linux-kernel - [PATCH] linux/bitmap.h: fix potential sign-extension overflow

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Date:   Tue, 15 Oct 2019 13:46:57 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     William Breathitt Gray <vilhelm.gray@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] linux/bitmap.h: fix potential sign-extension overflow

In expression 0xff << offset, left shifting by more than 31 bits has
undefined behavior. Notice that the shift amount, *offset*, can be as
much as 63.

Fix this by adding suffix ULL to integer 0xFF.

Addresses-Coverity: 1487071 ("Bad bit shift operation")
Fixes: d33f5cbaadd8 ("bitops: introduce the for_each_set_clump8 macro")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 include/linux/bitmap.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 942871bfe47e..96f91db25b06 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -520,7 +520,7 @@ static inline void bitmap_set_value8(unsigned long *map, unsigned long value,
 	const size_t index = BIT_WORD(start);
 	const unsigned long offset = start % BITS_PER_LONG;
 
-	map[index] &= ~(0xFF << offset);
+	map[index] &= ~(0xFFULL << offset);
 	map[index] |= value << offset;
 }
 
-- 
2.23.0