From: Duoming Zhou <duoming@zju.edu.cn> stable inclusion from stable-v5.10.112 commit b20a5ab0f5fb175750c6bafd4cf12daccf00c738 bugzilla: 186602, https://gitee.com/src-openeuler/kernel/issues/I5783H CVE: CVE-2022-1204 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 9fd75b66b8f68498454d685dc4ba13192ae069b0 upstream. The previous commit d01ffb9eee4a ("ax25: add refcount in ax25_dev to avoid UAF bugs") and commit feef318c855a ("ax25: fix UAF bugs of net_device caused by rebinding operation") increase the refcounts of ax25_dev and net_device in ax25_bind() and decrease the matching refcounts in ax25_kill_by_device() in order to prevent UAF bugs, but there are reference count leaks. The root cause of refcount leaks is shown below: (Thread 1) | (Thread 2) ax25_bind() | ... | ax25_addr_ax25dev() | ax25_dev_hold() //(1) | ... | dev_hold_track() //(2) | ... | ax25_destroy_socket() | ax25_cb_del() | ... | hlist_del_init() //(3) | | (Thread 3) | ax25_kill_by_device() | ... | ax25_for_each(s, &ax25_list) { | if (s->ax25_dev == ax25_dev) //(4) | ... | Firstly, we use ax25_bind() to increase the refcount of ax25_dev in position (1) and increase the refcount of net_device in position (2). Then, we use ax25_cb_del() invoked by ax25_destroy_socket() to delete ax25_cb in hlist in position (3) before calling ax25_kill_by_device(). Finally, the decrements of refcounts in ax25_kill_by_device() will not be executed, because no s->ax25_dev equals to ax25_dev in position (4). This patch adds decrements of refcounts in ax25_release() and use lock_sock() to do synchronization. If refcounts decrease in ax25_release(), the decrements of refcounts in ax25_kill_by_device() will not be executed and vice versa. Fixes: d01ffb9eee4a ("ax25: add refcount in ax25_dev to avoid UAF bugs") Fixes: 87563a043cef ("ax25: fix reference count leaks of ax25_dev") Fixes: feef318c855a ("ax25: fix UAF bugs of net_device caused by rebinding operation") Reported-by: Thomas Osterried <thomas@osterried.de> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> Signed-off-by: David S. Miller <davem@davemloft.net> [OP: backport to 5.10: adjust dev_put_track()->dev_put()] Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> conflict: net/ax25/af_ax25.c Signed-off-by: Lu Wei <luwei32@huawei.com> Reviewed-by: Wei Yongjun <weiyongjun1@huawei.com> Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> --- net/ax25/af_ax25.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 2ec490904d86..b16d466b3983 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -99,8 +99,10 @@ static void ax25_kill_by_device(struct net_device *dev) lock_sock(sk); ax25_disconnect(s, ENETUNREACH); s->ax25_dev = NULL; - dev_put(ax25_dev->dev); - ax25_dev_put(ax25_dev); + if (sk->sk_socket) { + dev_put(ax25_dev->dev); + ax25_dev_put(ax25_dev); + } release_sock(sk); spin_lock_bh(&ax25_list_lock); sock_put(sk); @@ -978,14 +980,20 @@ static int ax25_release(struct socket *sock) { struct sock *sk = sock->sk; ax25_cb *ax25; + ax25_dev *ax25_dev; if (sk == NULL) return 0; sock_hold(sk); - sock_orphan(sk); lock_sock(sk); + sock_orphan(sk); ax25 = sk_to_ax25(sk); + ax25_dev = ax25->ax25_dev; + if (ax25_dev) { + dev_put(ax25_dev->dev); + ax25_dev_put(ax25_dev); + } if (sk->sk_type == SOCK_SEQPACKET) { switch (ax25->state) { -- 2.20.1