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authorMichael Adam <obnox@samba.org>2012-04-11 15:51:40 +0200
committerAndreas Schneider <asn@samba.org>2012-04-25 14:31:11 +0200
commit22451f7f45c1f692dc9d40af0e6ce82666359390 (patch)
treef813a407c8869e3b9ce964e511dd641f9b0d71c2
parent7ea8bd3605adb3a53ca44ebdabfdcdb9c1aeaa18 (diff)
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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. Signed-off-by: Andreas Schneider <asn@samba.org>
-rw-r--r--source3/registry/reg_backend_db.c25
1 files changed, 22 insertions, 3 deletions
diff --git a/source3/registry/reg_backend_db.c b/source3/registry/reg_backend_db.c
index abe9f7bdca..ed7fe4d116 100644
--- a/source3/registry/reg_backend_db.c
+++ b/source3/registry/reg_backend_db.c
@@ -1712,6 +1712,7 @@ 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"));
@@ -1724,10 +1725,28 @@ 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, dbwrap_get_seqnum(db));
- W_ERROR_NOT_OK_GOTO_DONE(werr);
+ count = 0;
+ ZERO_STRUCT(value);
+ seqnum[0] = dbwrap_get_seqnum(db);
+
+ do {
+ count++;
+ TALLOC_FREE(value.dptr);
+ value = regdb_fetch_key_internal(db, frame, key);
+ seqnum[count % 2] = dbwrap_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",