There's a slight problem (other than HCH not liking it) with this
approach of passing the open file in iattr:  for special files, the
struct file pointer makes no sense to the filesystem, since it is always
opened by the generic functions.

This wasn't a problem with ftruncate(), because that one only works on
regular files, but fchmod/fchown/futimes will work on special files as
well, and the filesystem interpreting file->private_data could cause
nasty bugs. 

So I think the correct solution (which was suggested by Trond and
others) is to define an f_op->fsetattr() method, which interested
filesystems can define.


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yeah that does sound like the way to go, thank Miklos

regards
john
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So what do you think where the inodes come from for syscalls like fchmod? Out 
of struct file, of course. But your f_op->getattr and f_op->setattr patches 
are meant for passing struct file down to filesystems anyway, so that 

That's nothing but a replacement for ATTR_FILE and iattr->ia_file. Except by 
removing the ATTR_FILE flag, LSMs will no longer get that information for 
distinguishing file descriptor operations from other operations.

AppArmor needs to know when notify_change is called on a file descriptor, but 
it doesn't care about the file descriptor itself. So any way of passing along 
that information will be fine.

Thanks,
Andreas
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For special files, f_op->fsetattr will be NULL, since
init_special_inode() will set up i_fop that way.

So the filesystem's fsetattr() will only be called for regular files
and/or directories, depending on how it sets up i_fop.

With the ia_file thing, the filesystem would receive the struct file
pointer in all cases.  So the posted patch would break AFS and FUSE,
because they unconditionally use ia_file if available and don't check
the file type.  They could check the file type, but still the interface

Ah, so if we kept ATTR_FILE and got rid of iattr_file, would that be OK
for AppArmor? 

Thanks,
Miklos

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No problem, yes.

Thanks,
Andreas
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