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mei: remove support for broken parallel read

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Parallel reads from multiple threads on a file descriptor
are not well defined and racy. It is safer to return to original
behavior and simply fail the additional read.
The solution is to remove request for next read credit.

Cc: <stable@vger.kernel.org> #4.9
Fixes: ff1586a7ea ("mei: enqueue consecutive reads")
Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alexander Usyskin 2017-02-08 00:41:45 +02:00 committed by Greg Kroah-Hartman
parent dd37eed7db
commit cb97fbbcac
1 changed files with 26 additions and 22 deletions
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48
drivers/misc/mei/main.c
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@ -182,32 +182,36 @@ static ssize_t mei_read(struct file *file, char __user *ubuf,
goto out;
}
if (rets == -EBUSY &&
!mei_cl_enqueue_ctrl_wr_cb(cl, length, MEI_FOP_READ, file)) {
rets = -ENOMEM;
again:
mutex_unlock(&dev->device_lock);
if (wait_event_interruptible(cl->rx_wait,
!list_empty(&cl->rd_completed) ||
!mei_cl_is_connected(cl))) {
if (signal_pending(current))
return -EINTR;
return -ERESTARTSYS;
}
mutex_lock(&dev->device_lock);
if (!mei_cl_is_connected(cl)) {
rets = -ENODEV;
goto out;
}
do {
mutex_unlock(&dev->device_lock);
cb = mei_cl_read_cb(cl, file);
if (!cb) {
/*
* For amthif all the waiters are woken up,
* but only fp with matching cb->fp get the cb,
* the others have to return to wait on read.
*/
if (cl == &dev->iamthif_cl)
goto again;
if (wait_event_interruptible(cl->rx_wait,
(!list_empty(&cl->rd_completed)) ||
(!mei_cl_is_connected(cl)))) {
if (signal_pending(current))
return -EINTR;
return -ERESTARTSYS;
}
mutex_lock(&dev->device_lock);
if (!mei_cl_is_connected(cl)) {
rets = -ENODEV;
goto out;
}
cb = mei_cl_read_cb(cl, file);
} while (!cb);
rets = 0;
goto out;
}
copy_buffer:
/* now copy the data to user space */