[PATCH] btrfs: Avoid potential integer overflow when left-shifting 32-bit int

[Nur Hussein <hussein@unixcat.org>]

In scrub_stripe(), the 32-bit signed value returned by the
nr_data_stripes(map) function call should be cast to u64
before being shifted left by BTRFS_STRIPE_LEN_SHIFT (16),
as a cautionary measure to avoid potential overflows. We
then assign it to a u64 value anyway, so a cast before a
shift seems prudent.

Signed-off-by: Nur Hussein <hussein@unixcat.org>
---
 fs/btrfs/scrub.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index ccb4f58ae307..4de1665fcd52 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2187,7 +2187,7 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 
 	/* Initialize @offset in case we need to go to out: label */
 	get_raid56_logic_offset(physical, stripe_index, map, &offset, NULL);
-	increment = nr_data_stripes(map) << BTRFS_STRIPE_LEN_SHIFT;
+	increment = (u64)nr_data_stripes(map) << BTRFS_STRIPE_LEN_SHIFT;
 
 	/*
 	 * Due to the rotation, for RAID56 it's better to iterate each stripe
-- 
2.34.1