On Sun, 2016-07-10 at 17:07 +0900, Tomohiro Kusumi wrote:
> According to include/uapi/linux/auto_fs.h, include/uapi/linux/auto_fs4.h,
> and include/linux/auto_dev-ioctl.h, nr part of
> AUTOFS_IOC_XXX starts off from 0x60 and
> AUTOFS_DEV_IOCTL_XXX starts off from 0x71 which is 0x60+0x11.
>
> From the way above macros are defined, it seems
> AUTOFS_DEV_IOCTL_IOC_COUNT should be (0x20-0x11) instead of (0x20-11).
> (Otherwise it's hard to figure out where 11 comes from)
You're correct, this is wrong but I think this change is also wrong.
And so is the range check in dev-ioctl.c.
There's no check for an ioctl number greater than the range claimed by autofs
and the check in dev-ioctl.c seeks to check the number used is within the range
used by the dev ioctls.
Essentially
AUTOFS_DEV_IOCTL_VERSION_CMD - AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD = 0xd
14 ioctls ranging from 0x71 - 0x7e (inclusive).
The range check in dev-ioctl.c is:
if (_IOC_TYPE(command) != _IOC_TYPE(AUTOFS_DEV_IOCTL_IOC_FIRST) ||
cmd - cmd_first >= AUTOFS_DEV_IOCTL_IOC_COUNT) {
return -ENOTTY;
}
so I think AUTOFS_DEV_IOCTL_IOC_COUNT should be:
#define AUTOFS_DEV_IOCTL_IOC_COUNT \
(AUTOFS_DEV_IOCTL_VERSION_CMD - AUTOFS_DEV_IOCTL_ISMOUNTPOINT_CMD)
and the check should be:
if (_IOC_TYPE(command) != _IOC_TYPE(AUTOFS_DEV_IOCTL_IOC_FIRST) ||
cmd_first - cmd >= AUTOFS_DEV_IOCTL_IOC_COUNT) {
return
-ENOTTY;
}
What do you think?
>
> COUNT macros are being used to test distance of an ioctl command
> in question from the smallest one, so we don't want it to be
> larger than necessary.
>
> Signed-off-by: Tomohiro Kusumi <kusumi.tomohiro@xxxxxxxxx>
> ---
> fs/autofs4/autofs_i.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
> index 73e3d38..7ef4d08 100644
> --- a/fs/autofs4/autofs_i.h
> +++ b/fs/autofs4/autofs_i.h
> @@ -20,7 +20,7 @@
> #define AUTOFS_IOC_COUNT 32
>
> #define AUTOFS_DEV_IOCTL_IOC_FIRST (AUTOFS_DEV_IOCTL_VERSION)
> -#define AUTOFS_DEV_IOCTL_IOC_COUNT (AUTOFS_IOC_COUNT - 11)
> +#define AUTOFS_DEV_IOCTL_IOC_COUNT (AUTOFS_IOC_COUNT - 0x11)
>
> #include <linux/kernel.h>
> #include <linux/slab.h>
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