on 2022/4/14 20:02, Christian Brauner wrote:
> On Thu, Apr 14, 2022 at 03:57:17PM +0800, Yang Xu wrote:
>> inode_sgid_strip() function is used to strip S_ISGID mode
>> when creat/open/mknod file.
>>
>> Reviewed-by: Christian Brauner (Microsoft)<brauner@xxxxxxxxxx>
>> Signed-off-by: Yang Xu<xuyang2018.jy@xxxxxxxxxxx>
>> ---
>> fs/inode.c | 18 ++++++++++++++++++
>> include/linux/fs.h | 3 ++-
>> 2 files changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/inode.c b/fs/inode.c
>> index 9d9b422504d1..d63264998855 100644
>> --- a/fs/inode.c
>> +++ b/fs/inode.c
>> @@ -2405,3 +2405,21 @@ struct timespec64 current_time(struct inode *inode)
>> return timestamp_truncate(now, inode);
>> }
>> EXPORT_SYMBOL(current_time);
>> +
>> +void inode_sgid_strip(struct user_namespace *mnt_userns, struct inode *dir,
>> + umode_t *mode)
>> +{
>> + if (!dir || !(dir->i_mode& S_ISGID))
>> + return;
>> + if ((*mode& (S_ISGID | S_IXGRP)) != (S_ISGID | S_IXGRP))
>> + return;
>> + if (S_ISDIR(*mode))
>> + return;
>> + if (in_group_p(i_gid_into_mnt(mnt_userns, dir)))
>> + return;
>> + if (capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID))
>> + return;
>> +
>> + *mode&= ~S_ISGID;
>> +}
>> +EXPORT_SYMBOL(inode_sgid_strip);
>
>
> I still think this should return umode_t with the setgid bit stripped
> instead of modifying the mode directly. I may have misunderstood Dave,
> but I thought he preferred to return umode_t too?
Dave's comment as below:
"
Agreed, that's a much nicer API for this function - it makes it
clear that it can modifying the mode that is passed in.
"
So I think Dave should like modify mode directly instead of returning a
umode_t value.
@Dave So which way do you mean?
Best Regards
Yang Xu
>
> umode_t inode_sgid_strip(struct user_namespace *mnt_userns, struct inode *dir, umode_t mode)
> {
> if (S_ISDIR(mode))
> return mode;
>
> if (!dir || !(dir->i_mode& S_ISGID))
> return;
>
> if ((mode& (S_ISGID | S_IXGRP)) != (S_ISGID | S_IXGRP))
> return;
>
> if (in_group_p(i_gid_into_mnt(mnt_userns, dir)))
> return;
>
> if (capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID))
> return;
>
> return mode& ~S_ISGID;
> }
