Files
DanSandClaude Opus 5.5 7131b3673f qa: add fd-guard, the close() guard and regtest harness that found the double close
shim/ is an LD_PRELOAD guard around close/fclose/dup2/dup3:
- before each close it resolves /proc/self/fd/N;
- it reports, with a backtrace, a non-owner close of wallet.dat,
  database/log.* or blocks/*.dat, and every close that fails with EBADF
  (the second half of a double close);
- FDGUARD_ABORT=1 aborts on the first hit;
- run_tests.sh self-tests it (51 checks).

repro/ runs a shimmed dragonxd on isolated regtest. Each run gets its
own unprivileged network namespace (loopback only). The loads are:
- rpc: a hammer with impatient/RST/half-open clients, work-queue
  bursts and long-polls;
- p2p: TLS peers churned by disconnectnode, ban and kill, plus a raw
  TCP/TLS misbehaver;
- tor: a fake control port;
- mine: mining with blocknotify and autoshield.
tools/tally.py groups the reports by closer. tools/scan_bdb.py finds BDB
pages written into block files.

With the wolfSSL CloseSocket macro in effect:
- p2pmin (300 s) gives one EBADF double close per disconnect;
- the full load (1200 s) gives 930 EBADF closes, 186 non-owner closes
  (37 of wallet/log/blk files) and a 632 KB db.log with BDB0060 PANIC;
- RPC-only and Tor-only loads give none.
After the fix, every count is 0 and db.log stays empty. The README has
the commands and the numbers.

Paths come from the environment (GOLDEN, BIN, RUNS, SHIM, ASMAP and the
Sapling params). Run output goes to $RUNS, outside the tree.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-16 21:23:01 -05:00

114 lines
4.5 KiB
Python
Executable File

#!/usr/bin/env python3
"""
scan_bdb.py -- find Berkeley DB pages written into files that must not contain them
(blocks/blk*.dat, blocks/rev*.dat). Stand-in for the production incident tool.
BDB writes page P of a database at file offset P*pagesize through pwrite(fd, ...). If
fd has been closed and its number reused by a block file, the page lands in the block
file at exactly P*pagesize. So at every pagesize-aligned offset we decode the PAGE
header (db_page.h, all little-endian on x86):
0 u32 lsn.file 4 u32 lsn.offset 8 u32 pgno 12 u32 prev_pgno
16 u32 next_pgno 20 u16 entries 22 u16 hf_offset
24 u8 level 25 u8 type
and a metadata page (pgno 0 / any meta type) also carries magic at 12 and pagesize at 20.
A hit needs ALL of:
* pgno == offset // pagesize (the self-locating property)
* type is a real BDB page type (1..16 except 0)
* level consistent with type (overflow/meta/hash: 0; btree leaf: 1; internal: 2..32)
* hf_offset <= pagesize; entries <= pagesize/2
* for overflow (7): entries (refcount) >= 1 and 0 < hf_offset (data length) <= pagesize-26
Strength: "STRONG" if lsn == (0,1) (pages rewritten by lsn_reset -- the production
signature) or a meta page with a valid magic, else "weak".
Also reports any aligned BDB meta magic (btree 0x053162, hash 0x061561, queue 0x042253,
heap 0x074582) even when pgno does not match.
usage: scan_bdb.py [--pagesize 4096] [--all-offsets] files...
exit 0 = clean, 2 = hits.
"""
import argparse, struct, sys
TYPES = {1: "duplicate", 2: "hash_unsorted", 3: "ibtree", 4: "irecno", 5: "lbtree", 6: "lrecno",
7: "overflow", 8: "hashmeta", 9: "btreemeta", 10: "qammeta", 11: "qamdata", 12: "ldup",
13: "hash", 14: "heapmeta", 15: "heap", 16: "iheap"}
MAGIC = {0x053162: "btree", 0x061561: "hash", 0x042253: "queue", 0x074582: "heap"}
META = {8, 9, 10, 14}
def level_ok(t, lvl):
if t in (5, 6, 12): # leaf pages
return lvl == 1
if t in (3, 4): # internal pages
return 2 <= lvl <= 32
return lvl == 0 # overflow / meta / hash / queue / heap
def check(buf, off, ps):
if len(buf) < 26:
return None
lf, lo, pgno, prv, nxt, ent, hfo, lvl, typ = struct.unpack_from("<IIIIIHHBB", buf, 0)
if typ not in TYPES or pgno != off // ps or not level_ok(typ, lvl):
return None
if typ in META:
magic, ver, psz = struct.unpack_from("<III", buf, 12)
if magic not in MAGIC:
return None
return ("STRONG", f"{TYPES[typ]} magic={MAGIC[magic]} ver={ver} pagesize={psz} lsn=({lf},{lo})")
if hfo > ps or ent > ps // 2:
return None
if typ == 7 and not (ent >= 1 and 0 < hfo <= ps - 26):
return None
strength = "STRONG" if (lf, lo) == (0, 1) else "weak"
return (strength, f"{TYPES[typ]} lsn=({lf},{lo}) prev={prv} next={nxt} entries={ent} hf_offset={hfo} level={lvl}")
def scan(path, ps):
hits, magic_only = [], []
with open(path, "rb") as f:
off = 0
while True:
buf = f.read(ps)
if not buf:
break
r = check(buf, off, ps)
if r:
hits.append((off, off // ps) + r)
elif len(buf) >= 16:
m = struct.unpack_from("<I", buf, 12)[0]
if m in MAGIC and buf[25] in META:
magic_only.append((off, MAGIC[m]))
off += len(buf)
return hits, magic_only, off
def main():
ap = argparse.ArgumentParser()
ap.add_argument("--pagesize", type=int, default=4096)
ap.add_argument("--quiet", action="store_true")
ap.add_argument("files", nargs="+")
a = ap.parse_args()
total = strong = 0
for p in a.files:
try:
hits, mo, size = scan(p, a.pagesize)
except OSError as e:
print(f"{p}: ERROR {e}")
continue
s = sum(1 for h in hits if h[2] == "STRONG")
total += len(hits); strong += s
if hits or mo:
print(f"{p}: {len(hits)} BDB page(s) ({s} strong), {len(mo)} stray meta magic, size={size}")
if not a.quiet:
for h in hits[:20]:
print(f" off={h[0]} pgno={h[1]} {h[2]} {h[3]}")
for m in mo[:5]:
print(f" meta-magic off={m[0]} {m[1]}")
else:
print(f"{p}: clean ({size} bytes)")
print(f"TOTAL BDB pages found: {total} ({strong} strong)")
return 2 if total else 0
if __name__ == "__main__":
sys.exit(main())