• John Fastabend's avatar
    bpf: sockmap, fix use after free from sleep in psock backlog workqueue · 635e92cf
    John Fastabend authored
    [ Upstream commit bd95e678e0f6e18351ecdc147ca819145db9ed7b ]
    
    Backlog work for psock (sk_psock_backlog) might sleep while waiting
    for memory to free up when sending packets. However, while sleeping
    the socket may be closed and removed from the map by the user space
    side.
    
    This breaks an assumption in sk_stream_wait_memory, which expects the
    wait queue to be still there when it wakes up resulting in a
    use-after-free shown below. To fix his mark sendmsg as MSG_DONTWAIT
    to avoid the sleep altogether. We already set the flag for the
    sendpage case but we missed the case were sendmsg is used.
    Sockmap is currently the only user of skb_send_sock_locked() so only
    the sockmap paths should be impacted.
    
    ==================================================================
    BUG: KASAN: use-after-free in remove_wait_queue+0x31/0x70
    Write of size 8 at addr ffff888069a0c4e8 by task kworker/0:2/110
    
    CPU: 0 PID: 110 Comm: kworker/0:2 Not tainted 5.0.0-rc2-00335-g28f9d1a3d4fe-dirty #14
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-2.fc27 04/01/2014
    Workqueue: events sk_psock_backlog
    Call Trace:
     print_address_description+0x6e/0x2b0
     ? remove_wait_queue+0x31/0x70
     kasan_report+0xfd/0x177
     ? remove_wait_queue+0x31/0x70
     ? remove_wait_queue+0x31/0x70
     remove_wait_queue+0x31/0x70
     sk_stream_wait_memory+0x4dd/0x5f0
     ? sk_stream_wait_close+0x1b0/0x1b0
     ? wait_woken+0xc0/0xc0
     ? tcp_current_mss+0xc5/0x110
     tcp_sendmsg_locked+0x634/0x15d0
     ? tcp_set_state+0x2e0/0x2e0
     ? __kasan_slab_free+0x1d1/0x230
     ? kmem_cache_free+0x70/0x140
     ? sk_psock_backlog+0x40c/0x4b0
     ? process_one_work+0x40b/0x660
     ? worker_thread+0x82/0x680
     ? kthread+0x1b9/0x1e0
     ? ret_from_fork+0x1f/0x30
     ? check_preempt_curr+0xaf/0x130
     ? iov_iter_kvec+0x5f/0x70
     ? kernel_sendmsg_locked+0xa0/0xe0
     skb_send_sock_locked+0x273/0x3c0
     ? skb_splice_bits+0x180/0x180
     ? start_thread+0xe0/0xe0
     ? update_min_vruntime.constprop.27+0x88/0xc0
     sk_psock_backlog+0xb3/0x4b0
     ? strscpy+0xbf/0x1e0
     process_one_work+0x40b/0x660
     worker_thread+0x82/0x680
     ? process_one_work+0x660/0x660
     kthread+0x1b9/0x1e0
     ? __kthread_create_on_node+0x250/0x250
     ret_from_fork+0x1f/0x30
    
    Fixes: 20bf50de ("skbuff: Function to send an skbuf on a socket")
    Reported-by: 's avatarJakub Sitnicki <jakub@cloudflare.com>
    Tested-by: 's avatarJakub Sitnicki <jakub@cloudflare.com>
    Signed-off-by: 's avatarJohn Fastabend <john.fastabend@gmail.com>
    Signed-off-by: 's avatarDaniel Borkmann <daniel@iogearbox.net>
    Signed-off-by: 's avatarSasha Levin <sashal@kernel.org>
    635e92cf
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