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gpiolib: cdev: Cleanup kfifo_out() error handling

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The handling of kfifo_out() errors in read functions obscures any error.
The error condition should never occur but, while a ret is set to -EIO, it
is subsequently ignored and the read functions instead return the number
of bytes copied to that point, potentially masking the fact that any error
occurred.

Log a warning and return -EIO in the case of a kfifo_out() error to make
it clear something very odd is going on here.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Link: https://lore.kernel.org/r/20240529131953.195777-4-warthog618@gmail.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
This commit is contained in:
Kent Gibson 2024-05-29 21:19:53 +08:00 committed by Bartosz Golaszewski
parent 4ce5ca654a
commit 2ba4746b41
1 changed files with 27 additions and 26 deletions
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53
drivers/gpio/gpiolib-cdev.c
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@ -1642,16 +1642,15 @@ static ssize_t linereq_read(struct file *file, char __user *buf,
return ret;
}
ret = kfifo_out(&lr->events, &le, 1);
}
if (ret != 1) {
/*
* This should never happen - we were holding the
* lock from the moment we learned the fifo is no
* longer empty until now.
*/
ret = -EIO;
break;
if (kfifo_out(&lr->events, &le, 1) != 1) {
/*
* This should never happen - we hold the
* lock from the moment we learned the fifo
* is no longer empty until now.
*/
WARN(1, "failed to read from non-empty kfifo");
return -EIO;
}
}
if (copy_to_user(buf + bytes_read, &le, sizeof(le)))
@ -1995,16 +1994,15 @@ static ssize_t lineevent_read(struct file *file, char __user *buf,
return ret;
}
ret = kfifo_out(&le->events, &ge, 1);
}
if (ret != 1) {
/*
* This should never happen - we were holding the lock
* from the moment we learned the fifo is no longer
* empty until now.
*/
ret = -EIO;
break;
if (kfifo_out(&le->events, &ge, 1) != 1) {
/*
* This should never happen - we hold the
* lock from the moment we learned the fifo
* is no longer empty until now.
*/
WARN(1, "failed to read from non-empty kfifo");
return -EIO;
}
}
if (copy_to_user(buf + bytes_read, &ge, ge_size))
@ -2707,12 +2705,15 @@ static ssize_t lineinfo_watch_read(struct file *file, char __user *buf,
if (count < event_size)
return -EINVAL;
#endif
ret = kfifo_out(&cdev->events, &event, 1);
}
if (ret != 1) {
ret = -EIO;
break;
/* We should never get here. See lineevent_read(). */
if (kfifo_out(&cdev->events, &event, 1) != 1) {
/*
* This should never happen - we hold the
* lock from the moment we learned the fifo
* is no longer empty until now.
*/
WARN(1, "failed to read from non-empty kfifo");
return -EIO;
}
}
#ifdef CONFIG_GPIO_CDEV_V1