From nobody Thu Apr 16 02:04:34 2026 Received: from m16.mail.163.com (m16.mail.163.com [117.135.210.5]) (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 009CF29A2; Tue, 3 Mar 2026 07:45:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.5 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772523953; cv=none; b=miiqKOB5JmsEtNQiVywhXbGRlGGxPtQKnSxb239gJ8Saz8SFpniu2QckQ94Fy+ejcyao7L7/Lb4co+P29BHxdJjMadRGU2P3KqANGyAmCyWiCacohFL1/SO9VXOP63MUnPCbuKEMUY9MPkAQru6SXOF7gUnqVrzf9o7WMxXfiaE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772523953; c=relaxed/simple; bh=B9KK+5v5qrWO0rkxw5Wv/C37WTrWF8ca7NsgsFukjUQ=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=fmVKE4mpg+ZmUvTrSYPeP1j07i82xQfM9qgsdVFoSwaByzgvjm2BmGs/xHWFCcoAaspJGCA3sKOV5S2eXwX63g8rJ/L2JKITWeRPyKXUjUGc4veqg8FkbY4QEDRE8p3FmO/zLcHHrjP5nz3/AU6UMdo779/WkIo9ZLlvep6nbbs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=cYqVJvzD; arc=none smtp.client-ip=117.135.210.5 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="cYqVJvzD" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=oy 8MJl1zCIP4TUwaFErabER2ZVFoaj+u6/XpWLhh5Xs=; b=cYqVJvzDKLJi72s+8i FsUdN3c6xP88AZllnpdlK06xxEB5QgQa3cH4IsKHqfKkCOiOvnnshtR1rvczVECx k+ammi9qriQq2cCTkrW5pAHy0+rkUwTlwHzcI0eyuhUHMqgHsXTJpAcTankfhvFE mQgxx52NAg1zT4eijugStum0g= Received: from localhost.localdomain (unknown []) by gzga-smtp-mtada-g1-3 (Coremail) with SMTP id _____wAXXjhXkaZpm2IBPA--.46718S3; Tue, 03 Mar 2026 15:44:27 +0800 (CST) From: Feng Yang To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, posk@google.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, yangfeng59949@163.com Subject: [PATCH v9 bpf-next 1/2] bpf: test_run: Fix the null pointer dereference issue in bpf_lwt_xmit_push_encap Date: Tue, 3 Mar 2026 15:44:22 +0800 Message-Id: <20260303074423.172680-2-yangfeng59949@163.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260303074423.172680-1-yangfeng59949@163.com> References: <20260303074423.172680-1-yangfeng59949@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: _____wAXXjhXkaZpm2IBPA--.46718S3 X-Coremail-Antispam: 1Uf129KBjvJXoWxAF4UWFy5ZF1Utr1UWryfZwb_yoWrWw1UpF WUtrWFgrs5A340qF48Jr4UXw1YvFWvyFW5Xr1avw1jqF1jqr17Xr1ftF4jqrZ8Ar45uF4x J34Ut3Z7tr1UJaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x0piTmhrUUUUU= X-CM-SenderInfo: p1dqww5hqjkmqzuzqiywtou0bp/xtbC0Bt+9mmmkVts3gAA30 Content-Type: text/plain; charset="utf-8" From: Feng Yang The bpf_lwt_xmit_push_encap helper needs to access skb_dst(skb)->dev to calculate the needed headroom: err =3D skb_cow_head(skb, len + LL_RESERVED_SPACE(skb_dst(skb)->dev)); But skb->_skb_refdst may not be initialized when the skb is set up by bpf_prog_test_run_skb function. Executing bpf_lwt_push_ip_encap function in this scenario will trigger null pointer dereference, causing a kernel crash as Yinhao reported: [ 105.186365] BUG: kernel NULL pointer dereference, address: 0000000000000= 000 [ 105.186382] #PF: supervisor read access in kernel mode [ 105.186388] #PF: error_code(0x0000) - not-present page [ 105.186393] PGD 121d3d067 P4D 121d3d067 PUD 106c83067 PMD 0 [ 105.186404] Oops: 0000 [#1] PREEMPT SMP NOPTI [ 105.186412] CPU: 3 PID: 3250 Comm: poc Kdump: loaded Not tainted 6.19.0-= rc5 #1 [ 105.186423] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.1= 6.3-debian-1.16.3-2 04/01/2014 [ 105.186427] RIP: 0010:bpf_lwt_push_ip_encap+0x1eb/0x520 [ 105.186443] Code: 0f 84 de 01 00 00 0f b7 4a 04 66 85 c9 0f 85 47 01 00 = 00 31 c0 5b 5d 41 5c 41 5d 41 5e c3 cc cc cc cc 48 8b 73 58 48 83 e6 fe <48= > 8b 36 0f b7 be ec 00 00 00 0f b7 b6 e6 00 00 00 01 fe 83 e6 f0 [ 105.186449] RSP: 0018:ffffbb0e0387bc50 EFLAGS: 00010246 [ 105.186455] RAX: 000000000000004e RBX: ffff94c74e036500 RCX: ffff94c7487= 4da00 [ 105.186460] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff94c74e0= 36500 [ 105.186463] RBP: 0000000000000001 R08: 0000000000000002 R09: 00000000000= 00000 [ 105.186467] R10: ffffbb0e0387bd50 R11: 0000000000000000 R12: ffffbb0e038= 7bc98 [ 105.186471] R13: 0000000000000014 R14: 0000000000000000 R15: 00000000000= 00002 [ 105.186484] FS: 00007f166aa4d680(0000) GS:ffff94c8b7780000(0000) knlGS:= 0000000000000000 [ 105.186490] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 105.186494] CR2: 0000000000000000 CR3: 000000015eade001 CR4: 00000000007= 70ee0 [ 105.186499] PKRU: 55555554 [ 105.186502] Call Trace: [ 105.186507] [ 105.186513] bpf_lwt_xmit_push_encap+0x2b/0x40 [ 105.186522] bpf_prog_a75eaad51e517912+0x41/0x49 [ 105.186536] ? kvm_clock_get_cycles+0x18/0x30 [ 105.186547] ? ktime_get+0x3c/0xa0 [ 105.186554] bpf_test_run+0x195/0x320 [ 105.186563] ? bpf_test_run+0x10f/0x320 [ 105.186579] bpf_prog_test_run_skb+0x2f5/0x4f0 [ 105.186590] __sys_bpf+0x69c/0xa40 [ 105.186603] __x64_sys_bpf+0x1e/0x30 [ 105.186611] do_syscall_64+0x59/0x110 [ 105.186620] entry_SYSCALL_64_after_hwframe+0x76/0xe0 [ 105.186649] RIP: 0033:0x7f166a97455d Temporarily add the setting of skb->_skb_refdst before bpf_test_run to reso= lve the issue. Fixes: 52f278774e79 ("bpf: implement BPF_LWT_ENCAP_IP mode in bpf_lwt_push_= encap") Reported-by: Yinhao Hu Reported-by: Kaiyan Mei Closes: https://groups.google.com/g/hust-os-kernel-patches/c/8-a0kPpBW2s Signed-off-by: Yun Lu Signed-off-by: Feng Yang Tested-by: syzbot@syzkaller.appspotmail.com --- net/bpf/test_run.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 178c4738e63b..a086cee1ac6a 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -1156,6 +1156,23 @@ int bpf_prog_test_run_skb(struct bpf_prog *prog, con= st union bpf_attr *kattr, skb->ip_summed =3D CHECKSUM_COMPLETE; } =20 + if (prog->type =3D=3D BPF_PROG_TYPE_LWT_XMIT) { + ret =3D -EOPNOTSUPP; + +#if IS_ENABLED(CONFIG_IPV6) + if (ipv6_bpf_stub) { + dst_hold(&net->ipv6.ip6_null_entry->dst); + skb_dst_set(skb, &net->ipv6.ip6_null_entry->dst); + } else { + pr_warn_once("Please test this program with the IPv6 module loaded\n"); + goto out; + } +#else + pr_warn_once("Please test this program with the IPv6 module enabled\n"); + goto out; +#endif + } + ret =3D bpf_test_run(prog, skb, repeat, &retval, &duration, false); if (ret) goto out; --=20 2.43.0 From nobody Thu Apr 16 02:04:34 2026 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.4]) (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 44E782D8393; Tue, 3 Mar 2026 07:45:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.4 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772523929; cv=none; b=PZKqX2a3yp6UBSI5TV6DFsgH22TUugmNIpC1nGdBDjVPvoGDaJeTYzJhTJwQkFgiGpU5mlwt1eUpgVajqtrCGKtK13ujh7++vRJmvK+34GyMVjN2bX5bLljBPMc8c3TLQdu+SIVxnFU3v2s3TUc4212xne/Xd2CVmamfqbIbyJE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772523929; c=relaxed/simple; bh=LDZ94JtoHMM1UEYU5Q90klCQ7sVAFPEQpBpyLjSIKFY=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ri43N5Q53fT5mEwMbCQb/9nLCDLeX4LuP1iFNNBgm+hHZDWveNFLH2XtX8elZqaVCtpjERJljvaABKKe/J0EYPxqGglzTdqTbPbUp//6WOnMdhlPTGRobcaqijLmV1LxQKeE6H3nEMcrAXEI8PhUAV0Dn33Cnd51uYOU3kk+ZVs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=fTDaUN37; arc=none smtp.client-ip=220.197.31.4 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="fTDaUN37" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=4e RwFhUgku6857Z68xn0kodvZ/XzFvUeVFNaJo7REB4=; b=fTDaUN37j7LQblpzhQ DbPHjErirghu2RARK1IMFY/2gwP6hORlyqk715+iS8srriwnvY3rOV6WTq9bvhT7 HVjCiKIpaonK5dssYzDa+C1GwzOgn+q8g/GFeMgZBnijxDNspue4cWTerH7A1QAK HcZbdUhEQ5p3SzmXmv4VZ+740= Received: from localhost.localdomain (unknown []) by gzga-smtp-mtada-g1-3 (Coremail) with SMTP id _____wAXXjhXkaZpm2IBPA--.46718S4; Tue, 03 Mar 2026 15:44:28 +0800 (CST) From: Feng Yang To: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, posk@google.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com Cc: bpf@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, yangfeng59949@163.com Subject: [PATCH v9 bpf-next 2/2] selftests/bpf: Add selftests for the invocation of bpf_lwt_xmit_push_encap Date: Tue, 3 Mar 2026 15:44:23 +0800 Message-Id: <20260303074423.172680-3-yangfeng59949@163.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20260303074423.172680-1-yangfeng59949@163.com> References: <20260303074423.172680-1-yangfeng59949@163.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: _____wAXXjhXkaZpm2IBPA--.46718S4 X-Coremail-Antispam: 1Uf129KBjvdXoW7XF4kCFWxXF4rArW3Wr48JFb_yoWkWrg_tr sYga4kCrWxGFnIyayjkr1UCryakwsxWr9rJFsrJr1kCw4UX3Z8GFs7Gr1DJas2g3y3Kr9x Aa909F1Iyr42qjkaLaAFLSUrUUUUjb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUvcSsGvfC2KfnxnUUI43ZEXa7sRA73vDUUUUU== X-CM-SenderInfo: p1dqww5hqjkmqzuzqiywtou0bp/xtbC0Bx-92mmkVxs5QAA3P Content-Type: text/plain; charset="utf-8" From: Feng Yang Calling bpf_lwt_xmit_push_encap will not cause a crash when dst is missing. Signed-off-by: Feng Yang --- .../selftests/bpf/progs/verifier_lwt.c | 20 +++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/tools/testing/selftests/bpf/progs/verifier_lwt.c b/tools/testi= ng/selftests/bpf/progs/verifier_lwt.c index 5ab746307309..9cef07e6eceb 100644 --- a/tools/testing/selftests/bpf/progs/verifier_lwt.c +++ b/tools/testing/selftests/bpf/progs/verifier_lwt.c @@ -231,4 +231,24 @@ __naked void not_permitted_for_lwt_prog(void) : __clobber_all); } =20 +SEC("lwt_xmit") +__description("missing dst when calling bpf_lwt_xmit_push_encap") +__success __retval(0) +__naked void missing_dst_call_bpf_lwt_xmit_push_encap(void) +{ + asm volatile (" \ + r9 =3D 69; \ + r3 =3D r10; \ + r3 +=3D -32; \ + *(u64 *)(r3 + 0) =3D r9; \ + r2 =3D 2; \ + r4 =3D 20; \ + call %[bpf_lwt_push_encap]; \ + r0 =3D 0; \ + exit; \ +" : + : __imm(bpf_lwt_push_encap) + : __clobber_all); +} + char _license[] SEC("license") =3D "GPL"; --=20 2.43.0