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Commit 2384b0c0 authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Greg Kroah-Hartman
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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: default avatarTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: default avatarsyzbot <syzbot+d29d18215e477cfbfbdd@syzkaller.appspotmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 143b72d6

net/nfc/llcp_commands.c

+6 −3
Original line number Diff line number Diff line
@@ -752,11 +752,14 @@ 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);