On Fri, Nov 13, 2020 at 05:56:09PM +0800, Yicong Yang wrote:
> The attr->set() receive a value of u64, but simple_strtoll() is used
> for doing the conversion. It will lead to the error cast if user inputs
> a negative value.
>
> Use kstrtoull() instead of simple_strtoll() to convert a string got
> from the user to an unsigned value. The former will return '-EINVAL' if
> it gets a negetive value, but the latter can't handle the situation
> correctly.
>
> Fixes: f7b88631a897 ("fs/libfs.c: fix simple_attr_write() on 32bit machines")
> Signed-off-by: Yicong Yang <[email protected]>
> ---
> Change since v1:
> - address the compile warning for non-64 bit platform
>
> fs/libfs.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/libfs.c b/fs/libfs.c
> index fc34361..3a0d99c 100644
> --- a/fs/libfs.c
> +++ b/fs/libfs.c
> @@ -977,7 +977,9 @@ ssize_t simple_attr_write(struct file *file, const char
> __user *buf,
> goto out;
>
> attr->set_buf[size] = '\0';
> - val = simple_strtoll(attr->set_buf, NULL, 0);
> + ret = kstrtoull(attr->set_buf, 0, (unsigned long long *)&val);
> + if (ret)
> + goto out;
> ret = attr->set(attr->data, val);
> if (ret == 0)
> ret = len; /* on success, claim we got the whole input */
Make val unsigned long long instead.
