From: Tetsuo Handa Date: Wed, 18 Jul 2018 09:57:27 +0000 (+0900) Subject: net/nfc: Avoid stalls when nfc_alloc_send_skb() returned NULL. X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=d31a56d23eac2cc53559731b5a7c17fd1a1b0450;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git net/nfc: Avoid stalls when nfc_alloc_send_skb() returned NULL. commit 3bc53be9db21040b5d2de4d455f023c8c494aa68 upstream. syzbot is reporting stalls at nfc_llcp_send_ui_frame() [1]. This is because nfc_llcp_send_ui_frame() is retrying the loop without any delay when nonblocking nfc_alloc_send_skb() returned NULL. Since there is no need to use MSG_DONTWAIT if we retry until sock_alloc_send_pskb() succeeds, let's use blocking call. Also, in case an unexpected error occurred, let's break the loop if blocking nfc_alloc_send_skb() failed. [1] https://syzkaller.appspot.com/bug?id=4a131cc571c3733e0eff6bc673f4e36ae48f19c6 Signed-off-by: Tetsuo Handa Reported-by: syzbot Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/nfc/llcp_commands.c b/net/nfc/llcp_commands.c index 3f266115294f..04759a0c3273 100644 --- a/net/nfc/llcp_commands.c +++ b/net/nfc/llcp_commands.c @@ -753,11 +753,14 @@ int nfc_llcp_send_ui_frame(struct nfc_llcp_sock *sock, u8 ssap, u8 dsap, pr_debug("Fragment %zd bytes remaining %zd", frag_len, remaining_len); - pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT, + pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, 0, frag_len + LLCP_HEADER_SIZE, &err); if (pdu == NULL) { - pr_err("Could not allocate PDU\n"); - continue; + pr_err("Could not allocate PDU (error=%d)\n", err); + len -= remaining_len; + if (len == 0) + len = err; + break; } pdu = llcp_add_header(pdu, dsap, ssap, LLCP_PDU_UI);