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md: validate bblog_size when loading v1.x badblocks metadata

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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: 2699b67223 ("md: load/store badblock list from v1.x metadata")
Cc: stable@vger.kernel.org
Signed-off-by: Yuchao Zhang <ndaugoing@gmail.com>
Link: https://patch.msgid.link/20260922044606.30774-1-ndaugoing@gmail.com
Signed-off-by: Yu Kuai <yukuai@fygo.io>
This commit is contained in:
Yuchao Zhang 2026-09-22 12:46:06 +08:00 committed by Yu Kuai
parent 7bcc031d49
commit ae5f89b23c
1 changed files with 4 additions and 1 deletions
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5
drivers/md/md.c
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@ -1934,8 +1934,11 @@ static int super_1_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor_
if (!badblocks_set(&rdev->badblocks, sector, count, 1))
return -EINVAL;
}
} else if (sb->bblog_offset != 0)
} else if (sb->bblog_offset != 0) {
if (le16_to_cpu(sb->bblog_size) > (PAGE_SIZE / 512))
return -EINVAL;
rdev->badblocks.shift = 0;
}
if ((le32_to_cpu(sb->feature_map) &
(MD_FEATURE_PPL | MD_FEATURE_MULTIPLE_PPLS))) {