[PATCH] bcachefs: fix shift oob in alloc_lru_idx_fragmentation

[Jeongjun Park <aha310510@gmail.com>]

The size of a.data_type is set abnormally large, causing shift-out-of-bounds.
To fix this, we need to add validation on a.data_type in 
alloc_lru_idx_fragmentation().

Reported-by: syzbot+7f45fa9805c40db3f108@syzkaller.appspotmail.com
Fixes: 260af1562ec1 ("bcachefs: Kill alloc_v4.fragmentation_lru")
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
 fs/bcachefs/alloc_background.h       | 3 +++
 fs/bcachefs/disk_accounting_format.h | 2 ++
 2 files changed, 5 insertions(+)

diff --git a/fs/bcachefs/alloc_background.h b/fs/bcachefs/alloc_background.h
index f8e87c6721b1..66a334e2edcd 100644
--- a/fs/bcachefs/alloc_background.h
+++ b/fs/bcachefs/alloc_background.h
@@ -168,6 +168,9 @@ static inline bool data_type_movable(enum bch_data_type type)
 static inline u64 alloc_lru_idx_fragmentation(struct bch_alloc_v4 a,
 					   struct bch_dev *ca)
 {
+	if (a.data_type > BCH_DATA_TYPE_MAX)
+		return 0;
+	
 	if (!data_type_movable(a.data_type) ||
 	    !bch2_bucket_sectors_fragmented(ca, a))
 		return 0;
diff --git a/fs/bcachefs/disk_accounting_format.h b/fs/bcachefs/disk_accounting_format.h
index 7b6e6c97e6aa..0232bc9f590d 100644
--- a/fs/bcachefs/disk_accounting_format.h
+++ b/fs/bcachefs/disk_accounting_format.h
@@ -72,6 +72,8 @@ enum bch_data_type {
 	BCH_DATA_NR
 };
 
+#define BCH_DATA_TYPE_MAX 10
+
 static inline bool data_type_is_empty(enum bch_data_type type)
 {
 	switch (type) {
--