ce57d6474a
commit 5121197ecc5db58c07da95eb1ff82b98b121a221 upstream.
sk->sk_receive_queue is protected by skb queue lock, but for KCM
sockets its RX path takes mux->rx_lock to protect more than just
skb queue. However, kcm_recvmsg() still only grabs the skb queue
lock, so race conditions still exist.
We can teach kcm_recvmsg() to grab mux->rx_lock too but this would
introduce a potential performance regression as struct kcm_mux can
be shared by multiple KCM sockets.
So we have to enforce skb queue lock in requeue_rx_msgs() and handle
skb peek case carefully in kcm_wait_data(). Fortunately,
skb_recv_datagram() already handles it nicely and is widely used by
other sockets, we can just switch to skb_recv_datagram() after
getting rid of the unnecessary sock lock in kcm_recvmsg() and
kcm_splice_read(). Side note: SOCK_DONE is not used by KCM sockets,
so it is safe to get rid of this check too.
I ran the original syzbot reproducer for 30 min without seeing any
issue.
Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
Reported-by: syzbot+278279efdd2730dd14bf@syzkaller.appspotmail.com
Reported-by: shaozhengchao <shaozhengchao@huawei.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Tom Herbert <tom@herbertland.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Link: https://lore.kernel.org/r/20221114005119.597905-1-xiyou.wangcong@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.