linux-kernel - [PATCH][next][V2] fs/jfs: fix potential integer overflow on shift of a int

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Message-Id: <20210211130108.171493-1-colin.king@canonical.com>
Date:   Thu, 11 Feb 2021 13:01:08 +0000
From:   Colin King <colin.king@...onical.com>
To:     Dave Kleikamp <shaggy@...nel.org>,
        jfs-discussion@...ts.sourceforge.net
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next][V2] fs/jfs: fix potential integer overflow on shift of a int

From: Colin Ian King <colin.king@...onical.com>

The left shift of int 32 bit integer constant 1 is evaluated using 32 bit
arithmetic and then assigned to a signed 64 bit integer. In the case where
l2nb is 32 or more this can lead to an overflow.  Avoid this by shifting
the value 1LL instead.

Addresses-Coverity: ("Uninitentional integer overflow")
Fixes: b40c2e665cd5 ("fs/jfs: TRIM support for JFS Filesystem")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---

V2: shift 1LL rather than using BIT_ULL macro as suggested by
    Dave Kleikamp.

---
 fs/jfs/jfs_dmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 94b7c1cb5ceb..7aee15608619 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -1656,7 +1656,7 @@ s64 dbDiscardAG(struct inode *ip, int agno, s64 minlen)
 		} else if (rc == -ENOSPC) {
 			/* search for next smaller log2 block */
 			l2nb = BLKSTOL2(nblocks) - 1;
-			nblocks = 1 << l2nb;
+			nblocks = 1LL << l2nb;
 		} else {
 			/* Trim any already allocated blocks */
 			jfs_error(bmp->db_ipbmap->i_sb, "-EIO\n");
-- 
2.30.0