Hi, Thanks for reviewing this. On 2020/11/11 3:18, Andrew Morton wrote: > 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'? the attr->set() takes 'val' as u64, so maybe we can stay it unchanged here if it works well. Thanks, Yicong > . >
