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[188.155.185.9]) by smtp.gmail.com with ESMTPSA id r4sm17199111wre.84.2021.05.31.00.21.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 May 2021 00:21:40 -0700 (PDT) From: Krzysztof Kozlowski To: Krzysztof Kozlowski , "David S. Miller" , Jakub Kicinski , "John W. Linville" , Samuel Ortiz , linux-nfc@lists.01.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Cc: thadeu.cascardo@canonical.com, stable@vger.kernel.org, syzbot+80fb126e7f7d8b1a5914@syzkaller.appspotmail.com, butt3rflyh4ck Subject: [RESEND PATCH] nfc: fix NULL ptr dereference in llcp_sock_getname() after failed connect Date: Mon, 31 May 2021 09:21:38 +0200 Message-Id: <20210531072138.5219-1-krzysztof.kozlowski@canonical.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org It's possible to trigger NULL pointer dereference by local unprivileged user, when calling getsockname() after failed bind() (e.g. the bind fails because LLCP_SAP_MAX used as SAP): BUG: kernel NULL pointer dereference, address: 0000000000000000 CPU: 1 PID: 426 Comm: llcp_sock_getna Not tainted 5.13.0-rc2-next-20210521+ #9 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1 04/01/2014 Call Trace: llcp_sock_getname+0xb1/0xe0 __sys_getpeername+0x95/0xc0 ? lockdep_hardirqs_on_prepare+0xd5/0x180 ? syscall_enter_from_user_mode+0x1c/0x40 __x64_sys_getpeername+0x11/0x20 do_syscall_64+0x36/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xae This can be reproduced with Syzkaller C repro (bind followed by getpeername): https://syzkaller.appspot.com/x/repro.c?x=14def446e00000 Cc: Fixes: d646960f7986 ("NFC: Initial LLCP support") Reported-by: syzbot+80fb126e7f7d8b1a5914@syzkaller.appspotmail.com Reported-by: butt3rflyh4ck Signed-off-by: Krzysztof Kozlowski --- Not extensively tested yet but fixes this particular issue. Reason for resend: 1. Keep it public. --- net/nfc/llcp_sock.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/nfc/llcp_sock.c b/net/nfc/llcp_sock.c index 53dbe733f998..6cfd30fc0798 100644 --- a/net/nfc/llcp_sock.c +++ b/net/nfc/llcp_sock.c @@ -110,6 +110,7 @@ static int llcp_sock_bind(struct socket *sock, struct sockaddr *addr, int alen) if (!llcp_sock->service_name) { nfc_llcp_local_put(llcp_sock->local); llcp_sock->local = NULL; + llcp_sock->dev = NULL; ret = -ENOMEM; goto put_dev; } @@ -119,6 +120,7 @@ static int llcp_sock_bind(struct socket *sock, struct sockaddr *addr, int alen) llcp_sock->local = NULL; kfree(llcp_sock->service_name); llcp_sock->service_name = NULL; + llcp_sock->dev = NULL; ret = -EADDRINUSE; goto put_dev; }