Core: fixed segfault with too large bucket sizes (ticket #1806).
To save memory hash code uses u_short to store resulting bucket sizes,
so maximum bucket size is limited to 65536 minus ngx_cacheline_size (larger
values will be aligned to 65536 which will overflow u_short). However,
there were no checks to enforce this, and using larger bucket sizes
resulted in overflows and segmentation faults.
Appropriate safety checks to enforce this added to ngx_hash_init().
diff --git a/src/core/ngx_hash.c b/src/core/ngx_hash.c
index 1944c7a..d684e70 100644
--- a/src/core/ngx_hash.c
+++ b/src/core/ngx_hash.c
@@ -265,6 +265,14 @@
return NGX_ERROR;
}
+ if (hinit->bucket_size > 65536 - ngx_cacheline_size) {
+ ngx_log_error(NGX_LOG_EMERG, hinit->pool->log, 0,
+ "could not build %s, too large "
+ "%s_bucket_size: %i",
+ hinit->name, hinit->name, hinit->bucket_size);
+ return NGX_ERROR;
+ }
+
for (n = 0; n < nelts; n++) {
if (hinit->bucket_size < NGX_HASH_ELT_SIZE(&names[n]) + sizeof(void *))
{
@@ -300,17 +308,19 @@
}
key = names[n].key_hash % size;
- test[key] = (u_short) (test[key] + NGX_HASH_ELT_SIZE(&names[n]));
+ len = test[key] + NGX_HASH_ELT_SIZE(&names[n]);
#if 0
ngx_log_error(NGX_LOG_ALERT, hinit->pool->log, 0,
- "%ui: %ui %ui \"%V\"",
- size, key, test[key], &names[n].key);
+ "%ui: %ui %uz \"%V\"",
+ size, key, len, &names[n].key);
#endif
- if (test[key] > (u_short) bucket_size) {
+ if (len > bucket_size) {
goto next;
}
+
+ test[key] = (u_short) len;
}
goto found;
@@ -341,7 +351,17 @@
}
key = names[n].key_hash % size;
- test[key] = (u_short) (test[key] + NGX_HASH_ELT_SIZE(&names[n]));
+ len = test[key] + NGX_HASH_ELT_SIZE(&names[n]);
+
+ if (len > 65536 - ngx_cacheline_size) {
+ ngx_log_error(NGX_LOG_EMERG, hinit->pool->log, 0,
+ "could not build %s, you should "
+ "increase %s_max_size: %i",
+ hinit->name, hinit->name, hinit->max_size);
+ return NGX_ERROR;
+ }
+
+ test[key] = (u_short) len;
}
len = 0;
