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]>
---
fs/libfs.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/libfs.c b/fs/libfs.c
index fc34361..2dcf40e 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, &val);
+ if (ret)
+ goto out;
ret = attr->set(attr->data, val);
if (ret == 0)
ret = len; /* on success, claim we got the whole input */
--
2.8.1
On Tue, 10 Nov 2020 17:25:24 +0800 Yicong Yang <[email protected]> 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'?
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 <[email protected]> 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
> .
>
On Wed, 11 Nov 2020 18:18:31 +0800 Yicong Yang <[email protected]> wrote:
> 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 <[email protected]> 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.
Sure. But the compiler will convert an unsigned long long into a u64
quite happily, regardless of how u64 was actually implemented.
However the compiler will not convert a `u64 *' into an `unsigned long
long *' if the underlying type of u64 happens to be `unsigned long'.
It will warn.