2021-02-11 13:26:11

by Colin King

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

From: Colin Ian King <[email protected]>

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 <[email protected]>
---

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

2021-02-11 18:17:01

by Dave Kleikamp

Subject: Re: [PATCH][next][V2] fs/jfs: fix potential integer overflow on shift of a int

On 2/11/21 7:01 AM, Colin King wrote:
> From: Colin Ian King <[email protected]>
>
> 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 <[email protected]>

Looks good. I'll include it in the next jfs drop.

Thanks,
Shaggy

> ---
>
> 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");
>