[PATCH 6.1 299/312] erofs: Fix the slab-out-of-bounds in drop_buffers()

Greg Kroah-Hartman
2026-04-08T18:20:21Z

From: Denis Arefev <arefev@swemel.ru>

commit ce529cc25b184e93397b94a8a322128fc0095cbb upstream.

This was accidentally fixed in commit ce529cc25b18, but it's not possible
to accept all the changes, due to the lack of large folios support for
Linux 6.1 kernels, so this is only the actual bug fix that's needed.

[Background]

Syzbot reported that a KASAN slab-out-of-bounds bug was discovered in
the drop_buffers() function [1].

The root cause is that erofs_raw_access_aops does not define .release_folio
and .invalidate_folio. When using iomap-based operations, folio->private
may contain iomap-specific data rather than buffer_heads. Without special
handlers, the kernel may fall back to generic functions (such as
drop_buffers), which incorrectly treat folio->private as a list of
buffer_head structures, leading to incorrect memory interpretation and
out-of-bounds access.

Fix this by explicitly setting .release_folio and .invalidate_folio to the
values of iomap_release_folio and iomap_invalidate_folio, respectively.

[1] https://syzkaller.appspot.com/x/report.txt?x=12e5a142580000

Fixes: 7479c505b4ab ("fs: Convert iomap_readpage to iomap_read_folio")
Reported-by: syzbot+5b886a2e03529dbcef81@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?id=c6aeabd0c4ad2466f63a274faf2a123103f8fbf7
Signed-off-by: Denis Arefev <arefev@swemel.ru>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/erofs/data.c | 2 ++
1 file changed, 2 insertions(+)

--- a/fs/erofs/data.c
+++ b/fs/erofs/data.c
@@ -406,6 +406,8 @@ const struct address_space_operations er
.readahead = erofs_readahead,
.bmap = erofs_bmap,
.direct_IO = noop_direct_IO,
+ .release_folio = iomap_release_folio,
+ .invalidate_folio = iomap_invalidate_folio,
};

#ifdef CONFIG_FS_DAX