Re: [PATCH] xfs_fsr: more selinux fixes

[Brian Foster <bfoster@redhat.com>]

On Wed, Nov 11, 2015 at 03:52:55PM -0600, Eric Sandeen wrote:
> Commit:
> 
> 1adfe5c xfs_fsr: fix SWAPEXT failures under selinux
> 
> attempted to fix up the fork offset under selinux, where
> the temp file is created with a local attribute, but the
> target file has remote attributes; this can lead to a smaller
> data area in the temp inode, without enough room to swap extents
> from the target inode.  I remedied this by pushing the temp
> file attribute to remote, but *only* if the target file's attr
> was also remote.
> 
> However, I have a case from the field where the parent dir
> and the target file both have a context of:
> 
> system_u:object_r:samba_share_t:s0
> 
> but new files created in the dir have a context of
> 
> unconfined_u:object_r:samba_share_t:s0
> 
> This means the temp file has a smaller forkoff, and less space
> in the inode for data, so we fail to swap the extents between
> the two, because they don't fit.
> 
> The following patch fixes this by allowing xfs_fsr to
> kick the tempfile's attr out of local format even if the target
> file's attr is local, if this will move the forkoff in the right
> direction.  This does pass all our fsr xfstests, though I'm not
> sure we have any real coverage of fsr under selinux...
> 
> The only functional change is the test at the very end of the
> patch; the rest is comments, ascii art, and removing the
> now-extraneous XFS_IOC_FSGETXATTRA ioctl.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
> 
> diff --git a/fsr/xfs_fsr.c b/fsr/xfs_fsr.c
> index c8ef18f..68b9819 100644
> --- a/fsr/xfs_fsr.c
> +++ b/fsr/xfs_fsr.c
...
>  			/*
> -			 * If target attr area is less than the temp's (diff < 0)
> -			 * and the target is not local, write a big attr to
> -			 * the temp file to knock the attr out of local format,
> -			 * to match the target.  (This should actually *increase*
> -			 * the temp file's forkoffset when the attr moves out
> -			 * of the inode)
> +			 * If target attr area is less than the temp's
> +			 * (diff < 0), write a big attr to the temp file to knock
> +			 * the attr out of local format.
> +			 * (This should actually *increase* the temp file's
> +			 * forkoffset when the attr moves out of the inode)
>  			 */
> - 			if (diff < 0 && fsx.fsx_nextents > 0) {
> + 			if (diff < 0) {

Space before tab issue on the line above. Looks fine otherwise, but I
wonder if it would also be a good idea to add an informative fsrprintf()
here if we proceed when (fsx.fsx_nextents > 0)?

Brian

>  				char val[2048];
>  				memset(val, 'X', 2048);
>  				if (fsetxattr(tfd, name, val, 2048, 0)) {
> 
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