UbiquitousOS
/
OpenCloudOS-Kernel
mirror of https://gitee.com/OpenCloudOS/OpenCloudOS-Kernel.git
11
0
Fork 0
Code Issues Projects Releases Wiki Activity

greybus: uart-gb: improve minor device number error checking 

When alloc_minor() finds an available minor device number it
does not constrain the highest number desired.  Instead, it
relies on its caller, tty_gb_probe() to see if the returned
number indicates all minor numbers have been exhausted.

There are a couple problems with this--or rather with this
code.

First, if an allocation is attempted *after* GB_NUM_MINORS
is returned, a new number greater than (but not equal to)
GB_NUM_MINORS will be allocated, and that won't produce
any error condition.

Second, alloc_minor() can return an error code (like -ENOMEM).  And
its caller is only checking for GB_NUM_MINORS.  If an error code
is returned, tty_gb_probe() simply uses it.

Change alloc_minor() so it requests minor device numbers in the
range 0..(GB_NUM_MINORS-1), and use an error return to detect
when the minor device numbers have been exhausted.

If alloc_minor() returns -ENOSPC (from idr_alloc()), translate that
to -ENODEV.  The only other error we might see is -ENOMEM, and if
we get that, return it.

Finally, zero gb_tty->minor when it's released.  (If this is
actually important a reserved value like GB_NUM_MINORS should
be used instead to signify a gb_tty with no minor assigned.)

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alex Elder 2014-08-18 18:25:11 -05:00 committed by Greg Kroah-Hartman
parent e68453ed28
commit ff5f0b3822
1 changed files with 13 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
drivers/staging/greybus/uart-gb.c
View File

@ -80,19 +80,20 @@ static int alloc_minor(struct gb_tty *gb_tty)
int minor;
mutex_lock(&table_lock);
minor = idr_alloc(&tty_minors, gb_tty, 0, 0, GFP_KERNEL);
if (minor < 0)
goto error;
gb_tty->minor = minor;
error:
minor = idr_alloc(&tty_minors, gb_tty, 0, GB_NUM_MINORS, GFP_KERNEL);
mutex_unlock(&table_lock);
if (minor >= 0)
gb_tty->minor = minor;
return minor;
}
static void release_minor(struct gb_tty *gb_tty)
{
int minor = gb_tty->minor;
gb_tty->minor = 0; /* Maybe should use an invalid value instead */
mutex_lock(&table_lock);
idr_remove(&tty_minors, gb_tty->minor);
idr_remove(&tty_minors, minor);
mutex_unlock(&table_lock);
}
@ -400,9 +401,12 @@ static int tty_gb_probe(struct greybus_device *gdev, const struct greybus_device
return -ENOMEM;
minor = alloc_minor(gb_tty);
if (minor == GB_NUM_MINORS) {
dev_err(&gdev->dev, "no more free minor numbers\n");
return -ENODEV;
if (minor < 0) {
if (minor == -ENOSPC) {
dev_err(&gdev->dev, "no more free minor numbers\n");
return -ENODEV;
}
return minor;
}
gb_tty->minor = minor;