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author | Volker Lendecke <vl@samba.org> | 2012-10-02 15:26:14 +0200 |
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committer | Volker Lendecke <vl@samba.org> | 2012-10-06 13:23:42 +0200 |
commit | c62f8baff878001ead921112dd653ff69d1cfe7d (patch) | |
tree | 4d9c706d56eba1f53d3a2a80e004619d06d5963f /lib/tdb/common/open.c | |
parent | 37fd93194db10fc832ed3fa1ec880ebc26be904b (diff) | |
download | samba-c62f8baff878001ead921112dd653ff69d1cfe7d.tar.gz samba-c62f8baff878001ead921112dd653ff69d1cfe7d.tar.bz2 samba-c62f8baff878001ead921112dd653ff69d1cfe7d.zip |
tdb: Make tdb robust against improper CLEAR_IF_FIRST restart
When winbind is restarted, there is a potential crash in tdb. Following
situation: We are in a cluster with ctdb. A winbind child hangs
in a request to the DC. Cluster monitoring decides the node has a
problem. Cluster monitoring decides to kill ctdbd. winbind child
still hangs in a RPC request. winbind parent figures that ctdb is
dead and immediately commits suicide. winbind parent is restarted by
cluster management, overwriting gencache.tdb with CLEAR_IF_FIRST. The
CLEAR_IF_FIRST logic as implemented now will not see that a child still
has the tdb open, only the parent holds the ACTIVE_LOCK due to performance
reasons. During the CLEAR_IF_FIRST logic is done, there is a very small
window where we ftruncate(tfd, 0) the file and re-write a proper header
without a lock. When during this small window the winbind child comes
back, wanting to store something into gencache.tdb, that winbind child
will crash with a SIGBUS.
Sounds unlikely? See:
[2012/09/29 07:02:31.871607, 0] lib/util.c:1183(smb_panic)
PANIC (pid 1814517): internal error
[2012/09/29 07:02:31.877596, 0] lib/util.c:1287(log_stack_trace)
BACKTRACE: 35 stack frames:
#0 winbindd(log_stack_trace+0x1a) [0x7feb7d4ca18a]
#1 winbindd(smb_panic+0x2b) [0x7feb7d4ca25b]
#2 winbindd(+0x1a3cc4) [0x7feb7d4bacc4]
#3 /lib64/libc.so.6(+0x32900) [0x7feb7a929900]
#4 /lib64/libc.so.6(memcpy+0x35) [0x7feb7a97f355]
#5 /usr/lib64/libtdb.so.1(+0x6e76) [0x7feb7b0b0e76]
#6 /usr/lib64/libtdb.so.1(+0x3d37) [0x7feb7b0add37]
#7 /usr/lib64/libtdb.so.1(+0x863d) [0x7feb7b0b263d]
#8 /usr/lib64/libtdb.so.1(+0x8700) [0x7feb7b0b2700]
#9 /usr/lib64/libtdb.so.1(+0x2505) [0x7feb7b0ac505]
#10 /usr/lib64/libtdb.so.1(+0x25b7) [0x7feb7b0ac5b7]
#11 /usr/lib64/libtdb.so.1(tdb_fetch+0x13) [0x7feb7b0ac633]
#12 winbindd(gencache_set_data_blob+0x259) [0x7feb7d4d8449]
#13 winbindd(gencache_set+0x53) [0x7feb7d4d85b3]
#14 winbindd(gencache_del+0x5e) [0x7feb7d4d879e]
#15 winbindd(saf_delete+0x93) [0x7feb7d54b693]
#16 winbindd(+0xe507e) [0x7feb7d3fc07e]
#17 winbindd(+0xe85e5) [0x7feb7d3ff5e5]
#18 winbindd(+0xe65be) [0x7feb7d3fd5be]
#19 winbindd(+0xe7562) [0x7feb7d3fe562]
#20 winbindd(init_dc_connection+0x2e) [0x7feb7d3fe5be]
#21 winbindd(+0xe75d9) [0x7feb7d3fe5d9]
#22 winbindd(cm_connect_netlogon+0x58) [0x7feb7d3fe658]
#23 winbindd(_wbint_PingDc+0x61) [0x7feb7d410991]
#24 winbindd(+0x103175) [0x7feb7d41a175]
#25 winbindd(winbindd_dual_ndrcmd+0xb7) [0x7feb7d4107d7]
#26 winbindd(+0xf8609) [0x7feb7d40f609]
#27 winbindd(+0xf9075) [0x7feb7d410075]
#28 winbindd(tevent_common_loop_immediate+0xe8) [0x7feb7d4db198]
#29 winbindd(run_events_poll+0x3c) [0x7feb7d4d93fc]
#30 winbindd(+0x1c2b52) [0x7feb7d4d9b52]
#31 winbindd(_tevent_loop_once+0x90) [0x7feb7d4d9f60]
#32 winbindd(main+0x7b3) [0x7feb7d3e7aa3]
#33 /lib64/libc.so.6(__libc_start_main+0xfd) [0x7feb7a915cdd]
#34 winbindd(+0xce2a9) [0x7feb7d3e52a9]
This is in a winbind child, logfiles surrounding indicate the parent
was restarted.
This patch takes all chain locks around the CLEAR_IF_FIRST introduced
tdb_new_database.
Diffstat (limited to 'lib/tdb/common/open.c')
-rw-r--r-- | lib/tdb/common/open.c | 32 |
1 files changed, 28 insertions, 4 deletions
diff --git a/lib/tdb/common/open.c b/lib/tdb/common/open.c index 8836f8442e..d9f76f0835 100644 --- a/lib/tdb/common/open.c +++ b/lib/tdb/common/open.c @@ -313,12 +313,36 @@ _PUBLIC_ struct tdb_context *tdb_open_ex(const char *name, int hash_size, int td if ((tdb_flags & TDB_CLEAR_IF_FIRST) && (!tdb->read_only) && (locked = (tdb_nest_lock(tdb, ACTIVE_LOCK, F_WRLCK, TDB_LOCK_NOWAIT|TDB_LOCK_PROBE) == 0))) { - open_flags |= O_CREAT; - if (ftruncate(tdb->fd, 0) == -1) { + int ret; + ret = tdb_brlock(tdb, F_WRLCK, FREELIST_TOP, 0, + TDB_LOCK_WAIT); + if (ret == -1) { TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: " - "failed to truncate %s: %s\n", + "tdb_brlock failed for %s: %s\n", name, strerror(errno))); - goto fail; /* errno set by ftruncate */ + goto fail; + } + ret = tdb_new_database(tdb, hash_size); + if (ret == -1) { + TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: " + "tdb_new_database failed for %s: %s\n", + name, strerror(errno))); + tdb_unlockall(tdb); + goto fail; + } + ret = tdb_brunlock(tdb, F_WRLCK, FREELIST_TOP, 0); + if (ret == -1) { + TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: " + "tdb_unlockall failed for %s: %s\n", + name, strerror(errno))); + goto fail; + } + ret = lseek(tdb->fd, 0, SEEK_SET); + if (ret == -1) { + TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_open_ex: " + "lseek failed for %s: %s\n", + name, strerror(errno))); + goto fail; } } |