In t4058 we have some tests that exercise git-read-tree(1) when used
with a tree that contains duplicate entries. While the expectation is
that we fail, we ideally should fail gracefully without a segfault.
But that is not the case: we never check that the number of entries in
the cache-tree is less than or equal to the number of entries in the
index. This can lead to an out-of-bounds read as we unconditionally
access `istate->cache[idx]`, where `idx` is controlled by the number of
cache-tree entries and the current position therein. The result is a
segfault.
Fix this segfault by adding a sanity check for the number of index
entries before dereferencing them.
Signed-off-by: Patrick Steinhardt <ps@xxxxxx>
---
cache-tree.c | 5 +++++
t/t4058-diff-duplicates.sh | 12 ++++++------
2 files changed, 11 insertions(+), 6 deletions(-)
diff --git a/cache-tree.c b/cache-tree.c
index 4228b6fad4..1e62567308 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -933,6 +933,11 @@ static int verify_one(struct repository *r,
pos = 0;
}
+ if (it->entry_count + pos > istate->cache_nr) {
+ ret = error(_("corrupted cache-tree has entries not present in index"));
+ goto out;
+ }
+
i = 0;
while (i < it->entry_count) {
struct cache_entry *ce = istate->cache[pos + i];
diff --git a/t/t4058-diff-duplicates.sh b/t/t4058-diff-duplicates.sh
index 2501c89c1c..3f602adb05 100755
--- a/t/t4058-diff-duplicates.sh
+++ b/t/t4058-diff-duplicates.sh
@@ -132,15 +132,15 @@ test_expect_success 'create a few commits' '
rm commit_id up final
'
-test_expect_failure 'git read-tree does not segfault' '
- test_when_finished rm .git/index.lock &&
- test_might_fail git read-tree --reset base
+test_expect_success 'git read-tree does not segfault' '
+ test_must_fail git read-tree --reset base 2>err &&
+ test_grep "error: corrupted cache-tree has entries not present in index" err
'
-test_expect_failure 'reset --hard does not segfault' '
- test_when_finished rm .git/index.lock &&
+test_expect_success 'reset --hard does not segfault' '
git checkout base &&
- test_might_fail git reset --hard
+ test_must_fail git reset --hard 2>err &&
+ test_grep "error: corrupted cache-tree has entries not present in index" err
'
test_expect_failure 'git diff HEAD does not segfault' '
--
2.47.0.rc0.dirty
