[PATCH v4 4/6] Always check `parse_tree*()`'s return value

Johannes Schindelin via GitGitGadget
2024-02-23T08:34:32Z

From: Johannes Schindelin <johannes.schindelin@gmx.de>

Otherwise we may easily run into serious crashes: For example, if we run
`init_tree_desc()` directly after a failed `parse_tree()`, we are
accessing uninitialized data or trying to dereference `NULL`.

Note that the `parse_tree()` function already takes care of showing an
error message. The `parse_tree_indirectly()` and
`repo_get_commit_tree()` functions do not, therefore those latter call
sites need to show a useful error message while the former do not.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
builtin/checkout.c | 19 ++++++++++++++++---
builtin/clone.c | 3 ++-
builtin/commit.c | 3 ++-
builtin/merge-tree.c | 6 ++++++
builtin/read-tree.c | 3 ++-
builtin/reset.c | 4 ++++
cache-tree.c | 4 ++--
merge-ort.c | 3 +++
merge-recursive.c | 3 ++-
merge.c | 5 ++++-
reset.c | 5 +++++
sequencer.c | 4 ++++
12 files changed, 52 insertions(+), 10 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index f02434bc155..9ab0901d629 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -707,7 +707,8 @@ static int reset_tree(struct tree *tree, const struct checkout_opts *o,
init_checkout_metadata(&opts.meta, info->refname,
info->commit ? &info->commit->object.oid : null_oid(),
NULL);
- parse_tree(tree);
+ if (parse_tree(tree) < 0)
+ return 128;
init_tree_desc(&tree_desc, tree->buffer, tree->size);
switch (unpack_trees(1, &tree_desc, &opts)) {
case -2:
@@ -786,9 +787,15 @@ static int merge_working_tree(const struct checkout_opts *opts,
if (new_branch_info->commit)
BUG("'switch --orphan' should never accept a commit as starting point");
new_tree = parse_tree_indirect(the_hash_algo->empty_tree);
- } else
+ if (!new_tree)
+ BUG("unable to read empty tree");
+ } else {
new_tree = repo_get_commit_tree(the_repository,
new_branch_info->commit);
+ if (!new_tree)
+ return error(_("unable to read tree (%s)"),
+ oid_to_hex(&new_branch_info->commit->object.oid));
+ }
if (opts->discard_changes) {
ret = reset_tree(new_tree, opts, 1, writeout_error, new_branch_info);
if (ret)
@@ -823,7 +830,8 @@ static int merge_working_tree(const struct checkout_opts *opts,
oid_to_hex(old_commit_oid));

init_tree_desc(&trees[0], tree->buffer, tree->size);
- parse_tree(new_tree);
+ if (parse_tree(new_tree) < 0)
+ exit(128);
tree = new_tree;
init_tree_desc(&trees[1], tree->buffer, tree->size);

@@ -1239,10 +1247,15 @@ static void setup_new_branch_info_and_source_tree(
if (!new_branch_info->commit) {
/* not a commit */
*source_tree = parse_tree_indirect(rev);
+ if (!*source_tree)
+ die(_("unable to read tree (%s)"), oid_to_hex(rev));
} else {
parse_commit_or_die(new_branch_info->commit);
*source_tree = repo_get_commit_tree(the_repository,
new_branch_info->commit);
+ if (!*source_tree)
+ die(_("unable to read tree (%s)"),
+ oid_to_hex(&new_branch_info->commit->object.oid));
}
}

diff --git a/builtin/clone.c b/builtin/clone.c
index c6357af9498..4410b55be98 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -736,7 +736,8 @@ static int checkout(int submodule_progress, int filter_submodules)
tree = parse_tree_indirect(&oid);
if (!tree)
die(_("unable to parse commit %s"), oid_to_hex(&oid));
- parse_tree(tree);
+ if (parse_tree(tree) < 0)
+ exit(128);
init_tree_desc(&t, tree->buffer, tree->size);
if (unpack_trees(1, &t, &opts) < 0)
die(_("unable to checkout working tree"));
diff --git a/builtin/commit.c b/builtin/commit.c
index 781af2e206c..0723f06de7a 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -339,7 +339,8 @@ static void create_base_index(const struct commit *current_head)
tree = parse_tree_indirect(&current_head->object.oid);
if (!tree)
die(_("failed to unpack HEAD tree object"));
- parse_tree(tree);
+ if (parse_tree(tree) < 0)
+ exit(128);
init_tree_desc(&t, tree->buffer, tree->size);
if (unpack_trees(1, &t, &opts))
exit(128); /* We've already reported the error, finish dying */
diff --git a/builtin/merge-tree.c b/builtin/merge-tree.c
index 2d4ce5b3886..3492a575a6c 100644
--- a/builtin/merge-tree.c
+++ b/builtin/merge-tree.c
@@ -447,12 +447,18 @@ static int real_merge(struct merge_tree_options *o,
if (repo_get_oid_treeish(the_repository, merge_base, &base_oid))
die(_("could not parse as tree '%s'"), merge_base);
base_tree = parse_tree_indirect(&base_oid);
+ if (!base_tree)
+ die(_("unable to read tree (%s)"), oid_to_hex(&base_oid));
if (repo_get_oid_treeish(the_repository, branch1, &head_oid))
die(_("could not parse as tree '%s'"), branch1);
parent1_tree = parse_tree_indirect(&head_oid);
+ if (!parent1_tree)
+ die(_("unable to read tree (%s)"), oid_to_hex(&head_oid));
if (repo_get_oid_treeish(the_repository, branch2, &merge_oid))
die(_("could not parse as tree '%s'"), branch2);
parent2_tree = parse_tree_indirect(&merge_oid);
+ if (!parent2_tree)
+ die(_("unable to read tree (%s)"), oid_to_hex(&merge_oid));

opt.ancestor = merge_base;
merge_incore_nonrecursive(&opt, base_tree, parent1_tree, parent2_tree, &result);
diff --git a/builtin/read-tree.c b/builtin/read-tree.c
index 8196ca9dd85..5923ed36893 100644
--- a/builtin/read-tree.c
+++ b/builtin/read-tree.c
@@ -263,7 +263,8 @@ int cmd_read_tree(int argc, const char **argv, const char *cmd_prefix)
cache_tree_free(&the_index.cache_tree);
for (i = 0; i < nr_trees; i++) {
struct tree *tree = trees[i];
- parse_tree(tree);
+ if (parse_tree(tree) < 0)
+ return 128;
init_tree_desc(t+i, tree->buffer, tree->size);
}
if (unpack_trees(nr_trees, t, &opts))
diff --git a/builtin/reset.c b/builtin/reset.c
index 4b018d20e3b..fd36fc5bd95 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -119,6 +119,10 @@ static int reset_index(const char *ref, const struct object_id *oid, int reset_t

if (reset_type == MIXED || reset_type == HARD) {
tree = parse_tree_indirect(oid);
+ if (!tree) {
+ error(_("unable to read tree (%s)"), oid_to_hex(oid));
+ goto out;
+ }
prime_cache_tree(the_repository, the_repository->index, tree);
}

diff --git a/cache-tree.c b/cache-tree.c
index 641427ed410..c6508b64a5c 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -779,8 +779,8 @@ static void prime_cache_tree_rec(struct repository *r,
struct cache_tree_sub *sub;
struct tree *subtree = lookup_tree(r, &entry.oid);

- if (!subtree->object.parsed)
- parse_tree(subtree);
+ if (!subtree->object.parsed && parse_tree(subtree) < 0)
+ exit(128);
sub = cache_tree_sub(it, entry.path);
sub->cache_tree = cache_tree();

diff --git a/merge-ort.c b/merge-ort.c
index 79d9e18f63d..910ba38ff05 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -4983,6 +4983,9 @@ static void merge_ort_nonrecursive_internal(struct merge_options *opt,

if (result->clean >= 0) {
result->tree = parse_tree_indirect(&working_tree_oid);
+ if (!result->tree)
+ die(_("unable to read tree (%s)"),
+ oid_to_hex(&working_tree_oid));
/* existence of conflicted entries implies unclean */
result->clean &= strmap_empty(&opt->priv->conflicted);
}
diff --git a/merge-recursive.c b/merge-recursive.c
index e3beb0801b1..10d41bfd487 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -410,7 +410,8 @@ static inline int merge_detect_rename(struct merge_options *opt)

static void init_tree_desc_from_tree(struct tree_desc *desc, struct tree *tree)
{
- parse_tree(tree);
+ if (parse_tree(tree) < 0)
+ exit(128);
init_tree_desc(desc, tree->buffer, tree->size);
}

diff --git a/merge.c b/merge.c
index b60925459c2..14a7325859d 100644
--- a/merge.c
+++ b/merge.c
@@ -80,7 +80,10 @@ int checkout_fast_forward(struct repository *r,
return -1;
}
for (i = 0; i < nr_trees; i++) {
- parse_tree(trees[i]);
+ if (parse_tree(trees[i]) < 0) {
+ rollback_lock_file(&lock_file);
+ return -1;
+ }
init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
}

diff --git a/reset.c b/reset.c
index 48da0adf851..080bcb6d656 100644
--- a/reset.c
+++ b/reset.c
@@ -158,6 +158,11 @@ int reset_head(struct repository *r, const struct reset_head_opts *opts)
}

tree = parse_tree_indirect(oid);
+ if (!tree) {
+ ret = error(_("unable to read tree (%s)"), oid_to_hex(oid));
+ goto leave_reset_head;
+ }
+
prime_cache_tree(r, r->index, tree);

if (write_locked_index(r->index, &lock, COMMIT_LOCK) < 0) {
diff --git a/sequencer.c b/sequencer.c
index d584cac8ed9..33d12b2ffd1 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -715,6 +715,8 @@ static int do_recursive_merge(struct repository *r,
o.show_rename_progress = 1;

head_tree = parse_tree_indirect(head);
+ if (!head_tree)
+ return error(_("unable to read tree (%s)"), oid_to_hex(head));
next_tree = next ? repo_get_commit_tree(r, next) : empty_tree(r);
base_tree = base ? repo_get_commit_tree(r, base) : empty_tree(r);

@@ -3887,6 +3889,8 @@ static int do_reset(struct repository *r,
}

tree = parse_tree_indirect(&oid);
+ if (!tree)
+ return error(_("unable to read tree (%s)"), oid_to_hex(&oid));
prime_cache_tree(r, r->index, tree);

if (write_locked_index(r->index, &lock, COMMIT_LOCK) < 0)