Be more careful about updating refs
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: 2016-06-15 22:44:05
Subsystem:
the rest · Maintainer:
Linus Torvalds
This makes write_ref_sha1() more careful: it actually checks the SHA1 of the ref it is updating, and refuses to update a ref with an object that it cannot find. Perhaps more importantly, it also refuses to update a branch head with a non-commit object. I don't quite know *how* the stable series maintainers were able to corrupt their repository to have a HEAD that pointed to a tag rather than a commit object, but they did. Which results in a totally broken repository that cannot be cloned or committed on. So make it harder for people to shoot themselves in the foot like that. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> --- I'm signing off on this, but I hope people will double-check this: I didn't actually test it very much. refs.c | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+), 0 deletions(-)
diff --git a/refs.c b/refs.c
index 58f6d17..c3ffe03 100644
--- a/refs.c
+++ b/refs.c@@ -1119,10 +1119,16 @@ static int log_ref_write(const char *ref_name, const unsigned char *old_sha1, return 0; } +static int is_branch(const char *refname) +{ + return !strcmp(refname, "HEAD") || !prefixcmp(refname, "refs/heads/"); +} + int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1, const char *logmsg) { static char term = '\n'; + struct object *o; if (!lock) return -1;
@@ -1130,6 +1136,19 @@ int write_ref_sha1(struct ref_lock *lock, unlock_ref(lock); return 0; } + o = parse_object(sha1); + if (!o) { + error("Trying to write ref %s with nonexistant object %s", + lock->ref_name, sha1_to_hex(sha1)); + unlock_ref(lock); + return -1; + } + if (o->type != OBJ_COMMIT && is_branch(lock->ref_name)) { + error("Trying to write non-commit object %s to branch %s", + sha1_to_hex(sha1), lock->ref_name); + unlock_ref(lock); + return -1; + } if (write_in_full(lock->lock_fd, sha1_to_hex(sha1), 40) != 40 || write_in_full(lock->lock_fd, &term, 1) != 1 || close(lock->lock_fd) < 0) {