2020-06-16 01:59:29

by Waiman Long

Subject: [PATCH v4 3/3] btrfs: Use kfree() in btrfs_ioctl_get_subvol_info()

In btrfs_ioctl_get_subvol_info(), there is a classic case where kzalloc()
was incorrectly paired with kzfree(). According to David Sterba, there
isn't any sensitive information in the subvol_info that needs to be
cleared before freeing. So kfree_sensitive() isn't really needed,
use kfree() instead.

Reported-by: David Sterba <[email protected]>
Signed-off-by: Waiman Long <[email protected]>
---
fs/btrfs/ioctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f1dd9e4271e9..e8f7c5f00894 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2692,7 +2692,7 @@ static int btrfs_ioctl_get_subvol_info(struct file *file, void __user *argp)
btrfs_put_root(root);
out_free:
btrfs_free_path(path);
- kfree_sensitive(subvol_info);
+ kfree(subvol_info);
return ret;
}

--
2.18.1

2020-06-16 14:49:04

by David Sterba

Subject: Re: [PATCH v4 3/3] btrfs: Use kfree() in btrfs_ioctl_get_subvol_info()

On Mon, Jun 15, 2020 at 09:57:18PM -0400, Waiman Long wrote:
> In btrfs_ioctl_get_subvol_info(), there is a classic case where kzalloc()
> was incorrectly paired with kzfree(). According to David Sterba, there
> isn't any sensitive information in the subvol_info that needs to be
> cleared before freeing. So kfree_sensitive() isn't really needed,
> use kfree() instead.
>
> Reported-by: David Sterba <[email protected]>
> Signed-off-by: Waiman Long <[email protected]>
> ---
> fs/btrfs/ioctl.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index f1dd9e4271e9..e8f7c5f00894 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -2692,7 +2692,7 @@ static int btrfs_ioctl_get_subvol_info(struct file *file, void __user *argp)
> btrfs_put_root(root);
> out_free:
> btrfs_free_path(path);
> - kfree_sensitive(subvol_info);
> + kfree(subvol_info);

I would rather merge a patch doing to kzfree -> kfree instead of doing
the middle step to switch it to kfree_sensitive. If it would help
integration of your patchset I can push it to the next rc so there are
no kzfree left in the btrfs code. Treewide change like that can take
time so it would be one less problem to care about for you.