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[146.241.115.110]) by smtp.gmail.com with ESMTPSA id a19-20020a05600c349300b0039db500714fsm17448747wmq.6.2022.06.28.04.12.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jun 2022 04:12:41 -0700 (PDT) Message-ID: Subject: Re: [PATCH net v3 2/2] net: rose: fix null-ptr-deref caused by rose_kill_by_neigh From: Paolo Abeni To: Duoming Zhou , linux-hams@vger.kernel.org Cc: ralf@linux-mips.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 28 Jun 2022 13:12:40 +0200 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 (3.42.4-2.fc35) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2022-06-24 at 09:05 +0800, Duoming Zhou wrote: > When the link layer connection is broken, the rose->neighbour is > set to null. But rose->neighbour could be used by rose_connection() > and rose_release() later, because there is no synchronization among > them. As a result, the null-ptr-deref bugs will happen. > > One of the null-ptr-deref bugs is shown below: > > (thread 1) | (thread 2) > | rose_connect > rose_kill_by_neigh | lock_sock(sk) > spin_lock_bh(&rose_list_lock) | if (!rose->neighbour) > rose->neighbour = NULL;//(1) | > | rose->neighbour->use++;//(2) > > The rose->neighbour is set to null in position (1) and dereferenced > in position (2). > > The KASAN report triggered by POC is shown below: > > KASAN: null-ptr-deref in range [0x0000000000000028-0x000000000000002f] > ... > RIP: 0010:rose_connect+0x6c2/0xf30 > RSP: 0018:ffff88800ab47d60 EFLAGS: 00000206 > RAX: 0000000000000005 RBX: 000000000000002a RCX: 0000000000000000 > RDX: ffff88800ab38000 RSI: ffff88800ab47e48 RDI: ffff88800ab38309 > RBP: dffffc0000000000 R08: 0000000000000000 R09: ffffed1001567062 > R10: dfffe91001567063 R11: 1ffff11001567061 R12: 1ffff11000d17cd0 > R13: ffff8880068be680 R14: 0000000000000002 R15: 1ffff11000d17cd0 > ... > Call Trace: > > ? __local_bh_enable_ip+0x54/0x80 > ? selinux_netlbl_socket_connect+0x26/0x30 > ? rose_bind+0x5b0/0x5b0 > __sys_connect+0x216/0x280 > __x64_sys_connect+0x71/0x80 > do_syscall_64+0x43/0x90 > entry_SYSCALL_64_after_hwframe+0x46/0xb0 > > This patch adds lock_sock() in rose_kill_by_neigh() in order to > synchronize with rose_connect() and rose_release(). > > Meanwhile, this patch adds sock_hold() protected by rose_list_lock > that could synchronize with rose_remove_socket() in order to mitigate > UAF bug caused by lock_sock() we add. > > What's more, there is no need using rose_neigh_list_lock to protect > rose_kill_by_neigh(). Because we have already used rose_neigh_list_lock > to protect the state change of rose_neigh in rose_link_failed(), which > is well synchronized. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Duoming Zhou > --- > Changes since v2: > - v2: Fix refcount leak of sock. > > net/rose/af_rose.c | 6 ++++++ > net/rose/rose_route.c | 2 ++ > 2 files changed, 8 insertions(+) > > diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c > index bf2d986a6bc..5caa222c490 100644 > --- a/net/rose/af_rose.c > +++ b/net/rose/af_rose.c > @@ -169,9 +169,15 @@ void rose_kill_by_neigh(struct rose_neigh *neigh) > struct rose_sock *rose = rose_sk(s); > > if (rose->neighbour == neigh) { > + sock_hold(s); > rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0); > rose->neighbour->use--; > + spin_unlock_bh(&rose_list_lock); > + lock_sock(s); > rose->neighbour = NULL; > + release_sock(s); > + spin_lock_bh(&rose_list_lock); I'm sorry, I likely was not clear enough in my previous reply. This is broken. If a list is [spin_]lock protected, you can't release the lock, reacquire it and continue traversing the list from the [now invalid] same iterator. e.g. if s is removed from the list, even if the sock is not de- allocated due to the addtional refcount, the traversing will errnously stop after this sock, instead of continuing processing the remaining socks in the list. A possible alternative, not even build-tested would be: --- diff --git a/include/net/rose.h b/include/net/rose.h index 0f0a4ce0fee7..090db11d528f 100644 --- a/include/net/rose.h +++ b/include/net/rose.h @@ -145,6 +145,7 @@ struct rose_sock { struct rose_facilities_struct facilities; struct timer_list timer; struct timer_list idletimer; + struct rose_sock *dl_next; }; #define rose_sk(sk) ((struct rose_sock *)(sk)) diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c index 5caa222c490e..01f3c50f0921 100644 --- a/net/rose/af_rose.c +++ b/net/rose/af_rose.c @@ -162,25 +162,32 @@ static void rose_remove_socket(struct sock *sk) */ void rose_kill_by_neigh(struct rose_neigh *neigh) { - struct sock *s; + struct rose_sock *del_list = NULL; + struct sock *s, *tmp; spin_lock_bh(&rose_list_lock); - sk_for_each(s, &rose_list) { + sk_for_each_safe(s, tmp, &rose_list) { struct rose_sock *rose = rose_sk(s); if (rose->neighbour == neigh) { - sock_hold(s); - rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0); - rose->neighbour->use--; - spin_unlock_bh(&rose_list_lock); - lock_sock(s); - rose->neighbour = NULL; - release_sock(s); - spin_lock_bh(&rose_list_lock); - sock_put(s); + __sk_del_node(s); + s->dl_next = del_list; + del_list = s; } } spin_unlock_bh(&rose_list_lock); + + while (del_list) { + s = del_list; + del_list = s->dl_next; + + lock_sock(s); + rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0); + rose->neighbour->use--; + rose->neighbour = NULL; + release_sock(s); + sock_put(s); + } } /* --- Paolo