Messages in this thread Patch in this message | | | From | Duoming Zhou <> | Subject | [PATCH v4] net: rose: fix null-ptr-deref caused by rose_kill_by_neigh | Date | Wed, 29 Jun 2022 18:49:41 +0800 |
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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(+)
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); } -- 2.17.1
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