Re: [PATCH 1/2] fs: add inode helpers for fsuid and fsgid

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James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> writes:

> On Tue, 2017-02-14 at 20:46 +1300, Eric W. Biederman wrote:
>> James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> writes:
>> 
>> > Now that we have two different views of filesystem ids (the 
>> > filesystem view and the kernel view), we have a problem in that
>> > current_fsuid/fsgid() return the kernel view but are sometimes used 
>> > in filesystem code where the filesystem view shoud be used.  This
>> > patch introduces helpers to produce the filesystem view of current 
>> > fsuid and fsgid.
>> 
>> If I am reading this right what we are seeing is that xfs explicitly
>> opted out of type safety with predictable results.   Accidentally
>> confusing kuids and uids, which is potentially security issue.
>> 
>> All of that said where are you getting sb->s_user_ns != &init_user_ns
>> for an xfs filesystem?

James please answer this question:

 Where are you getting sb->s_user_ns != &init_user_ns for an xfs filesystem?

None of this matters if sb->s_user_ns == &init_user_ns.

This is signification because only xfs keeps any in-core data structure
in it's on-disk encoding.  So this problem is xfs specific.   So
understanding how you are getting xfs to have sb->s_user_ns !=
&init_user_ns is important for discussing which direction we go with
helper functions here.

xfs with sb->s_user_ns == &init_user_ns is perfectly fine and as such no
fixes are needed.

Eric
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