libceph: validate con->state at the top of try_write()
ceph_con_workfn() validates con->state before calling try_read() and then try_write(). However, try_read() temporarily releases con->mutex, notably in process_message() and ceph_con_in_msg_alloc(), opening the window for ceph_con_close() to sneak in, close the connection and release con->sock. When try_write() is called on the assumption that con->state is still valid (i.e. not STANDBY or CLOSED), a NULL sock gets passed to the networking stack: BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 IP: selinux_socket_sendmsg+0x5/0x20 Make sure con->state is valid at the top of try_write() and add an explicit BUG_ON for this, similar to try_read(). Cc: stable@vger.kernel.org Link: https://tracker.ceph.com/issues/23706 Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Reviewed-by: Jason Dillaman <dillaman@redhat.com>
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@ -2569,6 +2569,11 @@ static int try_write(struct ceph_connection *con)
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int ret = 1;
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dout("try_write start %p state %lu\n", con, con->state);
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if (con->state != CON_STATE_PREOPEN &&
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con->state != CON_STATE_CONNECTING &&
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con->state != CON_STATE_NEGOTIATING &&
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con->state != CON_STATE_OPEN)
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return 0;
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more:
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dout("try_write out_kvec_bytes %d\n", con->out_kvec_bytes);
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@ -2594,6 +2599,8 @@ more:
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}
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more_kvec:
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BUG_ON(!con->sock);
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/* kvec data queued? */
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if (con->out_kvec_left) {
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ret = write_partial_kvec(con);
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