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: [email protected]
Reported-by: Gerald Gibson <[email protected]>
Signed-off-by: Håkon Bugge <[email protected]>
Link: https://lore.kernel.org/linux-raid/[email protected]
Signed-off-by: Yu Kuai <[email protected]>

0 files changed, 0 insertions, 0 deletions