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| author | Dexuan Cui <decui@microsoft.com> | 2019-07-31 01:25:45 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-09-16 08:20:45 +0200 |
| commit | dd17277c2483db588c470df406f63059f3975432 (patch) | |
| tree | 98d2412b38b086126c289b780e3e2e32bc667fb5 /net | |
| parent | 28400323ea2e541b22666dfd62b6836bc97d629b (diff) | |
| download | linux-stable-dd17277c2483db588c470df406f63059f3975432.tar.gz linux-stable-dd17277c2483db588c470df406f63059f3975432.tar.bz2 linux-stable-dd17277c2483db588c470df406f63059f3975432.zip | |
hv_sock: Fix hang when a connection is closed
[ Upstream commit 685703b497bacea8765bb409d6b73455b73c540e ]
There is a race condition for an established connection that is being closed
by the guest: the refcnt is 4 at the end of hvs_release() (Note: here the
'remove_sock' is false):
1 for the initial value;
1 for the sk being in the bound list;
1 for the sk being in the connected list;
1 for the delayed close_work.
After hvs_release() finishes, __vsock_release() -> sock_put(sk) *may*
decrease the refcnt to 3.
Concurrently, hvs_close_connection() runs in another thread:
calls vsock_remove_sock() to decrease the refcnt by 2;
call sock_put() to decrease the refcnt to 0, and free the sk;
next, the "release_sock(sk)" may hang due to use-after-free.
In the above, after hvs_release() finishes, if hvs_close_connection() runs
faster than "__vsock_release() -> sock_put(sk)", then there is not any issue,
because at the beginning of hvs_close_connection(), the refcnt is still 4.
The issue can be resolved if an extra reference is taken when the
connection is established.
Fixes: a9eeb998c28d ("hv_sock: Add support for delayed close")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'net')
| -rw-r--r-- | net/vmw_vsock/hyperv_transport.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c index 52ac3e49c7ef..ec72a5edaa1b 100644 --- a/net/vmw_vsock/hyperv_transport.c +++ b/net/vmw_vsock/hyperv_transport.c @@ -320,6 +320,11 @@ static void hvs_close_connection(struct vmbus_channel *chan) lock_sock(sk); hvs_do_close_lock_held(vsock_sk(sk), true); release_sock(sk); + + /* Release the refcnt for the channel that's opened in + * hvs_open_connection(). + */ + sock_put(sk); } static void hvs_open_connection(struct vmbus_channel *chan) @@ -389,6 +394,9 @@ static void hvs_open_connection(struct vmbus_channel *chan) } set_per_channel_state(chan, conn_from_host ? new : sk); + + /* This reference will be dropped by hvs_close_connection(). */ + sock_hold(conn_from_host ? new : sk); vmbus_set_chn_rescind_callback(chan, hvs_close_connection); /* Set the pending send size to max packet size to always get |