Re: [PATCH 1/2] fs: Add and export file_needs_remove_privs

[Bernd Schubert <bernd.schubert@fastmail.fm>]

On 8/31/23 15:40, Christian Brauner wrote:
> 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@szeredi.hu>
>> Cc: Dharmendra Singh <dsingh@ddn.com>
>> Cc: Josef Bacik <josef@toxicpanda.com>
>> Cc: linux-btrfs@vger.kernel.org
>> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
>> Cc: Christian Brauner <brauner@kernel.org>
>> Cc: linux-fsdevel@vger.kernel.org
>> Signed-off-by: Bernd Schubert <bschubert@ddn.com>
>> ---
>>   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...

Is there anything specific you are suggesting?

And thanks for typo/grammar annotations, I'm going to wait for btrfs 
feedback before I'm going to send a new version.


Thanks,
Bernd