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Use global mutex instead file lock to fix issues with threaded mpm's #1224

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dc69c72
Use global mutex instead sdbm file lock to fix issues with threaded m…
Sep 28, 2016
deaa65a
Move locking before table update
Nov 4, 2016
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22 changes: 22 additions & 0 deletions apache2/modsecurity.c
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Original file line number Diff line number Diff line change
Expand Up @@ -169,6 +169,22 @@ int modsecurity_init(msc_engine *msce, apr_pool_t *mp) {
return -1;
}
#endif /* SET_MUTEX_PERMS */

rc = apr_global_mutex_create(&msce->dbm_lock, NULL, APR_LOCK_DEFAULT, mp);
if (rc != APR_SUCCESS) {
return -1;
}

#ifdef __SET_MUTEX_PERMS
#if AP_SERVER_MAJORVERSION_NUMBER > 1 && AP_SERVER_MINORVERSION_NUMBER > 2
rc = ap_unixd_set_global_mutex_perms(msce->dbm_lock);
#else
rc = unixd_set_global_mutex_perms(msce->dbm_lock);
#endif
if (rc != APR_SUCCESS) {
return -1;
}
#endif /* SET_MUTEX_PERMS */
#endif

return 1;
Expand All @@ -195,6 +211,12 @@ void modsecurity_child_init(msc_engine *msce) {
}
}

if (msce->dbm_lock != NULL) {
apr_status_t rc = apr_global_mutex_child_init(&msce->dbm_lock, NULL, msce->mp);
if (rc != APR_SUCCESS) {
// ap_log_error(APLOG_MARK, APLOG_ERR, rs, s, "Failed to child-init dbm mutex");
}
}
}

/**
Expand Down
1 change: 1 addition & 0 deletions apache2/modsecurity.h
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Original file line number Diff line number Diff line change
Expand Up @@ -657,6 +657,7 @@ struct msc_engine {
apr_pool_t *mp;
apr_global_mutex_t *auditlog_lock;
apr_global_mutex_t *geo_lock;
apr_global_mutex_t *dbm_lock;
msre_engine *msre;
unsigned int processing_mode;
};
Expand Down
68 changes: 46 additions & 22 deletions apache2/persist_dbm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,7 @@ static apr_table_t *collection_retrieve_ex(apr_sdbm_t *existing_dbm, modsec_rec
int expired = 0;
int i;


if (msr->txcfg->data_dir == NULL) {
msr_log(msr, 1, "collection_retrieve_ex: Unable to retrieve collection (name \"%s\", key \"%s\"). Use "
"SecDataDir to define data directory first.", log_escape(msr->mp, col_name),
Expand All @@ -119,10 +120,18 @@ static apr_table_t *collection_retrieve_ex(apr_sdbm_t *existing_dbm, modsec_rec
key.dsize = col_key_len + 1;

if (existing_dbm == NULL) {
rc = apr_global_mutex_lock(msr->modsecurity->dbm_lock);
if (rc != APR_SUCCESS) {
msr_log(msr, 1, "collection_retrieve_ex: Failed to lock proc mutex: %s",
get_apr_error(msr->mp, rc));
goto cleanup;
}

rc = apr_sdbm_open(&dbm, dbm_filename, APR_READ | APR_SHARELOCK,
CREATEMODE, msr->mp);
if (rc != APR_SUCCESS) {
dbm = NULL;
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
goto cleanup;
}
}
Expand Down Expand Up @@ -156,6 +165,7 @@ static apr_table_t *collection_retrieve_ex(apr_sdbm_t *existing_dbm, modsec_rec
/* Close after "value" used from fetch or memory may be overwritten. */
if (existing_dbm == NULL) {
apr_sdbm_close(dbm);
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
dbm = NULL;
}

Expand Down Expand Up @@ -202,12 +212,19 @@ static apr_table_t *collection_retrieve_ex(apr_sdbm_t *existing_dbm, modsec_rec
*/
if (apr_table_get(col, "KEY") == NULL) {
if (existing_dbm == NULL) {
rc = apr_global_mutex_lock(msr->modsecurity->dbm_lock);
if (rc != APR_SUCCESS) {
msr_log(msr, 1, "collection_retrieve_ex: Failed to lock proc mutex: %s",
get_apr_error(msr->mp, rc));
goto cleanup;
}
rc = apr_sdbm_open(&dbm, dbm_filename, APR_CREATE | APR_WRITE | APR_SHARELOCK,
CREATEMODE, msr->mp);
if (rc != APR_SUCCESS) {
msr_log(msr, 1, "collection_retrieve_ex: Failed to access DBM file \"%s\": %s",
log_escape(msr->mp, dbm_filename), get_apr_error(msr->mp, rc));
dbm = NULL;
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
goto cleanup;
}
}
Expand All @@ -227,6 +244,7 @@ static apr_table_t *collection_retrieve_ex(apr_sdbm_t *existing_dbm, modsec_rec

if (existing_dbm == NULL) {
apr_sdbm_close(dbm);
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
dbm = NULL;
}

Expand Down Expand Up @@ -289,14 +307,16 @@ static apr_table_t *collection_retrieve_ex(apr_sdbm_t *existing_dbm, modsec_rec
log_escape(msr->mp, col_name), log_escape_ex(msr->mp, col_key, col_key_len));

apr_sdbm_close(dbm);
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
}

return col;

cleanup:

if ((existing_dbm == NULL) && dbm) {
apr_sdbm_close(dbm);
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
}

return NULL;
Expand Down Expand Up @@ -361,6 +381,14 @@ int collection_store(modsec_rec *msr, apr_table_t *col) {
log_escape(msr->mp, dbm_filename));
}

/* Need to lock to pull in the stored data again and apply deltas. */
rc = apr_global_mutex_lock(msr->modsecurity->dbm_lock);
if (rc != APR_SUCCESS) {
msr_log(msr, 1, "collection_store: Failed to lock proc mutex: %s",
get_apr_error(msr->mp, rc));
goto error;
}

/* Delete IS_NEW on store. */
apr_table_unset(col, "IS_NEW");

Expand Down Expand Up @@ -408,7 +436,7 @@ int collection_store(modsec_rec *msr, apr_table_t *col) {
var->value = apr_psprintf(msr->mp, "%d", counter + 1);
var->value_len = strlen(var->value);
}

/* ENH Make the expiration timestamp accessible in blob form so that
* it is easier/faster to determine expiration without having to
* convert back to table form
Expand All @@ -417,19 +445,13 @@ int collection_store(modsec_rec *msr, apr_table_t *col) {
rc = apr_sdbm_open(&dbm, dbm_filename, APR_CREATE | APR_WRITE | APR_SHARELOCK,
CREATEMODE, msr->mp);
if (rc != APR_SUCCESS) {
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
msr_log(msr, 1, "collection_store: Failed to access DBM file \"%s\": %s", log_escape(msr->mp, dbm_filename),
get_apr_error(msr->mp, rc));
dbm = NULL;
goto error;
}

/* Need to lock to pull in the stored data again and apply deltas. */
rc = apr_sdbm_lock(dbm, APR_FLOCK_EXCLUSIVE);
if (rc != APR_SUCCESS) {
msr_log(msr, 1, "collection_store: Failed to exclusivly lock DBM file \"%s\": %s", log_escape(msr->mp, dbm_filename),
get_apr_error(msr->mp, rc));
goto error;
}


/* If there is an original value, then create a delta and
* apply the delta to the current value */
Expand Down Expand Up @@ -492,8 +514,8 @@ int collection_store(modsec_rec *msr, apr_table_t *col) {
blob = apr_pcalloc(msr->mp, blob_size);
if (blob == NULL) {
if (dbm != NULL) {
apr_sdbm_unlock(dbm);
apr_sdbm_close(dbm);
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
}

return -1;
Expand Down Expand Up @@ -550,16 +572,16 @@ int collection_store(modsec_rec *msr, apr_table_t *col) {
msr_log(msr, 1, "collection_store: Failed to write to DBM file \"%s\": %s", dbm_filename,
get_apr_error(msr->mp, rc));
if (dbm != NULL) {
apr_sdbm_unlock(dbm);
apr_sdbm_close(dbm);
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
}

return -1;
}

apr_sdbm_unlock(dbm);
apr_sdbm_close(dbm);

apr_global_mutex_unlock(msr->modsecurity->dbm_lock);

if (msr->txcfg->debuglog_level >= 4) {
msr_log(msr, 4, "collection_store: Persisted collection (name \"%s\", key \"%s\").",
log_escape_ex(msr->mp, var_name->value, var_name->value_len),
Expand Down Expand Up @@ -603,9 +625,17 @@ int collections_remove_stale(modsec_rec *msr, const char *col_name) {
log_escape(msr->mp, dbm_filename));
}

rc = apr_global_mutex_lock(msr->modsecurity->dbm_lock);
if (rc != APR_SUCCESS) {
msr_log(msr, 1, "collections_remove_stale: Failed to lock proc mutex: %s",
get_apr_error(msr->mp, rc));
goto error;
}

rc = apr_sdbm_open(&dbm, dbm_filename, APR_CREATE | APR_WRITE | APR_SHARELOCK,
CREATEMODE, msr->mp);
if (rc != APR_SUCCESS) {
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
msr_log(msr, 1, "collections_remove_stale: Failed to access DBM file \"%s\": %s", log_escape(msr->mp, dbm_filename),
get_apr_error(msr->mp, rc));
dbm = NULL;
Expand All @@ -614,12 +644,6 @@ int collections_remove_stale(modsec_rec *msr, const char *col_name) {

/* First get a list of all keys. */
keys_arr = apr_array_make(msr->mp, 256, sizeof(char *));
rc = apr_sdbm_lock(dbm, APR_FLOCK_SHARED);
if (rc != APR_SUCCESS) {
msr_log(msr, 1, "collections_remove_stale: Failed to lock DBM file \"%s\": %s", log_escape(msr->mp, dbm_filename),
get_apr_error(msr->mp, rc));
goto error;
}

/* No one can write to the file while doing this so
* do it as fast as possible.
Expand All @@ -632,7 +656,6 @@ int collections_remove_stale(modsec_rec *msr, const char *col_name) {
}
rc = apr_sdbm_nextkey(dbm, &key);
}
apr_sdbm_unlock(dbm);

if (msr->txcfg->debuglog_level >= 9) {
msr_log(msr, 9, "collections_remove_stale: Found %d record(s) in file \"%s\".", keys_arr->nelts,
Expand Down Expand Up @@ -698,13 +721,14 @@ int collections_remove_stale(modsec_rec *msr, const char *col_name) {
}

apr_sdbm_close(dbm);

apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
return 1;

error:

if (dbm) {
apr_sdbm_close(dbm);
apr_global_mutex_unlock(msr->modsecurity->dbm_lock);
}

return -1;
Expand Down