From: Yang Erkun <yangerkun@huawei.com> mainline inclusion from mainline-v6.17-rc1 commit 13017b427118f4311471ee47df74872372ca8482 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ICUC8X CVE: CVE-2025-38621 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... ------------------ Our testcase trigger panic: BUG: kernel NULL pointer dereference, address: 00000000000000e0 ... Oops: Oops: 0000 [#1] SMP NOPTI CPU: 2 UID: 0 PID: 85 Comm: kworker/2:1 Not tainted 6.16.0+ #94 PREEMPT(none) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 Workqueue: md_misc md_start_sync RIP: 0010:rdev_addable+0x4d/0xf0 ... Call Trace: <TASK> md_start_sync+0x329/0x480 process_one_work+0x226/0x6d0 worker_thread+0x19e/0x340 kthread+0x10f/0x250 ret_from_fork+0x14d/0x180 ret_from_fork_asm+0x1a/0x30 </TASK> Modules linked in: raid10 CR2: 00000000000000e0 ---[ end trace 0000000000000000 ]--- RIP: 0010:rdev_addable+0x4d/0xf0 md_spares_need_change in md_start_sync will call rdev_addable which protected by rcu_read_lock/rcu_read_unlock. This rcu context will help protect rdev won't be released, but rdev->mddev will be set to NULL before we call synchronize_rcu in md_kick_rdev_from_array. Fix this by using READ_ONCE and check does rdev->mddev still alive. Fixes: bc08041b32ab ("md: suspend array in md_start_sync() if array need reconfiguration") Fixes: 570b9147deb6 ("md: use RCU lock to protect traversal in md_spares_need_change()") Signed-off-by: Yang Erkun <yangerkun@huawei.com> Link: https://lore.kernel.org/linux-raid/20250731114530.776670-1-yangerkun@huawei.... Signed-off-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Zheng Qixing <zhengqixing@huawei.com> --- drivers/md/md.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 4f7284beb754..715f6be52ea7 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -9326,6 +9326,12 @@ static bool rdev_is_spare(struct md_rdev *rdev) static bool rdev_addable(struct md_rdev *rdev) { + struct mddev *mddev; + + mddev = READ_ONCE(rdev->mddev); + if (!mddev) + return false; + /* rdev is already used, don't add it again. */ if (test_bit(Candidate, &rdev->flags) || rdev->raid_disk >= 0 || test_bit(Faulty, &rdev->flags)) @@ -9336,7 +9342,7 @@ static bool rdev_addable(struct md_rdev *rdev) return true; /* Allow to add if array is read-write. */ - if (md_is_rdwr(rdev->mddev)) + if (md_is_rdwr(mddev)) return true; /* -- 2.39.2