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The crash is observed when a service is being disabled host side while
userspace daemon is connected to the device:
[ 90.244859] general protection fault: 0000 [#1] SMP
...
[ 90.800082] Call Trace:
[ 90.800082] [<ffffffff81187008>] __fput+0xc8/0x1f0
[ 90.800082] [<ffffffff8118716e>] ____fput+0xe/0x10
...
[ 90.800082] [<ffffffff81015278>] do_signal+0x28/0x580
[ 90.800082] [<ffffffff81086656>] ? finish_task_switch+0xa6/0x180
[ 90.800082] [<ffffffff81443ebf>] ? __schedule+0x28f/0x870
[ 90.800082] [<ffffffffa01ebbaa>] ? hvt_op_read+0x12a/0x140 [hv_utils]
...
The problem is that hvutil_transport_destroy() which does misc_deregister()
freeing the appropriate device is reachable by two paths: module unload
and from util_remove(). While module unload path is protected by .owner in
struct file_operations util_remove() path is not. Freeing the device while
someone holds an open fd for it is a show stopper.
In general, it is not possible to revoke an fd from all users so the only
way to solve the issue is to defer freeing the hvutil_transport structure.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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When Hyper-V host asks us to remove some util driver by closing the
appropriate channel there is no easy way to force the current file
descriptor holder to hang up but we can start to respond -EBADF to all
operations asking it to exit gracefully.
As we're setting hvt->mode from two separate contexts now we need to use
a proper locking.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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As a preparation to reusing outmsg_lock to protect test-and-set openrations
on 'mode' rename it the more general 'lock'.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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inmsg should be freed in case of on_msg() failure to avoid memory leak.
Preserve the error code from on_msg().
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Use memdup_user to handle OOM.
Fixes: 14b50f80c32d ('Drivers: hv: util: introduce hv_utils_transport abstraction')
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Catch allocation errors in hvutil_transport_send.
Fixes: 14b50f80c32d ('Drivers: hv: util: introduce hv_utils_transport abstraction')
Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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We don't catch this allocation failure because there is a typo and we
check the wrong variable.
Fixes: 14b50f80c32d ('Drivers: hv: util: introduce hv_utils_transport abstraction')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The intention is to make KVP/VSS drivers work through misc char devices.
Introduce an abstraction for kernel/userspace communication to make the
migration smoother. Transport operational mode (netlink or char device)
is determined by the first received message. To support driver upgrades
the switch from netlink to chardev operational mode is supported.
Every hv_util daemon is supposed to register 2 callbacks:
1) on_msg() to get notified when the userspace daemon sent a message;
2) on_reset() to get notified when the userspace daemon drops the connection.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Tested-by: Alex Ng <alexng@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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