Re: [PATCH net v3 2/2] net: rose: fix null-ptr-deref caused by rose_kill_by_neigh
From: Paolo Abeni <pabeni@redhat.com>
Date: 2022-06-28 11:12:54
Also in:
linux-hams, lkml
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
On Fri, 2022-06-24 at 09:05 +0800, Duoming Zhou wrote:
quoted hunk ↗ jump to hunk
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: <TASK> ? __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 <redacted> --- 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