on 2022/4/21 16:01, Christian Brauner wrote:
> On Thu, Apr 21, 2022 at 03:54:15PM +0800, Yang Xu wrote:
>> This has no functional change. Just create and export inode_sgid_strip
>> api for the subsequent patch. This function is used to strip inode's
>> S_ISGID mode when init a new inode.
>>
>> Signed-off-by: Yang Xu<xuyang2018.jy@xxxxxxxxxxx>
>> ---
>
> Could you please add the kernel doc I sketched below to the new helper?
Great, will send a v6 patch for this and also add fixes tag and cc
statble kernel for " fs: Add missing umask strip in vfs_tmpfile" patch.
>
> Looks good to me,
> Reviewed-by: Christian Brauner (Microsoft)<brauner@xxxxxxxxxx>
thanks for your review.
>
>> v4-v5:
>> use umode_t return value instead of mode pointer
>> fs/inode.c | 23 +++++++++++++++++++----
>> include/linux/fs.h | 2 ++
>> 2 files changed, 21 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/inode.c b/fs/inode.c
>> index 9d9b422504d1..57130e4ef8b4 100644
>> --- a/fs/inode.c
>> +++ b/fs/inode.c
>> @@ -2246,10 +2246,8 @@ void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode,
>> /* Directories are special, and always inherit S_ISGID */
>> if (S_ISDIR(mode))
>> mode |= S_ISGID;
>> - else if ((mode& (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)&&
>> - !in_group_p(i_gid_into_mnt(mnt_userns, dir))&&
>> - !capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID))
>> - mode&= ~S_ISGID;
>> + else
>> + mode = inode_sgid_strip(mnt_userns, dir, mode);
>> } else
>> inode_fsgid_set(inode, mnt_userns);
>> inode->i_mode = mode;
>> @@ -2405,3 +2403,20 @@ struct timespec64 current_time(struct inode *inode)
>> return timestamp_truncate(now, inode);
>> }
>> EXPORT_SYMBOL(current_time);
>> +
>
> /**
> * inode_sgid_strip - handle the sgid bit for non-directories
> * @mnt_userns: idmapping of the mount
> * @dir: parent directory
> * @mode: mode of the file to be created in @dir
> *
> * If the @mode of the new file has both the S_ISGID and S_IXGRP bit
> * raised and @dir has the S_ISGID bit raised ensure that the caller is
> * either in the group of the parent directory or they have CAP_FSETID
> * in their user namespace and are privileged over the parent directory.
> * In all other cases, strip the S_ISGID bit from @mode.
> *
> * Return: the new mode to use for the file
> */
>> +umode_t inode_sgid_strip(struct user_namespace *mnt_userns,
>> + const struct inode *dir, umode_t mode)
>> +{
>> + if (S_ISDIR(mode) || !dir || !(dir->i_mode& S_ISGID))
>> + return mode;
>> + if ((mode& (S_ISGID | S_IXGRP)) != (S_ISGID | S_IXGRP))
>> + return mode;
>> + if (in_group_p(i_gid_into_mnt(mnt_userns, dir)))
>> + return mode;
>> + if (capable_wrt_inode_uidgid(mnt_userns, dir, CAP_FSETID))
>> + return mode;
>> +
>> + mode&= ~S_ISGID;
>> + return mode;
>> +}
>> +EXPORT_SYMBOL(inode_sgid_strip);
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index bbde95387a23..532de76c9b91 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -1897,6 +1897,8 @@ extern long compat_ptr_ioctl(struct file *file, unsigned int cmd,
>> void inode_init_owner(struct user_namespace *mnt_userns, struct inode *inode,
>> const struct inode *dir, umode_t mode);
>> extern bool may_open_dev(const struct path *path);
>> +umode_t inode_sgid_strip(struct user_namespace *mnt_userns,
>> + const struct inode *dir, umode_t mode);
>>
>> /*
>> * This is the "filldir" function type, used by readdir() to let
>> --
>> 2.27.0
>>
