md/md-bitmap: fix GPF in bitmap_get_stats()

The commit message of commit 6ec1f0239485 ("md/md-bitmap: fix stats
collection for external bitmaps") states:

    Remove the external bitmap check as the statistics should be
    available regardless of bitmap storage location.

    Return -EINVAL only for invalid bitmap with no storage (neither in
    superblock nor in external file).

But, the code does not adhere to the above, as it does only check for
a valid super-block for "internal" bitmaps. Hence, we observe:

Oops: GPF, probably for non-canonical address 0x1cd66f1f40000028
RIP: 0010:bitmap_get_stats+0x45/0xd0
Call Trace:

 seq_read_iter+0x2b9/0x46a
 seq_read+0x12f/0x180
 proc_reg_read+0x57/0xb0
 vfs_read+0xf6/0x380
 ksys_read+0x6d/0xf0
 do_syscall_64+0x8c/0x1b0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

We fix this by checking the existence of a super-block for both the
internal and external case.

Fixes: 6ec1f0239485 ("md/md-bitmap: fix stats collection for external bitmaps")
Cc: stable@vger.kernel.org
Reported-by: Gerald Gibson <gerald.gibson@oracle.com>
Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Link: https://lore.kernel.org/linux-raid/20250702091035.2061312-1-haakon.bugge@oracle.com
Signed-off-by: Yu Kuai <yukuai3@huawei.com>

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index bd694910b01b0b5ed27712c468d31070afb2284b..7f524a26cebcaac84ce1866ad2da5940ad90d6b1 100644 (file)
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -2366,8 +2366,7 @@ static int bitmap_get_stats(void *data, struct md_bitmap_stats *stats)
 
        if (!bitmap)
                return -ENOENT;
-       if (!bitmap->mddev->bitmap_info.external &&
-           !bitmap->storage.sb_page)
+       if (!bitmap->storage.sb_page)
                return -EINVAL;
        sb = kmap_local_page(bitmap->storage.sb_page);
        stats->sync_size = le64_to_cpu(sb->sync_size);