4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp
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=4a131cc571c3733e0eff6bc673f4e36ae48f19c...
Signed-off-by: Tetsuo Handa penguin-kernel@I-love.SAKURA.ne.jp Reported-by: syzbot syzbot+d29d18215e477cfbfbdd@syzkaller.appspotmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/nfc/llcp_commands.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
--- a/net/nfc/llcp_commands.c +++ b/net/nfc/llcp_commands.c @@ -754,11 +754,14 @@ int nfc_llcp_send_ui_frame(struct nfc_ll 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);