From 022b4d4aa6861c1e3e6d76484d92555221cb6d14 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Thu, 22 Oct 2009 00:10:34 +1030 Subject: lib/tdb: add tdb_check() ctdb wants a quick way to detect corrupt tdbs; particularly, tdbs with loops in their hash chains. tdb_check() provides this. Signed-off-by: Rusty Russell --- lib/tdb/common/check.c | 422 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 422 insertions(+) create mode 100644 lib/tdb/common/check.c (limited to 'lib/tdb/common') diff --git a/lib/tdb/common/check.c b/lib/tdb/common/check.c new file mode 100644 index 0000000000..94240bbed1 --- /dev/null +++ b/lib/tdb/common/check.c @@ -0,0 +1,422 @@ + /* + Unix SMB/CIFS implementation. + + trivial database library + + Copyright (C) Rusty Russell 2009 + + ** NOTE! The following LGPL license applies to the tdb + ** library. This does NOT imply that all of Samba is released + ** under the LGPL + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 3 of the License, or (at your option) any later version. + + This library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with this library; if not, see . +*/ +#include "tdb_private.h" + +/* Since we opened it, these shouldn't fail unless it's recent corruption. */ +static bool tdb_check_header(struct tdb_context *tdb, tdb_off_t *recovery) +{ + struct tdb_header hdr; + + if (tdb->methods->tdb_read(tdb, 0, &hdr, sizeof(hdr), DOCONV()) == -1) + return false; + if (strcmp(hdr.magic_food, TDB_MAGIC_FOOD) != 0) + goto corrupt; + + CONVERT(hdr); + if (hdr.version != TDB_VERSION) + goto corrupt; + + if (hdr.rwlocks != 0) + goto corrupt; + + if (hdr.hash_size == 0) + goto corrupt; + + if (hdr.hash_size != tdb->header.hash_size) + goto corrupt; + + if (hdr.recovery_start != 0 && + hdr.recovery_start < TDB_DATA_START(tdb->header.hash_size)) + goto corrupt; + + *recovery = hdr.recovery_start; + return true; + +corrupt: + tdb->ecode = TDB_ERR_CORRUPT; + TDB_LOG((tdb, TDB_DEBUG_ERROR, "Header is corrupt\n")); + return false; +} + +/* Generic record header check. */ +static bool tdb_check_record(struct tdb_context *tdb, + tdb_off_t off, + const struct list_struct *rec) +{ + tdb_off_t tailer; + + /* Check rec->next: 0 or points to record offset, aligned. */ + if (rec->next > 0 && rec->next < TDB_DATA_START(tdb->header.hash_size)){ + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Record offset %d too small next %d\n", + off, rec->next)); + goto corrupt; + } + if (rec->next + sizeof(*rec) < rec->next) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Record offset %d too large next %d\n", + off, rec->next)); + goto corrupt; + } + if ((rec->next % TDB_ALIGNMENT) != 0) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Record offset %d misaligned next %d\n", + off, rec->next)); + goto corrupt; + } + if (tdb->methods->tdb_oob(tdb, rec->next+sizeof(*rec), 0)) + goto corrupt; + + /* Check rec_len: similar to rec->next, implies next record. */ + if ((rec->rec_len % TDB_ALIGNMENT) != 0) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Record offset %d misaligned length %d\n", + off, rec->rec_len)); + goto corrupt; + } + /* Must fit tailer. */ + if (rec->rec_len < sizeof(tailer)) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Record offset %d too short length %d\n", + off, rec->rec_len)); + goto corrupt; + } + /* OOB allows "right at the end" access, so this works for last rec. */ + if (tdb->methods->tdb_oob(tdb, off+sizeof(*rec)+rec->rec_len, 0)) + goto corrupt; + + /* Check tailer. */ + if (tdb_ofs_read(tdb, off+sizeof(*rec)+rec->rec_len-sizeof(tailer), + &tailer) == -1) + goto corrupt; + if (tailer != sizeof(*rec) + rec->rec_len) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Record offset %d invalid tailer\n", off)); + goto corrupt; + } + + return true; + +corrupt: + tdb->ecode = TDB_ERR_CORRUPT; + return false; +} + +/* Grab some bytes: may copy if can't use mmap. + Caller has already done bounds check. */ +static TDB_DATA get_bytes(struct tdb_context *tdb, + tdb_off_t off, tdb_len_t len) +{ + TDB_DATA d; + + d.dsize = len; + + if (tdb->transaction == NULL && tdb->map_ptr != NULL) + d.dptr = (unsigned char *)tdb->map_ptr + off; + else + d.dptr = tdb_alloc_read(tdb, off, d.dsize); + return d; +} + +/* Frees data if we're not able to simply use mmap. */ +static void put_bytes(struct tdb_context *tdb, TDB_DATA d) +{ + if (tdb->transaction == NULL && tdb->map_ptr != NULL) + return; + free(d.dptr); +} + +/* We use the excellent Jenkins lookup3 hash; this is based on hash_word2. + * See: http://burtleburtle.net/bob/c/lookup3.c + */ +#define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k)))) +static void hash(uint32_t key, uint32_t *pc, uint32_t *pb) +{ + uint32_t a,b,c; + + /* Set up the internal state */ + a = b = c = 0xdeadbeef + *pc; + c += *pb; + a += key; + c ^= b; c -= rot(b,14); + a ^= c; a -= rot(c,11); + b ^= a; b -= rot(a,25); + c ^= b; c -= rot(b,16); + a ^= c; a -= rot(c,4); + b ^= a; b -= rot(a,14); + c ^= b; c -= rot(b,24); + *pc=c; *pb=b; +} + +/* + We want to check that all free records are in the free list + (only once), and all free list entries are free records. Similarly + for each hash chain of used records. + + Doing that naively (without walking hash chains, since we want to be + linear) means keeping a list of records which have been seen in each + hash chain, and another of records pointed to (ie. next pointers + from records and the initial hash chain heads). These two lists + should be equal. This will take 8 bytes per record, and require + sorting at the end. + + So instead, we record each offset in a bitmap such a way that + recording it twice will cancel out. Since each offset should appear + exactly twice, the bitmap should be zero at the end. + + The approach was inspired by Bloom Filters (see Wikipedia). For + each value, we flip K bits in a bitmap of size N. The number of + distinct arrangements is: + + N! / (K! * (N-K)!) + + Of course, not all arrangements are actually distinct, but testing + shows this formula to be close enough. + + So, if K == 8 and N == 256, the probability of two things flipping the same + bits is 1 in 409,663,695,276,000. + + Given that ldb uses a hash size of 10000, using 32 bytes per hash chain + (320k) seems reasonable. +*/ +#define NUM_HASHES 8 +#define BITMAP_BITS 256 + +static void bit_flip(unsigned char bits[], unsigned int idx) +{ + bits[idx / CHAR_BIT] ^= (1 << (idx % CHAR_BIT)); +} + +/* We record offsets in a bitmap for the particular chain it should be in. */ +static void record_offset(unsigned char bits[], tdb_off_t off) +{ + uint32_t h1 = off, h2 = 0; + unsigned int i; + + /* We get two good hash values out of jhash2, so we use both. Then + * we keep going to produce further hash values. */ + for (i = 0; i < NUM_HASHES / 2; i++) { + hash(off, &h1, &h2); + bit_flip(bits, h1 % BITMAP_BITS); + bit_flip(bits, h2 % BITMAP_BITS); + h2++; + } +} + +/* Check that an in-use record is valid. */ +static bool tdb_check_used_record(struct tdb_context *tdb, + tdb_off_t off, + const struct list_struct *rec, + unsigned char **hashes, + int (*check)(TDB_DATA, TDB_DATA, void *), + void *private_data) +{ + TDB_DATA key, data; + + if (!tdb_check_record(tdb, off, rec)) + return false; + + /* key + data + tailer must fit in record */ + if (rec->key_len + rec->data_len + sizeof(tdb_off_t) > rec->rec_len) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Record offset %d too short for contents\n", off)); + return false; + } + + key = get_bytes(tdb, off + sizeof(*rec), rec->key_len); + if (!key.dptr) + return false; + + if (tdb->hash_fn(&key) != rec->full_hash) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Record offset %d has incorrect hash\n", off)); + goto fail_put_key; + } + + /* Mark this offset as a known value for this hash bucket. */ + record_offset(hashes[BUCKET(rec->full_hash)+1], off); + /* And similarly if the next pointer is valid. */ + if (rec->next) + record_offset(hashes[BUCKET(rec->full_hash)+1], rec->next); + + /* If they supply a check function and this record isn't dead, + get data and feed it. */ + if (check && rec->magic != TDB_DEAD_MAGIC) { + data = get_bytes(tdb, off + sizeof(*rec) + rec->key_len, + rec->data_len); + if (!data.dptr) + goto fail_put_key; + + if (check(key, data, private_data) == -1) + goto fail_put_data; + put_bytes(tdb, data); + } + + put_bytes(tdb, key); + return true; + +fail_put_data: + put_bytes(tdb, data); +fail_put_key: + put_bytes(tdb, key); + return false; +} + +/* Check that an unused record is valid. */ +static bool tdb_check_free_record(struct tdb_context *tdb, + tdb_off_t off, + const struct list_struct *rec, + unsigned char **hashes) +{ + if (!tdb_check_record(tdb, off, rec)) + return false; + + /* Mark this offset as a known value for the free list. */ + record_offset(hashes[0], off); + /* And similarly if the next pointer is valid. */ + if (rec->next) + record_offset(hashes[0], rec->next); + return true; +} + +int tdb_check(struct tdb_context *tdb, + int (*check)(TDB_DATA key, TDB_DATA data, void *private_data), + void *private_data) +{ + unsigned int h; + unsigned char **hashes; + tdb_off_t off, recovery_start; + struct list_struct rec; + bool found_recovery = false; + + if (tdb_lockall(tdb) == -1) + return -1; + + /* Make sure we know true size of the underlying file. */ + tdb->methods->tdb_oob(tdb, tdb->map_size + 1, 1); + + /* Header must be OK: also gets us the recovery ptr, if any. */ + if (!tdb_check_header(tdb, &recovery_start)) + goto unlock; + + /* We should have the whole header, too. */ + if (tdb->map_size < TDB_DATA_START(tdb->header.hash_size)) { + tdb->ecode = TDB_ERR_CORRUPT; + TDB_LOG((tdb, TDB_DEBUG_ERROR, "File too short for hashes\n")); + goto unlock; + } + + /* One big malloc: pointers then bit arrays. */ + hashes = calloc(1, sizeof(hashes[0]) * (1+tdb->header.hash_size) + + BITMAP_BITS / CHAR_BIT * (1+tdb->header.hash_size)); + if (!hashes) { + tdb->ecode = TDB_ERR_OOM; + goto unlock; + } + + /* Initialize pointers */ + hashes[0] = (unsigned char *)(&hashes[1+tdb->header.hash_size]); + for (h = 1; h < 1+tdb->header.hash_size; h++) + hashes[h] = hashes[h-1] + BITMAP_BITS / CHAR_BIT; + + /* Freelist and hash headers are all in a row: read them. */ + for (h = 0; h < 1+tdb->header.hash_size; h++) { + if (tdb_ofs_read(tdb, FREELIST_TOP + h*sizeof(tdb_off_t), + &off) == -1) + goto free; + if (off) + record_offset(hashes[h], off); + } + + /* For each record, read it in and check it's ok. */ + for (off = TDB_DATA_START(tdb->header.hash_size); + off < tdb->map_size; + off += sizeof(rec) + rec.rec_len) { + if (tdb->methods->tdb_read(tdb, off, &rec, sizeof(rec), + DOCONV()) == -1) + goto free; + switch (rec.magic) { + case TDB_MAGIC: + case TDB_DEAD_MAGIC: + if (!tdb_check_used_record(tdb, off, &rec, hashes, + check, private_data)) + goto free; + break; + case TDB_FREE_MAGIC: + if (!tdb_check_free_record(tdb, off, &rec, hashes)) + goto free; + break; + case TDB_RECOVERY_MAGIC: + case 0: /* Used for invalid (or in-progress) recovery area. */ + if (recovery_start != off) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Unexpected recovery record at offset %d\n", + off)); + goto free; + } + found_recovery = true; + break; + default: + tdb->ecode = TDB_ERR_CORRUPT; + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Bad magic 0x%x at offset %d\n", + rec.magic, off)); + goto free; + } + } + + /* Now, hashes should all be empty: each record exists and is referred + * to by one other. */ + for (h = 0; h < 1+tdb->header.hash_size; h++) { + unsigned int i; + for (i = 0; i < BITMAP_BITS / CHAR_BIT; i++) { + if (hashes[h][i] != 0) { + tdb->ecode = TDB_ERR_CORRUPT; + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Hashes do not match records\n")); + goto free; + } + } + } + + /* We must have found recovery area if there was one. */ + if (recovery_start != 0 && !found_recovery) { + TDB_LOG((tdb, TDB_DEBUG_ERROR, + "Expected %s recovery area, got %s\n", + recovery_start ? "a" : "no", + found_recovery ? "one" : "none")); + goto free; + } + + free(hashes); + tdb_unlockall(tdb); + return 0; + +free: + free(hashes); +unlock: + tdb_unlockall(tdb); + return -1; +} -- cgit