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authorDarrick J. Wong <darrick.wong@oracle.com>2018-06-22 09:26:58 +0300
committerDarrick J. Wong <darrick.wong@oracle.com>2018-06-24 21:56:36 +0300
commite53c4b598372001a13901b77649dc1b4afec3e85 (patch)
tree53c14ed955b01e8966afdf4c2ee41f76d2b73427 /fs/xfs/xfs_bmap_util.c
parenta3a374bf1889b1b401b25e6aada3ca4151a99d15 (diff)
downloadlinux-e53c4b598372001a13901b77649dc1b4afec3e85.tar.xz
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: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Diffstat (limited to 'fs/xfs/xfs_bmap_util.c')
-rw-r--r--fs/xfs/xfs_bmap_util.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index bb417156e3bf..83b1e8c6c18f 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -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;
}
/*