Re: [PATCH v2 1/4] md/raid10: fix slab-out-of-bounds in md_bitmap_get_counter

From: Li Nan
Date: Sun May 14 2023 - 07:15:51 EST

在 2023/5/13 9:05, Song Liu 写道:
On Fri, May 5, 2023 at 6:24 PM <linan666@xxxxxxxxxxxxxxx> wrote:

From: Li Nan <linan122@xxxxxxxxxx>

If we write a large number to md/bitmap_set_bits, md_bitmap_checkpage()
will return -EINVAL because "page >= bitmap->pages", but the return value
was not checked immediately in md_bitmap_get_counter() in order to set
*blocks value and slab-out-of-bounds occurs.

Return directly if err is -EINVAL.

Fixes: ef4256733506 ("md/bitmap: optimise scanning of empty bitmaps.")
Signed-off-by: Li Nan <linan122@xxxxxxxxxx>
Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>
drivers/md/md-bitmap.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index 920bb68156d2..0b41ef422da7 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -1388,6 +1388,8 @@ __acquires(bitmap->lock)
int err;

err = md_bitmap_checkpage(bitmap, page, create, 0);
+ if (err == -EINVAL)
+ return NULL;

This logic is error prone. Since we are on it, let's fix it better.
Specifically, we can move "page >= bitmap->pages" check out

I will check out it in v3.

of md_bitmap_checkpage(). (and fix the call site in md_bitmap_resize
for clustered md).

In md_bitmap_resize(), incoming parameters "page < bitmap->" and do not have this problem.

Also, could you please add a mdadm test for this issue?

It's my pleasure.


if (bitmap->bp[page].hijacked ||
bitmap->bp[page].map == NULL)


Thanks for your suggesion.