[merged mm-nonmm-stable] fs-gracefully-handle-get_block-not-mapping-bh-in-__mpage_writepage.patch removed from -mm tree

[merged mm-nonmm-stable] fs-gracefully-handle-get_block-not-mapping-bh-in-__mpage_writepage.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: fs: gracefully handle ->get_block not mapping bh in __mpage_writepage
has been removed from the -mm tree.  Its filename was
     fs-gracefully-handle-get_block-not-mapping-bh-in-__mpage_writepage.patch

This patch was dropped because it was merged into the mm-nonmm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Jan Kara <jack@suse.cz>
Subject: fs: gracefully handle ->get_block not mapping bh in __mpage_writepage
Date: Thu, 26 Jan 2023 09:51:55 +0100

When filesystem's ->get_block function does not map the buffer head when
called from __mpage_writepage(), __mpage_writepage() will happily go and
pass bogus bdev and block number to bio allocation routines which leads to
crashes sooner or later.

E.g.  UDF can do this because it doesn't want to allocate blocks from
->writepages callbacks.  It allocates blocks on write or page fault but
writeback can still spot dirty buffers without underlying blocks allocated
e.g.  if blocksize < pagesize, the tail page is dirtied (which means all
its buffers are dirtied), and truncate extends the file so that some
buffer starts to be within i_size.

Link: https://lkml.kernel.org/r/20230126085155.26395-1-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/fs/mpage.c~fs-gracefully-handle-get_block-not-mapping-bh-in-__mpage_writepage
+++ a/fs/mpage.c
@@ -532,6 +532,8 @@ static int __mpage_writepage(struct page
 		map_bh.b_size = 1 << blkbits;
 		if (mpd->get_block(inode, block_in_file, &map_bh, 1))
 			goto confused;
+		if (!buffer_mapped(&map_bh))
+			goto confused;
 		if (buffer_new(&map_bh))
 			clean_bdev_bh_alias(&map_bh);
 		if (buffer_boundary(&map_bh)) {
_

Patches currently in -mm which might be from jack@suse.cz are