From: Yu Kuai <yukuai3@huawei.com> stable inclusion from stable-v6.6.80 commit 52848a095b55a302af92f52ca0de5b3112059bb8 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBPBEG CVE: CVE-2025-21712 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... ------------------ [ Upstream commit 8d28d0ddb986f56920ac97ae704cc3340a699a30 ] After commit ec6bb299c7c3 ("md/md-bitmap: add 'sync_size' into struct md_bitmap_stats"), following panic is reported: Oops: general protection fault, probably for non-canonical address RIP: 0010:bitmap_get_stats+0x2b/0xa0 Call Trace: <TASK> md_seq_show+0x2d2/0x5b0 seq_read_iter+0x2b9/0x470 seq_read+0x12f/0x180 proc_reg_read+0x57/0xb0 vfs_read+0xf6/0x380 ksys_read+0x6c/0xf0 do_syscall_64+0x82/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e Root cause is that bitmap_get_stats() can be called at anytime if mddev is still there, even if bitmap is destroyed, or not fully initialized. Deferenceing bitmap in this case can crash the kernel. Meanwhile, the above commit start to deferencing bitmap->storage, make the problem easier to trigger. Fix the problem by protecting bitmap_get_stats() with bitmap_info.mutex. Cc: stable@vger.kernel.org # v6.12+ Fixes: 32a7627cf3a3 ("[PATCH] md: optimised resync using Bitmap based intent logging") Reported-and-tested-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com> Closes: https://lore.kernel.org/linux-raid/ca3a91a2-50ae-4f68-b317-abd9889f3907@orac... Signed-off-by: Yu Kuai <yukuai3@huawei.com> Link: https://lore.kernel.org/r/20250124092055.4050195-1-yukuai1@huaweicloud.com Signed-off-by: Song Liu <song@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: drivers/md/md-bitmap.c [Due to not merging commit 38f287d7e495 ("md/md-bitmap: replace md_bitmap_status() with a new helper md_bitmap_get_stats()").] Signed-off-by: Zheng Qixing <zhengqixing@huawei.com> --- drivers/md/md-bitmap.c | 5 ++++- drivers/md/md.c | 5 +++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c index 1398bc6776b9..3744acda47d8 100644 --- a/drivers/md/md-bitmap.c +++ b/drivers/md/md-bitmap.c @@ -2120,7 +2120,10 @@ void md_bitmap_status(struct seq_file *seq, struct bitmap *bitmap) if (!bitmap) return; - + if (bitmap->mddev->bitmap_info.external) + return; + if (!bitmap->storage.sb_page) /* no superblock */ + return; counts = &bitmap->counts; chunk_kb = bitmap->mddev->bitmap_info.chunksize >> 10; diff --git a/drivers/md/md.c b/drivers/md/md.c index 4ef37248b0f0..f2c661af2cc3 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -8340,6 +8340,10 @@ static int md_seq_show(struct seq_file *seq, void *v) return 0; spin_unlock(&all_mddevs_lock); + + /* prevent bitmap to be freed after checking */ + mutex_lock(&mddev->bitmap_info.mutex); + spin_lock(&mddev->lock); if (mddev->pers || mddev->raid_disks || !list_empty(&mddev->disks)) { seq_printf(seq, "%s : %sactive", mdname(mddev), @@ -8410,6 +8414,7 @@ static int md_seq_show(struct seq_file *seq, void *v) seq_printf(seq, "\n"); } spin_unlock(&mddev->lock); + mutex_unlock(&mddev->bitmap_info.mutex); spin_lock(&all_mddevs_lock); if (atomic_dec_and_test(&mddev->active)) __mddev_put(mddev); -- 2.39.2