From 396da8f7a07ae02a6152e0c0fc3eaac8a99b4c65 Mon Sep 17 00:00:00 2001 From: Jeff King Date: Tue, 29 Dec 2015 00:57:25 -0500 Subject: create_symref: write reflog while holding lock We generally hold a lock on the matching ref while writing to its reflog; this prevents two simultaneous writers from clobbering each other's reflog lines (it does not even have to be two symref updates; because we don't hold the lock, we could race with somebody writing to the pointed-to ref via HEAD, for example). We can fix this by writing the reflog before we commit the lockfile. This runs the risk of writing the reflog but failing the final rename(), but at least we now err on the same side as the rest of the ref code. Noticed-by: Michael Haggerty Signed-off-by: Jeff King Reviewed-by: Michael Haggerty Signed-off-by: Junio C Hamano --- refs/files-backend.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'refs') diff --git a/refs/files-backend.c b/refs/files-backend.c index 3d1994debd..180c837d11 100644 --- a/refs/files-backend.c +++ b/refs/files-backend.c @@ -2850,12 +2850,13 @@ static int create_symref_locked(struct ref_lock *lock, const char *refname, return error("unable to fdopen %s: %s", lock->lk->tempfile.filename.buf, strerror(errno)); + update_symref_reflog(lock, refname, target, logmsg); + /* no error check; commit_ref will check ferror */ fprintf(lock->lk->tempfile.fp, "ref: %s\n", target); if (commit_ref(lock) < 0) return error("unable to write symref for %s: %s", refname, strerror(errno)); - update_symref_reflog(lock, refname, target, logmsg); return 0; } -- cgit v1.2.3