[PATCH] fs/nilfs2: Integer overflow in nilfs_ioctl_wrap_copy()

[PATCH] fs/nilfs2: Integer overflow in nilfs_ioctl_wrap_copy()

[Wenliang Fan]

The local variable 'pos' comes from userspace. If a large number was
passed, there would be an integer overflow in the following line:
        pos += n;

Signed-off-by: Wenliang Fan <fanwlexca@gmail.com>
---
 fs/nilfs2/ioctl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index b44bdb2..a260a98 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -65,6 +65,8 @@ static int nilfs_ioctl_wrap_copy(struct the_nilfs *nilfs,
 	ret = 0;
 	total = 0;
 	pos = argv->v_index;
+	if (pos > ULONG_MAX - argv->v_nmembs)
+		return -EINVAL;
 	for (i = 0; i < argv->v_nmembs; i += n) {
 		n = (argv->v_nmembs - i < maxmembs) ?
 			argv->v_nmembs - i : maxmembs;
-- 
1.8.5.rc1.28.g7061504

Re: [PATCH] fs/nilfs2: Integer overflow in nilfs_ioctl_wrap_copy()

[Vyacheslav Dubeyko]

Hi,

On Sat, 2013-12-28 at 10:28 +0800, Wenliang Fan wrote:
> The local variable 'pos' comes from userspace. If a large number was
> passed, there would be an integer overflow in the following line:
>         pos += n;
> 
> Signed-off-by: Wenliang Fan <fanwlexca@gmail.com>
> ---
>  fs/nilfs2/ioctl.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
> index b44bdb2..a260a98 100644
> --- a/fs/nilfs2/ioctl.c
> +++ b/fs/nilfs2/ioctl.c
> @@ -65,6 +65,8 @@ static int nilfs_ioctl_wrap_copy(struct the_nilfs *nilfs,
>  	ret = 0;
>  	total = 0;
>  	pos = argv->v_index;
> +	if (pos > ULONG_MAX - argv->v_nmembs)
> +		return -EINVAL;

I am slightly confused. Does this patch means that you refused previous
one? Or this patch is addition to the previous one?

You need to prepare next version of the patch or to prepare patch set
from two patches. And it makes sense to provide changelog of your work,
I think.

Thanks,
Vyacheslav Dubeyko.

>  	for (i = 0; i < argv->v_nmembs; i += n) {
>  		n = (argv->v_nmembs - i < maxmembs) ?
>  			argv->v_nmembs - i : maxmembs;

[PATCH] fs/nilfs2: Integer overflow in nilfs_ioctl_wrap_copy()

[Wenliang Fan]

The local variable 'pos' comes from userspace. If a large number was
passed, there would be an integer overflow in the following line:
	pos += n;

Signed-off-by: Wenliang Fan <fanwlexca@gmail.com>
---
 fs/nilfs2/ioctl.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index b44bdb2..b2bac9a 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -90,8 +90,13 @@ static int nilfs_ioctl_wrap_copy(struct the_nilfs *nilfs,
 		total += nr;
 		if ((size_t)nr < n)
 			break;
-		if (pos == ppos)
+		if (pos == ppos) {
+			if (pos > ULONG_MAX - n) {
+				ret = -EINVAL;
+				break;
+			}
 			pos += n;
+		}
 	}
 	argv->v_nmembs = total;
 
-- 
1.8.5.rc1.28.g7061504

Re: [PATCH] fs/nilfs2: Integer overflow in nilfs_ioctl_wrap_copy()

[Vyacheslav Dubeyko]

On Fri, 2013-12-20 at 15:46 +0800, Wenliang Fan wrote:
> The local variable 'pos' comes from userspace. If a large number was
> passed, there would be an integer overflow in the following line:
> 	pos += n;
> 

What about check before enter into the cycle? If you are talking about
possible huge number then you can receive huge number from userspace
before entering in the cycle.

Thanks,
Vyacheslav Dubeyko.

> Signed-off-by: Wenliang Fan <fanwlexca@gmail.com>
> ---
>  fs/nilfs2/ioctl.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
> index b44bdb2..b2bac9a 100644
> --- a/fs/nilfs2/ioctl.c
> +++ b/fs/nilfs2/ioctl.c
> @@ -90,8 +90,13 @@ static int nilfs_ioctl_wrap_copy(struct the_nilfs *nilfs,
>  		total += nr;
>  		if ((size_t)nr < n)
>  			break;
> -		if (pos == ppos)
> +		if (pos == ppos) {
> +			if (pos > ULONG_MAX - n) {
> +				ret = -EINVAL;
> +				break;
> +			}
>  			pos += n;
> +		}
>  	}
>  	argv->v_nmembs = total;
>