From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from va-1-112.ptr.blmpb.com (va-1-112.ptr.blmpb.com [209.127.230.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 27E9A4DAFBD for ; Thu, 17 Sep 2026 12:10:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.127.230.112 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789647069; cv=none; b=R3a9BrYTViow3LHkZzKdChHzOnlEDuseK1vzNeNOludFx9KOCL4rxrK1TiQs84MlPdiiylseh0pBkzx+qgGt+MesrkuealOQGakYVgyv5qsVwovCMLU8vRofGG0dxhLVy11/3B7cJ4sWeQru17WmghraOuKbTAVvuhLC1CBv9OQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789647069; c=relaxed/simple; bh=R/LUprRLLIwHn62Aa6X+Qeen23stIshNt80hL1nPc3A=; h=To:Cc:Message-Id:References:Date:Mime-Version:Content-Type:From: Subject:In-Reply-To; b=WomwKxp/hFlR5eVnTpUQjuCxy7w7THPD05R6qRpcYhM+OaoSEjecJJKpvICP34kF78FD876RWsX2dvq7HkV/IwZhPdrC/FywHUAFqLR7wJvJLziwCVjEjOUhM7v/9WGQ+JK17JAhJZQ7I8ejFDTAwZKpJJvMTFoclbqKc15kwko= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com; spf=pass smtp.mailfrom=bytedance.com; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b=eiYvEvni; arc=none smtp.client-ip=209.127.230.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=bytedance.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=bytedance.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=bytedance.com header.i=@bytedance.com header.b="eiYvEvni" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=2212171451; d=bytedance.com; t=1789647046; h=from:subject: mime-version:from:date:message-id:subject:to:cc:reply-to:content-type: mime-version:in-reply-to:message-id; bh=/M6XW7TajI5wGVtKhZBxGWB0mPjI/XpBYPgZ/W1nlaQ=; b=eiYvEvniDk/QnafpoHOXZg2e8cRAS7+or5s6fQLVpUw52Drmwxw+4BDEWuejbElHLkFggy LPjCXo8AQ34r3KqsAYHppkX/kEebXDzFvKSr/TWCzxIYrdZyRNos6oRqLUUANzTFOPmk1X aHi2D1EXcY9IeXTQN/y6T4JRWhUIlzkNh8DTHN5zFjfuzsoSxultY3rQuN3RR1QxKO6ba6 Onx/Ecmb+y5LxWlB6La+TpLB6EOVojFauEL5XJ6UGVmcG0t61zDIUgebTCiCDKb6bw4s/X di30M59xD036NKOwoBxBJkg9LKXfc4vBLqU00gYgSIEtQkAXJdx+hhPGZdOG3A== To: Cc: , , , , , , , , , , , , , "Zhao Gongyi" Message-Id: <20260917121016.48171-1-zhaogongyi@bytedance.com> References: <20260915071743.29394-1-zhaogongyi@bytedance.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) Date: Thu, 17 Sep 2026 20:10:16 +0800 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Lms-Return-Path: Content-Transfer-Encoding: 7bit X-Original-From: Zhao Gongyi Content-Type: text/plain; charset=UTF-8 From: "Zhao Gongyi" Subject: [PATCH bpf v2] bpf, sockmap: reject max_entries > INT_MAX in sock_map_alloc In-Reply-To: <20260915071743.29394-1-zhaogongyi@bytedance.com> From: Zhao Gongyi sock_map_alloc() only rejects max_entries == 0 and otherwise allows any u32 value. sock_map_free() then walks the sks[] array with a signed int iterator: int i; for (i = 0; i < stab->map.max_entries; i++) struct sock **psk = &stab->sks[i]; When a SOCKMAP is created with max_entries = 0xffffffff (UINT_MAX), the allocation of 32 GiB can succeed on large-memory hosts. During free the counter reaches 0x80000000, wraps to INT_MIN, is sign-extended by movslq and turned into a ~16 GiB negative offset from stab->sks, pointing far below the allocation. The faulting access is an xchg() write in sock_map_free(). Without KASAN, the same out-of-bounds write can fault on an unmapped vmalloc page or corrupt an unrelated allocation if that vmalloc address is populated. On a KASAN kernel with CONFIG_KASAN_VMALLOC=y, the shadow check for that address hits an unmapped shadow page and oopses first: BUG: unable to handle page fault for address: fffff521b59c5a00 RIP: 0010:kasan_check_range+0x107/0x190 Call Trace: sock_map_free+0x93/0x190 map_create+0x68d/0xb30 __sys_bpf+0x21e/0x2e70 Vmcore confirmed stab->map.max_entries == 0xffffffff, stab->sks == 0xffffc911ace2d000, and the faulting address sks + (s64)INT_MIN * 8 exactly at 0xffffc90dace2d000. The same buggy path is reached on the normal close()/bpf_map_free_deferred() path whenever such a map is destroyed. sock_map_alloc() used to bound its allocation size through bpf_map_charge_init(), but the bound was dropped when rlimit-based memory accounting was removed. Reject max_entries > INT_MAX at creation time so the signed iterator in sock_map_free() never sees a value that would overflow. Triggered by syzkaller and reproduced on both a 6.6-based KASAN kernel and the upstream v7.3-rc2 kernel. Fixes: 0d2c4f964050 ("bpf: Eliminate rlimit-based memory accounting for sockmap and sockhash maps") Signed-off-by: Zhao Gongyi --- v2: - Correct the Fixes tag to the commit that removed the allocation-size bound. - Clarify that the bug is an out-of-bounds write reachable without KASAN. - Add Daniel Borkmann to Cc. net/core/sock_map.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/core/sock_map.c b/net/core/sock_map.c index ca49bc7f8..38df84284 100644 --- a/net/core/sock_map.c +++ b/net/core/sock_map.c @@ -41,6 +41,7 @@ static struct bpf_map *sock_map_alloc(union bpf_attr *attr) struct bpf_stab *stab; if (attr->max_entries == 0 || + attr->max_entries > INT_MAX || attr->key_size != 4 || (attr->value_size != sizeof(u32) && attr->value_size != sizeof(u64)) || -- 2.39.5 (Apple Git-154)