From 521c7ea32d36263d218d98fc31420afc1b7cb0e1 Mon Sep 17 00:00:00 2001 From: Michael Adam Date: Wed, 11 Apr 2012 15:51:40 +0200 Subject: [PATCH] s3:registry: fix seqnum race in regdb_fetch_keys_internal This prevents race between fetching seqnum and key content. Because there is currently no way to atomically fetch the record along with the seqnum, I use a loop. This is far from optimal and should should ideally be done differently. But for now it fixes the race. (cherry picked from commit 66fcac5e479a530091ecb43d9f8cf90f4351ad17) --- source3/registry/reg_backend_db.c | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/source3/registry/reg_backend_db.c b/source3/registry/reg_backend_db.c index 995da66de66..68cd094588e 100644 --- a/source3/registry/reg_backend_db.c +++ b/source3/registry/reg_backend_db.c @@ -1615,6 +1615,7 @@ static WERROR regdb_fetch_keys_internal(struct db_context *db, const char *key, fstring subkeyname; TALLOC_CTX *frame = talloc_stackframe(); TDB_DATA value; + int seqnum[2], count; DEBUG(11,("regdb_fetch_keys: Enter key => [%s]\n", key ? key : "NULL")); @@ -1627,10 +1628,28 @@ static WERROR regdb_fetch_keys_internal(struct db_context *db, const char *key, werr = regsubkey_ctr_reinit(ctr); W_ERROR_NOT_OK_GOTO_DONE(werr); - werr = regsubkey_ctr_set_seqnum(ctr, db->get_seqnum(db)); - W_ERROR_NOT_OK_GOTO_DONE(werr); + count = 0; + ZERO_STRUCT(value); + seqnum[0] = db->get_seqnum(db); + + do { + count++; + TALLOC_FREE(value.dptr); + value = regdb_fetch_key_internal(db, frame, key); + seqnum[count % 2] = db->get_seqnum(db); - value = regdb_fetch_key_internal(db, frame, key); + } while (seqnum[0] != seqnum[1]); + + if (count > 1) { + DEBUG(5, ("regdb_fetch_keys_internal: it took %d attempts to " + "fetch key '%s' with constant seqnum\n", + count, key)); + } + + werr = regsubkey_ctr_set_seqnum(ctr, seqnum[0]); + if (!W_ERROR_IS_OK(werr)) { + goto done; + } if (value.dsize == 0 || value.dptr == NULL) { DEBUG(10, ("regdb_fetch_keys: no subkeys found for key [%s]\n", -- 2.34.1