linux-kernel - [PATCH AUTOSEL 5.14 21/21] io_uring: fix off-by-one in BUILD_BUG_ON check of __REQ_F_LAST

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Message-Id: <20210917023315.816225-21-sashal@kernel.org>
Date:   Thu, 16 Sep 2021 22:33:15 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Hao Xu <haoxu@...ux.alibaba.com>, Jens Axboe <axboe@...nel.dk>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 5.14 21/21] io_uring: fix off-by-one in BUILD_BUG_ON check of __REQ_F_LAST_BIT

From: Hao Xu <haoxu@...ux.alibaba.com>

[ Upstream commit 32c2d33e0b7c4ea53284d5d9435dd022b582c8cf ]

Build check of __REQ_F_LAST_BIT should be larger than, not equal or larger
than. It's perfectly valid to have __REQ_F_LAST_BIT be 32, as that means
that the last valid bit is 31 which does fit in the type.

Signed-off-by: Hao Xu <haoxu@...ux.alibaba.com>
Link: https://lore.kernel.org/r/20210907032243.114190-1-haoxu@linux.alibaba.com
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a2e20a6fbfed..305c9923283a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -10306,7 +10306,7 @@ static int __init io_uring_init(void)
 	BUILD_BUG_ON(SQE_VALID_FLAGS >= (1 << 8));
 
 	BUILD_BUG_ON(ARRAY_SIZE(io_op_defs) != IORING_OP_LAST);
-	BUILD_BUG_ON(__REQ_F_LAST_BIT >= 8 * sizeof(int));
+	BUILD_BUG_ON(__REQ_F_LAST_BIT > 8 * sizeof(int));
 
 	req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC |
 				SLAB_ACCOUNT);
-- 
2.30.2