| Message ID | 20220629104941.26351-1-duoming@zju.edu.cn (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [v4] net: rose: fix null-ptr-deref caused by rose_kill_by_neigh | expand |
On Wed, 29 Jun 2022 18:49:41 +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) > if (rose->neighbour == neigh) { Why is it okay to perform this comparison without the socket lock, if we need a socket lock to clear it? Looks like rose_kill_by_neigh() is not guaranteed to clear all the uses of a neighbor. > + sock_hold(s); > + spin_unlock_bh(&rose_list_lock); > + lock_sock(s); > rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0); > rose->neighbour->use--; What protects the use counter? > rose->neighbour = NULL; > + release_sock(s); > + spin_lock_bh(&rose_list_lock); Don't take the lock here just dump one line further back. > + sock_put(s); > + goto again; > } > } > spin_unlock_bh(&rose_list_lock); > diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c > index fee6409c2bb..b116828b422 100644 > --- a/net/rose/rose_route.c > +++ b/net/rose/rose_route.c > @@ -827,7 +827,9 @@ void rose_link_failed(ax25_cb *ax25, int reason) > ax25_cb_put(ax25); > > rose_del_route_by_neigh(rose_neigh); > + spin_unlock_bh(&rose_neigh_list_lock); > rose_kill_by_neigh(rose_neigh); > + return; > } > spin_unlock_bh(&rose_neigh_list_lock); > }
Hello, On Fri, 1 Jul 2022 19:41:55 -0700 Jakub Kicinski wrote: > On Wed, 29 Jun 2022 18:49:41 +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) > > > if (rose->neighbour == neigh) { > > Why is it okay to perform this comparison without the socket lock, > if we need a socket lock to clear it? Looks like rose_kill_by_neigh() > is not guaranteed to clear all the uses of a neighbor. I am sorry, the comparision should also be protected with socket lock. The rose_kill_by_neigh() only clear the neighbor that is passed as parameter of rose_kill_by_neigh(). > > + sock_hold(s); > > + spin_unlock_bh(&rose_list_lock); > > + lock_sock(s); > > rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0); > > rose->neighbour->use--; > > What protects the use counter? The use coounter is protected by socket lock. > > rose->neighbour = NULL; > > + release_sock(s); > > + spin_lock_bh(&rose_list_lock); > > Don't take the lock here just dump one line further back. Ok, I will dump one line further back. Best regards, Duoming Zhou
On Sat, 2 Jul 2022 15:23:57 +0800 (GMT+08:00) duoming@zju.edu.cn wrote: > > On Wed, 29 Jun 2022 18:49:41 +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) > > > > > if (rose->neighbour == neigh) { > > > > Why is it okay to perform this comparison without the socket lock, > > if we need a socket lock to clear it? Looks like rose_kill_by_neigh() > > is not guaranteed to clear all the uses of a neighbor. > > I am sorry, the comparision should also be protected with socket lock. > The rose_kill_by_neigh() only clear the neighbor that is passed as > parameter of rose_kill_by_neigh(). Don't think that's possible, you'd have to drop the neigh lock every time. > > > + sock_hold(s); > > > + spin_unlock_bh(&rose_list_lock); > > > + lock_sock(s); > > > rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0); > > > rose->neighbour->use--; > > > > What protects the use counter? > > The use coounter is protected by socket lock. Which one, the neigh object can be shared by multiple sockets, no?
Hello, On Sat, 2 Jul 2022 12:01:08 -0700 Jakub Kicinski wrote: > On Sat, 2 Jul 2022 15:23:57 +0800 (GMT+08:00) duoming@zju.edu.cn wrote: > > > On Wed, 29 Jun 2022 18:49:41 +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) > > > > > > > if (rose->neighbour == neigh) { > > > > > > Why is it okay to perform this comparison without the socket lock, > > > if we need a socket lock to clear it? Looks like rose_kill_by_neigh() > > > is not guaranteed to clear all the uses of a neighbor. > > > > I am sorry, the comparision should also be protected with socket lock. > > The rose_kill_by_neigh() only clear the neighbor that is passed as > > parameter of rose_kill_by_neigh(). > > Don't think that's possible, you'd have to drop the neigh lock every > time. The neighbour is cleared in two situations. (1) When the rose device is down, the rose_link_device_down() traverses the rose_neigh_list and uses the rose_kill_by_neigh() to clear the neighbors of the device. void rose_link_device_down(struct net_device *dev) { struct rose_neigh *rose_neigh; for (rose_neigh = rose_neigh_list; rose_neigh != NULL; rose_neigh = rose_neigh->next) { if (rose_neigh->dev == dev) { rose_del_route_by_neigh(rose_neigh); rose_kill_by_neigh(rose_neigh); } } } https://elixir.bootlin.com/linux/v5.19-rc4/source/net/rose/rose_route.c#L839 (2) When the level 2 link has timed out, the rose_link_failed() calls rose_kill_by_neigh() to clear the rose_neigh. https://elixir.bootlin.com/linux/v5.19-rc4/source/net/rose/rose_route.c#L813 > > > > + sock_hold(s); > > > > + spin_unlock_bh(&rose_list_lock); > > > > + lock_sock(s); > > > > rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0); > > > > rose->neighbour->use--; > > > > > > What protects the use counter? > > > > The use counter is protected by socket lock. > > Which one, the neigh object can be shared by multiple sockets, no? The sk_for_each() traverses the rose_list and uses the lock of the socket that is extracted from the rose_list to protect the use counter. diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c index bf2d986a6bc..6d5088b030a 100644 --- a/net/rose/af_rose.c +++ b/net/rose/af_rose.c @@ -165,14 +165,26 @@ void rose_kill_by_neigh(struct rose_neigh *neigh) struct sock *s; spin_lock_bh(&rose_list_lock); +again: sk_for_each(s, &rose_list) { struct rose_sock *rose = rose_sk(s); + sock_hold(s); + spin_unlock_bh(&rose_list_lock); + lock_sock(s); if (rose->neighbour == neigh) { rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0); rose->neighbour->use--; rose->neighbour = NULL; + release_sock(s); + sock_put(s); + spin_lock_bh(&rose_list_lock); + goto again; } + release_sock(s); + sock_put(s); + spin_lock_bh(&rose_list_lock); + goto again; } spin_unlock_bh(&rose_list_lock); } Best regards, Duoming Zhou
diff --git a/net/rose/af_rose.c b/net/rose/af_rose.c index bf2d986a6bc..24dcbde88fb 100644 --- a/net/rose/af_rose.c +++ b/net/rose/af_rose.c @@ -165,13 +165,21 @@ void rose_kill_by_neigh(struct rose_neigh *neigh) struct sock *s; spin_lock_bh(&rose_list_lock); +again: sk_for_each(s, &rose_list) { struct rose_sock *rose = rose_sk(s); if (rose->neighbour == neigh) { + sock_hold(s); + spin_unlock_bh(&rose_list_lock); + lock_sock(s); rose_disconnect(s, ENETUNREACH, ROSE_OUT_OF_ORDER, 0); rose->neighbour->use--; rose->neighbour = NULL; + release_sock(s); + spin_lock_bh(&rose_list_lock); + sock_put(s); + goto again; } } spin_unlock_bh(&rose_list_lock); diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c index fee6409c2bb..b116828b422 100644 --- a/net/rose/rose_route.c +++ b/net/rose/rose_route.c @@ -827,7 +827,9 @@ void rose_link_failed(ax25_cb *ax25, int reason) ax25_cb_put(ax25); rose_del_route_by_neigh(rose_neigh); + spin_unlock_bh(&rose_neigh_list_lock); rose_kill_by_neigh(rose_neigh); + return; } spin_unlock_bh(&rose_neigh_list_lock); }
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 <duoming@zju.edu.cn> --- Changes in v4: - v4: Fix traversing erroneously stop problem. net/rose/af_rose.c | 8 ++++++++ net/rose/rose_route.c | 2 ++ 2 files changed, 10 insertions(+)