btrfs: fix remaining u32 overflows when left shifting stripe_nr

There was regression caused by a97699d1d610 ("btrfs: replace
map_lookup->stripe_len by BTRFS_STRIPE_LEN") and supposedly fixed by
a7299a18a179 ("btrfs: fix u32 overflows when left shifting stripe_nr").
To avoid code churn the fix was open coding the type casts but
unfortunately missed one which was still possible to hit [1].

The missing place was assignment of bioc->full_stripe_logical inside
btrfs_map_block().

Fix it by adding a helper that does the safe calculation of the offset
and use it everywhere even though it may not be strictly necessary due
to already using u64 types.  This replaces all remaining
"<< BTRFS_STRIPE_LEN_SHIFT" calls.

[1] https://lore.kernel.org/linux-btrfs/20230622065438.86402-1-wqu@suse.com/

Fixes: a7299a18a179 ("btrfs: fix u32 overflows when left shifting stripe_nr")
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index bf47a1a70813..64066d48dce1 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -574,6 +574,17 @@ static inline unsigned long btrfs_chunk_item_size(int num_stripes)
 		sizeof(struct btrfs_stripe) * (num_stripes - 1);
 }
 
+/*
+ * Do the type safe converstion from stripe_nr to offset inside the chunk.
+ *
+ * @stripe_nr is u32, with left shift it can overflow u32 for chunks larger
+ * than 4G.  This does the proper type cast to avoid overflow.
+ */
+static inline u64 btrfs_stripe_nr_to_offset(u32 stripe_nr)
+{
+	return (u64)stripe_nr << BTRFS_STRIPE_LEN_SHIFT;
+}
+
 void btrfs_get_bioc(struct btrfs_io_context *bioc);
 void btrfs_put_bioc(struct btrfs_io_context *bioc);
 int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,