[PATCH v2] block: reject bs > ps block devices when THP is disabled

["Pankaj Raghav (Samsung)" <kernel@pankajraghav.com>]

From: Pankaj Raghav <p.raghav@samsung.com>

If THP is disabled and when a block device with logical block size >
page size is present, the following null ptr deref panic happens during
boot:

[   [13.2 mK  AOSAN: null-ptr-deref in range [0x0000000000000000-0x0000000000K0 0 0[07]
[   13.017749] RIP: 0010:create_empty_buffers+0x3b/0x380
<snip>
[   13.025448] Call Trace:
[   13.025692]  <TASK>
[   13.025895]  block_read_full_folio+0x610/0x780
[   13.026379]  ? __pfx_blkdev_get_block+0x10/0x10
[   13.027008]  ? __folio_batch_add_and_move+0x1fa/0x2b0
[   13.027548]  ? __pfx_blkdev_read_folio+0x10/0x10
[   13.028080]  filemap_read_folio+0x9b/0x200
[   13.028526]  ? __pfx_filemap_read_folio+0x10/0x10
[   13.029030]  ? __filemap_get_folio+0x43/0x620
[   13.029497]  do_read_cache_folio+0x155/0x3b0
[   13.029962]  ? __pfx_blkdev_read_folio+0x10/0x10
[   13.030381]  read_part_sector+0xb7/0x2a0
[   13.030805]  read_lba+0x174/0x2c0
<snip>
[   13.045348]  nvme_scan_ns+0x684/0x850 [nvme_core]
[   13.045858]  ? __pfx_nvme_scan_ns+0x10/0x10 [nvme_core]
[   13.046414]  ? _raw_spin_unlock+0x15/0x40
[   13.046843]  ? __switch_to+0x523/0x10a0
[   13.047253]  ? kvm_clock_get_cycles+0x14/0x30
[   13.047742]  ? __pfx_nvme_scan_ns_async+0x10/0x10 [nvme_core]
[   13.048353]  async_run_entry_fn+0x96/0x4f0
[   13.048787]  process_one_work+0x667/0x10a0
[   13.049219]  worker_thread+0x63c/0xf60

As large folio support depends on THP, only allow bs > ps block devices
if THP is enabled.

Fixes: 47dd67532303 ("block/bdev: lift block size restrictions to 64k")
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
---
Changes since v1:
- Use mapping_max_folio_size_supported() instead of doing a ifdef with
  CONFIG_THP

 include/linux/blkdev.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 82348fcc2455..0c22ad8120da 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -26,6 +26,7 @@
 #include <linux/xarray.h>
 #include <linux/file.h>
 #include <linux/lockdep.h>
+#include <linux/pagemap.h>
 
 struct module;
 struct request_queue;
@@ -274,7 +275,7 @@ static inline dev_t disk_devt(struct gendisk *disk)
  * We should strive for 1 << (PAGE_SHIFT + MAX_PAGECACHE_ORDER)
  * however we constrain this to what we can validate and test.
  */
-#define BLK_MAX_BLOCK_SIZE      SZ_64K
+#define BLK_MAX_BLOCK_SIZE (min(mapping_max_folio_size_supported(), SZ_64K))
 
 /* blk_validate_limits() validates bsize, so drivers don't usually need to */
 static inline int blk_validate_block_size(unsigned long bsize)

base-commit: 8d6c58332c7a8ba025fcfa76888b6c37dbce9633
-- 
2.49.0