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Commit e53c4b59 authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: ensure post-EOF zeroing happens after zeroing part of a file 



If a user asks us to zero_range part of a file, the end of the range is
EOF, and not aligned to a page boundary, invoke writeback of the EOF
page to ensure that the post-EOF part of the page is zeroed.  This
ensures that we don't expose stale memory contents via mmap, if in a
clumsy manner.

Found by running generic/127 when it runs zero_range and mapread at EOF
one after the other.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarAllison Henderson <allison.henderson@oracle.com>
parent a3a374bf

fs/xfs/xfs_bmap_util.c

+16 −1
Original line number Diff line number Diff line
@@ -1187,7 +1187,22 @@ xfs_free_file_space( 
		return 0;

	if (offset + len > XFS_ISIZE(ip))

		len = XFS_ISIZE(ip) - offset;

	return iomap_zero_range(VFS_I(ip), offset, len, NULL, &xfs_iomap_ops);

	error = iomap_zero_range(VFS_I(ip), offset, len, NULL, &xfs_iomap_ops);

	if (error)

		return error;



	/*

	 * If we zeroed right up to EOF and EOF straddles a page boundary we

	 * must make sure that the post-EOF area is also zeroed because the

	 * page could be mmap'd and iomap_zero_range doesn't do that for us.

	 * Writeback of the eof page will do this, albeit clumsily.

	 */

	if (offset + len >= XFS_ISIZE(ip) && ((offset + len) & PAGE_MASK)) {

		error = filemap_write_and_wait_range(VFS_I(ip)->i_mapping,

				(offset + len) & ~PAGE_MASK, LLONG_MAX);

	}



	return error;

}



/*