todo_list, item);
- if (is_rebase_i(opts))
- ctx->reflog_message = reflog_message(
- opts, command_to_string(item->command), NULL);
res = do_pick_commit(r, item, opts, is_final_fixup(todo_list),
check_todo);
@@ -4947,7 +4948,6 @@ static int pick_commits(struct repository *r,
struct replay_ctx *ctx = opts->ctx;
int res = 0, reschedule = 0;
- ctx->reflog_message = sequencer_reflog_action(opts);
if (opts->allow_ff)
ASSERT(!(opts->signoff || opts->no_commit ||
opts->record_origin || should_edit(opts) ||
@@ -5208,6 +5208,7 @@ static int commit_staged_changes(struct repository *r,
unsigned int flags = ALLOW_EMPTY | EDIT_MSG;
unsigned int final_fixup = 0, is_clean;
struct strbuf rev = STRBUF_INIT;
+ const char *reflog_action = reflog_message(opts, "continue", NULL);
int ret;
if (has_unstaged_changes(r, 1)) {
@@ -5370,7 +5371,7 @@ static int commit_staged_changes(struct repository *r,
}
if (run_git_commit(final_fixup ? NULL : rebase_path_message(),
- opts, flags)) {
+ reflog_action, opts, flags)) {
ret = error(_("could not commit staged changes."));
goto out;
}
@@ -5402,7 +5403,6 @@ out:
int sequencer_continue(struct repository *r, struct replay_opts *opts)
{
- struct replay_ctx *ctx = opts->ctx;
struct todo_list todo_list = TODO_LIST_INIT;
int res;
@@ -5423,7 +5423,6 @@ int sequencer_continue(struct repository *r, struct replay_opts *opts)
unlink(rebase_path_dropped());
}
- ctx->reflog_message = reflog_message(opts, "continue", NULL);
if (commit_staged_changes(r, opts, &todo_list)) {
res = -1;
goto release_todo_list;
@@ -5475,7 +5474,6 @@ static int single_pick(struct repository *r,
TODO_PICK : TODO_REVERT;
item.commit = cmit;
- opts->ctx->reflog_message = sequencer_reflog_action(opts);
return do_pick_commit(r, &item, opts, 0, &check_todo);
}
diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
index b84d68c4b96b..ff81adab8cf6 100755
--- a/t/t3430-rebase-merges.sh
+++ b/t/t3430-rebase-merges.sh
@@ -86,7 +86,7 @@ test_expect_success 'create completely different structure' '
test_config sequence.editor \""$PWD"/replace-editor.sh\" &&
test_tick &&
git rebase -i -r A main &&
- test_cmp_graph <<-\EOF
+ test_cmp_graph <<-\EOF &&
* Merge the topic branch '\''onebranch'\''
|\
| * D
@@ -99,6 +99,15 @@ test_expect_success 'create completely different structure' '
|/
* A
EOF
+
+ head="$(git show-ref --verify -s --abbrev HEAD)" &&
+ cat >expect <<-EOF &&
+ $head HEAD@{0}: rebase (finish): returning to refs/heads/main
+ $head HEAD@{1}: rebase (merge): Merge the topic branch ${SQ}onebranch${SQ}
+ EOF
+
+ git reflog -n2 HEAD >actual &&
+ test_cmp expect actual
'
test_expect_success 'generate correct todo list' '
--
gitgitgadget
