[RFC PATCH 02/10] mm, swap: skip swap devices without a block device in hibernation lookups

[Youngjun Park <youngjun.park@lge.com>]

A swapfile on NFS or SMB3 has no block device, so claim_swapfile()
leaves si->bdev NULL.  __find_hibernation_swap_type() and
find_first_swap() dereference it without checking.

Hibernation cannot use such a device anyway.  Skip it.

Fixes: 21bd900572f3 ("mm: split swap_type_of")
Assisted-by: Claude:claude-fable-5
Signed-off-by: Youngjun Park <youngjun.park@lge.com>
---
 mm/swapfile.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 592ca26a5c0b..655f2647472c 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2238,7 +2238,7 @@ static int __find_hibernation_swap_type(dev_t device, sector_t offset)
 	for (type = 0; type < nr_swapfiles; type++) {
 		struct swap_info_struct *sis = swap_info[type];
 
-		if (!(sis->flags & SWP_WRITEOK))
+		if (!(sis->flags & SWP_WRITEOK) || !sis->bdev)
 			continue;
 
 		if (device == sis->bdev->bd_dev) {
@@ -2425,7 +2425,7 @@ int find_first_swap(dev_t *device)
 	for (type = 0; type < nr_swapfiles; type++) {
 		struct swap_info_struct *sis = swap_info[type];
 
-		if (!(sis->flags & SWP_WRITEOK))
+		if (!(sis->flags & SWP_WRITEOK) || !sis->bdev)
 			continue;
 		*device = sis->bdev->bd_dev;
 		spin_unlock(&swap_lock);
-- 
2.48.1