On Thu, Aug 31, 2023 at 01:24:30PM +0200, Bernd Schubert wrote:
> File systems want to hold a shared lock for DIO writes,
> but may need to drop file priveliges - that a requires an
> exclusive lock. The new export function file_needs_remove_privs()
> is added in order to first check if that is needed.
>
> Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
> Cc: Dharmendra Singh <dsingh@xxxxxxx>
> Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
> Cc: linux-btrfs@xxxxxxxxxxxxxxx
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
> Signed-off-by: Bernd Schubert <bschubert@xxxxxxx>
> ---
> fs/inode.c | 8 ++++++++
> include/linux/fs.h | 1 +
> 2 files changed, 9 insertions(+)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index 67611a360031..9b05db602e41 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -2013,6 +2013,14 @@ int dentry_needs_remove_privs(struct mnt_idmap *idmap,
> return mask;
> }
>
> +int file_needs_remove_privs(struct file *file)
> +{
> + struct dentry *dentry = file_dentry(file);
> +
> + return dentry_needs_remove_privs(file_mnt_idmap(file), dentry);
Ugh, I wanted to propose to get rid of this dentry dance but I propsed
that before and remembered it's because of __vfs_getxattr() which is
called from the capability security hook that we need it...
