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Make accesslist reload thread safe. The last commit actually would make a free possible while another thread was bsearching that memory

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This commit is contained in:
Dirk Engling 2021-04-19 22:33:23 +02:00
parent fde79836e6
commit 102ba9075b
1 changed files with 40 additions and 18 deletions
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58
ot_accesslist.c
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@ -25,19 +25,25 @@
/* GLOBAL VARIABLES */
#ifdef WANT_ACCESSLIST
char *g_accesslist_filename;
static ot_hash *g_accesslist;
static size_t g_accesslist_size;
static pthread_mutex_t g_accesslist_mutex;
typedef struct {
ot_hash *list;
size_t size;
} ot_accesslist;
ot_accesslist * g_accesslist = NULL;
ot_accesslist * g_accesslist_old = NULL;
static int vector_compare_hash(const void *hash1, const void *hash2 ) {
return memcmp( hash1, hash2, OT_HASH_COMPARE_SIZE );
}
/* Read initial access list */
static void accesslist_readfile( void ) {
ot_hash *info_hash, *accesslist_new = NULL, *accesslist_old;
char *map, *map_end, *read_offs;
size_t maplen;
ot_accesslist * accesslist_new = malloc(sizeof(ot_accesslist));
ot_hash *info_hash;
const char *map, *map_end, *read_offs;
size_t maplen;
if( ( map = mmap_read( g_accesslist_filename, &maplen ) ) == NULL ) {
char *wd = getcwd( NULL, 0 );
@ -48,9 +54,11 @@ static void accesslist_readfile( void ) {
/* You need at least 41 bytes to pass an info_hash, make enough room
for the maximum amount of them */
info_hash = accesslist_new = malloc( ( maplen / 41 ) * 20 );
accesslist_new->size = 0;
info_hash = accesslist_new->list = malloc( ( maplen / 41 ) * 20 );
if( !accesslist_new ) {
fprintf( stderr, "Warning: Not enough memory to allocate %zd bytes for accesslist buffer. May succeed later.\n", ( maplen / 41 ) * 20 );
free(accesslist_new);
return;
}
@ -81,28 +89,33 @@ static void accesslist_readfile( void ) {
while( read_offs <= map_end && *(read_offs++) != '\n' );
}
#ifdef _DEBUG
fprintf( stderr, "Added %zd info_hashes to accesslist\n", (size_t)(info_hash - accesslist_new) );
fprintf( stderr, "Added %zd info_hashes to accesslist\n", (size_t)(info_hash - accesslist_new->list) );
#endif
mmap_unmap( map, maplen);
qsort( accesslist_new, info_hash - accesslist_new, sizeof( *info_hash ), vector_compare_hash );
qsort( accesslist_new->list, info_hash - accesslist_new->list, sizeof( *info_hash ), vector_compare_hash );
accesslist_new->size = info_hash - accesslist_new->list;
/* Now exchange the accesslist vector in the least race condition prone way */
pthread_mutex_lock(&g_accesslist_mutex);
accesslist_old = g_accesslist; /* Keep a copy for later free */
g_accesslist_size = 0; /* Set size to 0 to prevent clients from searching through uninitialised memory */
g_accesslist = accesslist_new; /* Only now set a new list */
g_accesslist_size = info_hash - accesslist_new; /* And finally store it's size */
free(g_accesslist_old); /* If new list is active, the old one can be destroyed */
if (g_accesslist_old) {
free(g_accesslist_old->list);
free(g_accesslist_old);
}
g_accesslist_old = g_accesslist; /* Keep a copy for later free */
g_accesslist = accesslist_new; /* Only now set a new list */
pthread_mutex_unlock(&g_accesslist_mutex);
}
int accesslist_hashisvalid( ot_hash hash ) {
void *exactmatch;
/* Get working copy of current access list */
ot_accesslist * accesslist = g_accesslist;
exactmatch = bsearch( hash, g_accesslist, g_accesslist_size, OT_HASH_COMPARE_SIZE, vector_compare_hash );
void * exactmatch = bsearch( hash, accesslist->list, accesslist->size, OT_HASH_COMPARE_SIZE, vector_compare_hash );
#ifdef WANT_ACCESSLIST_BLACK
return exactmatch == NULL;
@ -140,9 +153,18 @@ void accesslist_init( ) {
void accesslist_deinit( void ) {
pthread_cancel( thread_id );
pthread_mutex_destroy(&g_accesslist_mutex);
free( g_accesslist );
g_accesslist = 0;
g_accesslist_size = 0;
if (g_accesslist_old) {
free(g_accesslist_old->list);
free(g_accesslist_old);
g_accesslist_old = 0;
}
if (g_accesslist) {
free(g_accesslist->list);
free(g_accesslist);
g_accesslist = 0;
}
}
#endif