On Tue, 28 Oct 2008 10:14:30 +0900 Ian Kent <raven@xxxxxxxxxx> wrote:
> In a previous patch a comment was made that checking for the existence of
> a NULL terminator in strings copied from userspace wasn't needed as this
> is done in many places in the kernel without problem. This patch removes
> this string terminator check.
>
ah, OK. Now I'm worried.
>
> fs/autofs4/dev-ioctl.c | 20 --------------------
> 1 files changed, 0 insertions(+), 20 deletions(-)
>
> diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
> index 625abf5..304c1ff 100644
> --- a/fs/autofs4/dev-ioctl.c
> +++ b/fs/autofs4/dev-ioctl.c
> @@ -51,18 +51,6 @@ static int check_name(const char *name)
> }
>
> /*
> - * Check a string doesn't overrun the chunk of
> - * memory we copied from user land.
> - */
> -static int invalid_str(char *str, void *end)
> -{
> - while ((void *) str <= end)
> - if (!*str++)
> - return 0;
> - return -EINVAL;
> -}
> -
> -/*
> * Check that the user compiled against correct version of autofs
> * misc device code.
> *
> @@ -143,14 +131,6 @@ static int validate_dev_ioctl(int cmd, struct autofs_dev_ioctl *param)
> cmd);
> goto out;
> }
> -
> - err = invalid_str(param->path,
> - (void *) ((size_t) param + param->size));
> - if (err) {
> - AUTOFS_WARN("invalid path supplied for cmd(0x%08x)",
> - cmd);
> - goto out;
> - }
> }
>
> err = 0;
What will now happen if userspace passes in a non-null-terminated
string (if that's possible)?
Presumably that isn't possible, or it's never been tested, because
before we check for null-termination we run check_name(), which
_assumes_ null-termination!
The comment over validate_dev_ioctl() will need the "and is terminated"
removed after this change, yes?
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