From 11413a95a2db14ef14a8f8f4fcb1f11adf44e7a0 Mon Sep 17 00:00:00 2001 From: Michael Adam Date: Wed, 11 Apr 2012 15:48:02 +0200 Subject: [PATCH] s3:registry: fix seqnum race in fetch_values_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 13bccba3c2f6e6fdda2b4a40dd4b1e250a98a7ef) Conflicts: source3/registry/reg_backend_db.c --- source3/registry/reg_backend_db.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/source3/registry/reg_backend_db.c b/source3/registry/reg_backend_db.c index e0fe7c12115..c2c36dde141 100644 --- a/source3/registry/reg_backend_db.c +++ b/source3/registry/reg_backend_db.c @@ -1765,6 +1765,7 @@ static int regdb_fetch_values_internal(struct db_context *db, const char* key, int ret = 0; TDB_DATA value; WERROR werr; + int seqnum[2], count; DEBUG(10,("regdb_fetch_values: Looking for values of key [%s]\n", key)); @@ -1777,10 +1778,27 @@ static int regdb_fetch_values_internal(struct db_context *db, const char* key, goto done; } - werr = regval_ctr_set_seqnum(values, db->get_seqnum(db)); - W_ERROR_NOT_OK_GOTO_DONE(werr); + ZERO_STRUCT(value); + count = 0; + seqnum[0] = db->get_seqnum(db); + + do { + count++; + TALLOC_FREE(value.dptr); + value = regdb_fetch_key_internal(db, ctx, keystr); + seqnum[count % 2] = db->get_seqnum(db); + } while (seqnum[0] != seqnum[1]); + + if (count > 1) { + DEBUG(5, ("regdb_fetch_values_internal: it took %d attempts " + "to fetch key '%s' with constant seqnum\n", + count, key)); + } - value = regdb_fetch_key_internal(db, ctx, keystr); + werr = regval_ctr_set_seqnum(values, seqnum[0]); + if (!W_ERROR_IS_OK(werr)) { + goto done; + } if (!value.dptr) { /* all keys have zero values by default */ -- 2.34.1