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Core: fixed segfault with too large bucket sizes (ticket #1806).

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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().
This commit is contained in:
Maxim Dounin 2019-07-18 18:27:44 +03:00
parent 676d1a0e94
commit 551640703a
1 changed files with 25 additions and 5 deletions
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30
src/core/ngx_hash.c
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@ -265,6 +265,14 @@ ngx_hash_init(ngx_hash_init_t *hinit, ngx_hash_key_t *names, ngx_uint_t nelts)
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 @@ ngx_hash_init(ngx_hash_init_t *hinit, ngx_hash_key_t *names, ngx_uint_t nelts)
}
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 @@ found:
}
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;