From ae5f89b23cb88667cfa1273b42d6a551db9c651e Mon Sep 17 00:00:00 2001 From: Yuchao Zhang Date: Tue, 22 Sep 2026 12:46:06 +0800 Subject: [PATCH] md: validate bblog_size when loading v1.x badblocks metadata 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@vger.kernel.org Signed-off-by: Yuchao Zhang Link: https://patch.msgid.link/20260922044606.30774-1-ndaugoing@gmail.com Signed-off-by: Yu Kuai --- drivers/md/md.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index f443dd927ac3..3cb961036637 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -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))) {