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[79.46.200.178]) by smtp.gmail.com with ESMTPSA id w20-20020a05620a0e9400b006b8f8e9bd00sm8365097qkm.5.2022.08.08.00.55.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Aug 2022 00:55:41 -0700 (PDT) Date: Mon, 8 Aug 2022 09:55:33 +0200 From: Stefano Garzarella To: Peilin Ye Cc: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Peilin Ye , George Zhang , Dmitry Torokhov , Andy King , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net v2 1/2] vsock: Fix memory leak in vsock_connect() Message-ID: <20220808075533.p7pczlnixb2phrun@sgarzare-redhat> References: <20220804020925.32167-1-yepeilin.cs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sun, Aug 07, 2022 at 02:00:11AM -0700, Peilin Ye wrote: >From: Peilin Ye > >An O_NONBLOCK vsock_connect() request may try to reschedule >@connect_work. Imagine the following sequence of vsock_connect() >requests: > > 1. The 1st, non-blocking request schedules @connect_work, which will > expire after 200 jiffies. Socket state is now SS_CONNECTING; > > 2. Later, the 2nd, blocking request gets interrupted by a signal after > a few jiffies while waiting for the connection to be established. > Socket state is back to SS_UNCONNECTED, but @connect_work is still > pending, and will expire after 100 jiffies. > > 3. Now, the 3rd, non-blocking request tries to schedule @connect_work > again. Since @connect_work is already scheduled, > schedule_delayed_work() silently returns. sock_hold() is called > twice, but sock_put() will only be called once in > vsock_connect_timeout(), causing a memory leak reported by syzbot: > > BUG: memory leak > unreferenced object 0xffff88810ea56a40 (size 1232): > comm "syz-executor756", pid 3604, jiffies 4294947681 (age 12.350s) > hex dump (first 32 bytes): > 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > 28 00 07 40 00 00 00 00 00 00 00 00 00 00 00 00 (..@............ > backtrace: > [] sk_prot_alloc+0x3e/0x1b0 net/core/sock.c:1930 > [] sk_alloc+0x32/0x2e0 net/core/sock.c:1989 > [] __vsock_create.constprop.0+0x38/0x320 net/vmw_vsock/af_vsock.c:734 > [] vsock_create+0xc1/0x2d0 net/vmw_vsock/af_vsock.c:2203 > [] __sock_create+0x1ab/0x2b0 net/socket.c:1468 > [] sock_create net/socket.c:1519 [inline] > [] __sys_socket+0x6f/0x140 net/socket.c:1561 > [] __do_sys_socket net/socket.c:1570 [inline] > [] __se_sys_socket net/socket.c:1568 [inline] > [] __x64_sys_socket+0x1a/0x20 net/socket.c:1568 > [] do_syscall_x64 arch/x86/entry/common.c:50 [inline] > [] do_syscall_64+0x35/0x80 arch/x86/entry/common.c:80 > [] entry_SYSCALL_64_after_hwframe+0x44/0xae > <...> > >Use mod_delayed_work() instead: if @connect_work is already scheduled, >reschedule it, and undo sock_hold() to keep the reference count >balanced. > >Reported-and-tested-by: syzbot+b03f55bf128f9a38f064@syzkaller.appspotmail.com >Fixes: d021c344051a ("VSOCK: Introduce VM Sockets") >Co-developed-by: Stefano Garzarella >Signed-off-by: Stefano Garzarella >Signed-off-by: Peilin Ye >--- >change since v1: > - merged with Stefano's patch [1] > >[1] https://gitlab.com/sgarzarella/linux/-/commit/2d0f0b9cbbb30d58fdcbca7c1a857fd8f3110d61 > >Hi Stefano, > >About the Fixes: tag, [2] introduced @connect_work, but all it did was >breaking @dwork into two and moving some INIT_DELAYED_WORK()'s, so I don't >think [2] introduced this memory leak? > >Since [2] has already been backported to 4.9 and 4.14, I think we can >Fixes: commit d021c344051a ("VSOCK: Introduce VM Sockets"), too, to make >backporting easier? Yep, I think it should be fine! > >[2] commit 455f05ecd2b2 ("vsock: split dwork to avoid reinitializations") > >Thanks, >Peilin Ye > > net/vmw_vsock/af_vsock.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >index f04abf662ec6..fe14f6cbca22 100644 >--- a/net/vmw_vsock/af_vsock.c >+++ b/net/vmw_vsock/af_vsock.c >@@ -1391,7 +1391,13 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr, > * timeout fires. > */ > sock_hold(sk); >- schedule_delayed_work(&vsk->connect_work, timeout); >+ >+ /* If the timeout function is already scheduled, >+ * reschedule it, then ungrab the socket refcount to >+ * keep it balanced. >+ */ >+ if (mod_delayed_work(system_wq, &vsk->connect_work, timeout)) ^ Checkpatch warns here about line lenght. If you have to re-send, please split it. Anyway, the patch LGTM: Reviewed-by: Stefano Garzarella Thanks, Stefano