[PATCH v2] fs/nilfs2: use standard array-copy-function

[PATCH v2] fs/nilfs2: use standard array-copy-function

[Philipp Stanner]

ioctl.c utilizes memdup_user() to copy a userspace array. An overflow
check is performed manually before the function's invocation.

The new function memdup_array_user() standardizes copying userspace
arrays, thus, improving readability by making it more clear that an
array is being copied. Additionally, it also performs an overflow check.

Remove the (now redundant) manual overflow-check and replace
memdup_user() with memdup_array_user().

In addition, improve the grammar of the comment above
memdup_array_user().

Suggested-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Philipp Stanner <pstanner@redhat.com>
---
Changes in v2:
- Rename + rephrase commit so that it's clear that this is a
  cleanup-patch.
- Mention the grammar improvement of the comment in the commit message.
- Remove the preceding manual overflow-check, since that is now
  redundant.
---
 fs/nilfs2/ioctl.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 40ffade49f38..cfb6aca5ec38 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -872,16 +872,14 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
 	nsegs = argv[4].v_nmembs;
 	if (argv[4].v_size != argsz[4])
 		goto out;
-	if (nsegs > UINT_MAX / sizeof(__u64))
-		goto out;
 
 	/*
 	 * argv[4] points to segment numbers this ioctl cleans.  We
-	 * use kmalloc() for its buffer because memory used for the
-	 * segment numbers is enough small.
+	 * use kmalloc() for its buffer because the memory used for the
+	 * segment numbers is small enough.
 	 */
-	kbufs[4] = memdup_user((void __user *)(unsigned long)argv[4].v_base,
-			       nsegs * sizeof(__u64));
+	kbufs[4] = memdup_array_user((void __user *)(unsigned long)argv[4].v_base,
+				     nsegs, sizeof(__u64));
 	if (IS_ERR(kbufs[4])) {
 		ret = PTR_ERR(kbufs[4]);
 		goto out;
-- 
2.41.0

Re: [PATCH v2] fs/nilfs2: use standard array-copy-function

[Ryusuke Konishi]

On Sat, Nov 4, 2023 at 3:49 AM Philipp Stanner wrote:
>
> ioctl.c utilizes memdup_user() to copy a userspace array. An overflow
> check is performed manually before the function's invocation.
>
> The new function memdup_array_user() standardizes copying userspace
> arrays, thus, improving readability by making it more clear that an
> array is being copied. Additionally, it also performs an overflow check.
>
> Remove the (now redundant) manual overflow-check and replace
> memdup_user() with memdup_array_user().
>
> In addition, improve the grammar of the comment above
> memdup_array_user().
>
> Suggested-by: Dave Airlie <airlied@redhat.com>
> Signed-off-by: Philipp Stanner <pstanner@redhat.com>
> ---
> Changes in v2:
> - Rename + rephrase commit so that it's clear that this is a
>   cleanup-patch.
> - Mention the grammar improvement of the comment in the commit message.
> - Remove the preceding manual overflow-check, since that is now
>   redundant.
> ---
>  fs/nilfs2/ioctl.c | 10 ++++------
>  1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
> index 40ffade49f38..cfb6aca5ec38 100644
> --- a/fs/nilfs2/ioctl.c
> +++ b/fs/nilfs2/ioctl.c
> @@ -872,16 +872,14 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
>         nsegs = argv[4].v_nmembs;
>         if (argv[4].v_size != argsz[4])
>                 goto out;
> -       if (nsegs > UINT_MAX / sizeof(__u64))
> -               goto out;
>
>         /*
>          * argv[4] points to segment numbers this ioctl cleans.  We
> -        * use kmalloc() for its buffer because memory used for the
> -        * segment numbers is enough small.
> +        * use kmalloc() for its buffer because the memory used for the
> +        * segment numbers is small enough.
>          */
> -       kbufs[4] = memdup_user((void __user *)(unsigned long)argv[4].v_base,
> -                              nsegs * sizeof(__u64));
> +       kbufs[4] = memdup_array_user((void __user *)(unsigned long)argv[4].v_base,
> +                                    nsegs, sizeof(__u64));
>         if (IS_ERR(kbufs[4])) {
>                 ret = PTR_ERR(kbufs[4]);
>                 goto out;
> --
> 2.41.0
>

Looks good.  Also, thank you for your detailed changelog.
As mentioned earlier, I will handle this for the next cycle.

Thanks,
Ryusuke Konishi