From 1a33a379e67853d6d778e6e80b214bdf1208f6f8 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?J=C3=A9r=C3=A9my=20Jean?= Date: Thu, 20 Aug 2026 21:07:03 +0000 Subject: [PATCH] md: reject v0.90 arrays with too many devices MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The v0.90 superblock has room for MD_SB_DISKS device descriptors, but super_90_load() only rejects nonpositive raid_disks values. A crafted superblock can therefore copy a larger value into mddev->raid_disks. When metadata is next updated, super_90_sync() walks sb->disks[] up to that count and reads and writes beyond the 4 KiB superblock buffer. A checksum-valid RAID1 member advertising 64 devices can be assembled by mdadm --incremental --run. The first write to the array then produces out-of-bounds writes from super_90_sync() under KASAN. Reject device counts that cannot be represented by the v0.90 format while loading the superblock. Assisted-by: Codex:gpt-5 Signed-off-by: Jérémy Jean Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Link: https://patch.msgid.link/20260820210703.3035608-2-Jeremy.Jean@oss.cyber.gouv.fr Signed-off-by: Yu Kuai --- drivers/md/md.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 680b34a63cb3..154ee5a65cb7 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -1393,7 +1393,7 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor goto abort; } - if (sb->raid_disks <= 0) + if (sb->raid_disks <= 0 || sb->raid_disks > MD_SB_DISKS) goto abort; if (md_csum_fold(calc_sb_csum(sb)) != md_csum_fold(sb->sb_csum)) {