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mdbx: fix rare SIGSEGV in cursor tracking code.

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The error was that the array of pointers in the transaction zeroed by the
value of env->me_numdbs and before txn->mt_numdbs was set to env->me_numdbs.
Thus, a cursor pointer(s) in the starting transaction could uninitialized if
another thread opened a dbi-handle(s) between the two aforementioned events.
This commit is contained in:
Леонид Юрьев (Leonid Yuriev) 2022-03-25 13:05:46 +03:00
parent d5e4c198d8
commit d522069080
1 changed files with 1 additions and 1 deletions
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2
src/core.c
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@ -7934,6 +7934,7 @@ static int mdbx_txn_renew0(MDBX_txn *txn, const unsigned flags) {
/* Setup db info */ /* Setup db info */
mdbx_compiler_barrier(); mdbx_compiler_barrier();
memset(txn->mt_cursors, 0, sizeof(MDBX_cursor *) * txn->mt_numdbs);
for (unsigned i = CORE_DBS; i < txn->mt_numdbs; i++) { for (unsigned i = CORE_DBS; i < txn->mt_numdbs; i++) {
const unsigned db_flags = env->me_dbflags[i]; const unsigned db_flags = env->me_dbflags[i];
txn->mt_dbs[i].md_flags = db_flags & DB_PERSISTENT_FLAGS; txn->mt_dbs[i].md_flags = db_flags & DB_PERSISTENT_FLAGS;
@ -8140,7 +8141,6 @@ int mdbx_txn_begin_ex(MDBX_env *env, MDBX_txn *parent, MDBX_txn_flags_t flags,
txn->mt_dbxs = env->me_dbxs; /* static */ txn->mt_dbxs = env->me_dbxs; /* static */
txn->mt_dbs = (MDBX_db *)((char *)txn + tsize); txn->mt_dbs = (MDBX_db *)((char *)txn + tsize);
txn->mt_cursors = (MDBX_cursor **)(txn->mt_dbs + env->me_maxdbs); txn->mt_cursors = (MDBX_cursor **)(txn->mt_dbs + env->me_maxdbs);
memset(txn->mt_cursors, 0, sizeof(MDBX_cursor *) * env->me_numdbs);
txn->mt_dbistate = (uint8_t *)txn + size - env->me_maxdbs; txn->mt_dbistate = (uint8_t *)txn + size - env->me_maxdbs;
txn->mt_flags = flags; txn->mt_flags = flags;
txn->mt_env = env; txn->mt_env = env;