From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83F0913B5B9; Thu, 11 Apr 2024 10:08:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712830087; cv=none; b=aryrsNkmvDFSvxMvTyB0RTFyocTLzpscu6+AnjyL0m5OE8oYqukz/NX7XvW6T0kzmZSHOGlpYEBjhILZkyAWvY3hIb2BhliKFHK2lMNTfG0RlNtMCm4oXaI62PTqDTqQG3H4RIFzR5qU1Wl1R/UztCxfWm57sBRo1c4PB+ooTh8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712830087; c=relaxed/simple; bh=d275yoIS5cNyQyj4X2Q4xKdNEmeh96bb/TQO8TTnrfA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Jei+PpwiUSjFph/FHAwNm6+2kRDIa1/ejPMKa2SxXYRs5okF8nCz2XxdEPW+sLLOn5cAf63FkmUArt9veUJygtGQvhc4Bqzm/aGRIUTG4hlC7K01UM1cT2yFMZGONqyF/udKE/XkQM94TNL+5c/I/WDX7YkENgTSrqrul/FhQfk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WNajBqxC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="WNajBqxC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 01D9DC433F1; Thu, 11 Apr 2024 10:08:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1712830087; bh=d275yoIS5cNyQyj4X2Q4xKdNEmeh96bb/TQO8TTnrfA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WNajBqxCx0LlGgqLA570do5ODedSaeOZ6dSj5W6R8Xq3SjW5WrY4/kudK3JFiCx6V daWOwX1bFs/JUOLIXg0F+Ob5bi+uMCSqv2Uvb3UWTRYMBrLo0ElVTh2CFceY+blgEk N24/0APNiUuefJECF8hp5PB8V/Tc/79ki3jR217E= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Florian Westphal , Simon Horman , Paolo Abeni , Sasha Levin Subject: [PATCH 6.8 030/143] net: skbuff: add overflow debug check to pull/push helpers Date: Thu, 11 Apr 2024 11:54:58 +0200 Message-ID: <20240411095421.819736748@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240411095420.903937140@linuxfoundation.org> References: <20240411095420.903937140@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Florian Westphal [ Upstream commit 219eee9c0d16f1b754a8b85275854ab17df0850a ] syzbot managed to trigger following splat: BUG: KASAN: use-after-free in __skb_flow_dissect+0x4a3b/0x5e50 Read of size 1 at addr ffff888208a4000e by task a.out/2313 [..] __skb_flow_dissect+0x4a3b/0x5e50 __skb_get_hash+0xb4/0x400 ip_tunnel_xmit+0x77e/0x26f0 ipip_tunnel_xmit+0x298/0x410 .. Analysis shows that the skb has a valid ->head, but bogus ->data pointer. skb->data gets its bogus value via the neigh layer, which does: 1556 __skb_pull(skb, skb_network_offset(skb)); ... and the skb was already dodgy at this point: skb_network_offset(skb) returns a negative value due to an earlier overflow of skb->network_header (u16). __skb_pull thus "adjusts" skb->data by a huge offset, pointing outside skb->head area. Allow debug builds to splat when we try to pull/push more than INT_MAX bytes. After this, the syzkaller reproducer yields a more precise splat before the flow dissector attempts to read off skb->data memory: WARNING: CPU: 5 PID: 2313 at include/linux/skbuff.h:2653 neigh_connected_output+0x28e/0x400 ip_finish_output2+0xb25/0xed0 iptunnel_xmit+0x4ff/0x870 ipgre_xmit+0x78e/0xbb0 Signed-off-by: Florian Westphal Reviewed-by: Simon Horman Link: https://lore.kernel.org/r/20240216113700.23013-1-fw@strlen.de Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- include/linux/skbuff.h | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 227f4514476b1..741115aeca2f1 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -2637,6 +2637,8 @@ static inline void skb_put_u8(struct sk_buff *skb, u8 val) void *skb_push(struct sk_buff *skb, unsigned int len); static inline void *__skb_push(struct sk_buff *skb, unsigned int len) { + DEBUG_NET_WARN_ON_ONCE(len > INT_MAX); + skb->data -= len; skb->len += len; return skb->data; @@ -2645,6 +2647,8 @@ static inline void *__skb_push(struct sk_buff *skb, unsigned int len) void *skb_pull(struct sk_buff *skb, unsigned int len); static inline void *__skb_pull(struct sk_buff *skb, unsigned int len) { + DEBUG_NET_WARN_ON_ONCE(len > INT_MAX); + skb->len -= len; if (unlikely(skb->len < skb->data_len)) { #if defined(CONFIG_DEBUG_NET) @@ -2669,6 +2673,8 @@ void *__pskb_pull_tail(struct sk_buff *skb, int delta); static inline enum skb_drop_reason pskb_may_pull_reason(struct sk_buff *skb, unsigned int len) { + DEBUG_NET_WARN_ON_ONCE(len > INT_MAX); + if (likely(len <= skb_headlen(skb))) return SKB_NOT_DROPPED_YET; -- 2.43.0