On Tue, 10 Nov 2020 17:25:24 +0800 Yicong Yang <yangyicong@xxxxxxxxxxxxx> 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. > > ... > > --- 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, &val); > + if (ret) > + goto out; > ret = attr->set(attr->data, val); > if (ret == 0) > ret = len; /* on success, claim we got the whole input */ kstrtoull() takes an `unsigned long long *', but `val' is a u64. I think this probably works OK on all architectures (ie, no 64-bit architectures are using `unsigned long' for u64). But perhaps `val' should have type `unsigned long long'?
