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Miller" Subject: [PATCH 4.16 15/81] net: af_packet: fix race in PACKET_{R|T}X_RING Date: Fri, 27 Apr 2018 15:58:17 +0200 Message-Id: <20180427135744.133912226@linuxfoundation.org> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180427135743.216853156@linuxfoundation.org> References: <20180427135743.216853156@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 5171b37d959641bbc619781caf62e61f7b940871 ] In order to remove the race caught by syzbot [1], we need to lock the socket before using po->tp_version as this could change under us otherwise. This means lock_sock() and release_sock() must be done by packet_set_ring() callers. [1] : BUG: KMSAN: uninit-value in packet_set_ring+0x1254/0x3870 net/packet/af_packet.c:4249 CPU: 0 PID: 20195 Comm: syzkaller707632 Not tainted 4.16.0+ #83 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x185/0x1d0 lib/dump_stack.c:53 kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067 __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676 packet_set_ring+0x1254/0x3870 net/packet/af_packet.c:4249 packet_setsockopt+0x12c6/0x5a90 net/packet/af_packet.c:3662 SYSC_setsockopt+0x4b8/0x570 net/socket.c:1849 SyS_setsockopt+0x76/0xa0 net/socket.c:1828 do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 RIP: 0033:0x449099 RSP: 002b:00007f42b5307ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 000000000070003c RCX: 0000000000449099 RDX: 0000000000000005 RSI: 0000000000000107 RDI: 0000000000000003 RBP: 0000000000700038 R08: 000000000000001c R09: 0000000000000000 R10: 00000000200000c0 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000080eecf R14: 00007f42b53089c0 R15: 0000000000000001 Local variable description: ----req_u@packet_setsockopt Variable was created at: packet_setsockopt+0x13f/0x5a90 net/packet/af_packet.c:3612 SYSC_setsockopt+0x4b8/0x570 net/socket.c:1849 Fixes: f6fb8f100b80 ("af-packet: TPACKET_V3 flexible buffer implementation.") Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/packet/af_packet.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3008,6 +3008,7 @@ static int packet_release(struct socket packet_flush_mclist(sk); + lock_sock(sk); if (po->rx_ring.pg_vec) { memset(&req_u, 0, sizeof(req_u)); packet_set_ring(sk, &req_u, 1, 0); @@ -3017,6 +3018,7 @@ static int packet_release(struct socket memset(&req_u, 0, sizeof(req_u)); packet_set_ring(sk, &req_u, 1, 1); } + release_sock(sk); f = fanout_release(sk); @@ -3645,6 +3647,7 @@ packet_setsockopt(struct socket *sock, i union tpacket_req_u req_u; int len; + lock_sock(sk); switch (po->tp_version) { case TPACKET_V1: case TPACKET_V2: @@ -3655,12 +3658,17 @@ packet_setsockopt(struct socket *sock, i len = sizeof(req_u.req3); break; } - if (optlen < len) - return -EINVAL; - if (copy_from_user(&req_u.req, optval, len)) - return -EFAULT; - return packet_set_ring(sk, &req_u, 0, - optname == PACKET_TX_RING); + if (optlen < len) { + ret = -EINVAL; + } else { + if (copy_from_user(&req_u.req, optval, len)) + ret = -EFAULT; + else + ret = packet_set_ring(sk, &req_u, 0, + optname == PACKET_TX_RING); + } + release_sock(sk); + return ret; } case PACKET_COPY_THRESH: { @@ -4210,8 +4218,6 @@ static int packet_set_ring(struct sock * /* Added to avoid minimal code churn */ struct tpacket_req *req = &req_u->req; - lock_sock(sk); - rb = tx_ring ? &po->tx_ring : &po->rx_ring; rb_queue = tx_ring ? &sk->sk_write_queue : &sk->sk_receive_queue; @@ -4349,7 +4355,6 @@ static int packet_set_ring(struct sock * if (pg_vec) free_pg_vec(pg_vec, order, req->tp_block_nr); out: - release_sock(sk); return err; }