Re: [PATCH v2] md: validate bblog_size when loading v1.x badblocks metadata

[yu kuai]

在 2026/9/22 12:46, Yuchao Zhang 写道:

> In super_1_load(), when the on-disk feature_map does not have
> MD_FEATURE_BAD_BLOCKS set but sb->bblog_offset is non-zero,
> rdev->badblocks.shift is initialized to 0 without validating
> sb->bblog_size.  The same field is validated in the
> MD_FEATURE_BAD_BLOCKS branch ("sectors > (PAGE_SIZE / 512)"), but this
> branch bypasses that check.
>
> A forged on-disk superblock (malicious storage device or crafted
> image) can therefore carry an oversized sb->bblog_size.  When bad
> blocks are later recorded, super_1_sync() sets bb->size from
> sb->bblog_size and md_write_metadata() issues a bio larger than the
> single rdev->bb_page, reading beyond the page and leaking kernel
> memory contents to disk.
>
> sb->bblog_size is never modified by the kernel between load and sync,
> and the MD_FEATURE_BAD_BLOCKS branch already validates it, so checking
> it in this branch is sufficient to cover both paths.
>
> Fix this by rejecting an oversized sb->bblog_size with -EINVAL,
> matching the existing check in the MD_FEATURE_BAD_BLOCKS branch.
>
> Fixes: 2699b67223ac ("md: load/store badblock list from v1.x metadata")
> Cc:stable@xxxxxxxxxxxxxxx
> Signed-off-by: Yuchao Zhang<ndaugoing@xxxxxxxxx>
> ---
>   drivers/md/md.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
Applied to md-7.4

-- 
Thanks,
Kuai