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

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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: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
This commit is contained in:
Darrick J. Wong 2018-06-21 23:26:58 -07:00
parent a3a374bf18
commit e53c4b5983
1 changed files with 16 additions and 1 deletions
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17
fs/xfs/xfs_bmap_util.c
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@ -1187,7 +1187,22 @@ xfs_free_file_space(
return 0; return 0;
if (offset + len > XFS_ISIZE(ip)) if (offset + len > XFS_ISIZE(ip))
len = XFS_ISIZE(ip) - offset; 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;
} }
/* /*