[PATCH v2 0/1] ufs: ufs_sb_private_info: remove unused s_{2,3}apb fields

[PATCH v2 0/1] ufs: ufs_sb_private_info: remove unused s_{2,3}apb fields

[Agathe Porte]

v2: add Cc stable because the UBSAN might be triggered of previous
    stable kernels as well.

Agathe Porte (1):
  ufs: ufs_sb_private_info: remove unused s_{2,3}apb fields

 fs/ufs/super.c  | 4 ----
 fs/ufs/ufs_fs.h | 4 ----
 2 files changed, 8 deletions(-)

-- 
2.43.0

[PATCH v2 1/1] ufs: ufs_sb_private_info: remove unused s_{2,3}apb fields

[Agathe Porte]

These two fields are populated during and stored as a "frequently used
value" in ufs_fill_super, but are not used afterwards in the driver.

Moreover, one of the shifts triggers UBSAN: shift-out-of-bounds when
apbshift is 12 because 12 * 3 = 36 and 1 << 36 does not fit in the 32
bit integer used to store the value.

Cc: stable@vger.kernel.org
Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2087853
Signed-off-by: Agathe Porte <agathe.porte@canonical.com>
---
 fs/ufs/super.c  | 4 ----
 fs/ufs/ufs_fs.h | 4 ----
 2 files changed, 8 deletions(-)

diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index bc625788589c..7ea1a4c07ba2 100644
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -1240,11 +1240,7 @@ static int ufs_fill_super(struct super_block *sb, void *data, int silent)
 	else
 		uspi->s_apbshift = uspi->s_bshift - 2;
 
-	uspi->s_2apbshift = uspi->s_apbshift * 2;
-	uspi->s_3apbshift = uspi->s_apbshift * 3;
 	uspi->s_apb = 1 << uspi->s_apbshift;
-	uspi->s_2apb = 1 << uspi->s_2apbshift;
-	uspi->s_3apb = 1 << uspi->s_3apbshift;
 	uspi->s_apbmask = uspi->s_apb - 1;
 	uspi->s_nspfshift = uspi->s_fshift - UFS_SECTOR_BITS;
 	uspi->s_nspb = uspi->s_nspf << uspi->s_fpbshift;
diff --git a/fs/ufs/ufs_fs.h b/fs/ufs/ufs_fs.h
index ef9ead44776a..0905f9a16b91 100644
--- a/fs/ufs/ufs_fs.h
+++ b/fs/ufs/ufs_fs.h
@@ -775,12 +775,8 @@ struct ufs_sb_private_info {
 
 	__u32	s_fpbmask;	/* fragments per block mask */
 	__u32	s_apb;		/* address per block */
-	__u32	s_2apb;		/* address per block^2 */
-	__u32	s_3apb;		/* address per block^3 */
 	__u32	s_apbmask;	/* address per block mask */
 	__u32	s_apbshift;	/* address per block shift */
-	__u32	s_2apbshift;	/* address per block shift * 2 */
-	__u32	s_3apbshift;	/* address per block shift * 3 */
 	__u32	s_nspfshift;	/* number of sector per fragment shift */
 	__u32	s_nspb;		/* number of sector per block */
 	__u32	s_inopf;	/* inodes per fragment */
-- 
2.43.0

Re: [PATCH v2 1/1] ufs: ufs_sb_private_info: remove unused s_{2,3}apb fields

[Greg KH]

On Tue, Nov 12, 2024 at 01:01:54PM +0100, Agathe Porte wrote:
> These two fields are populated during and stored as a "frequently used
> value" in ufs_fill_super, but are not used afterwards in the driver.
> 
> Moreover, one of the shifts triggers UBSAN: shift-out-of-bounds when
> apbshift is 12 because 12 * 3 = 36 and 1 << 36 does not fit in the 32
> bit integer used to store the value.
> 
> Cc: stable@vger.kernel.org
> Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2087853

As these values are not used, even if the shift goes off in the wild
it's not needed to backport this as it's not actually causing any
problems.  So I'd drop the cc: stable@ please.

thanks,

greg k-h

Re: [PATCH v2 1/1] ufs: ufs_sb_private_info: remove unused s_{2,3}apb fields

[Agathe Porte]

On 12/11/2024 13:12, Greg KH wrote:
> On Tue, Nov 12, 2024 at 01:01:54PM +0100, Agathe Porte wrote:
>> These two fields are populated during and stored as a "frequently used
>> value" in ufs_fill_super, but are not used afterwards in the driver.
>>
>> Moreover, one of the shifts triggers UBSAN: shift-out-of-bounds when
>> apbshift is 12 because 12 * 3 = 36 and 1 << 36 does not fit in the 32
>> bit integer used to store the value.
>>
>> Cc: stable@vger.kernel.org
>> Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2087853
> As these values are not used, even if the shift goes off in the wild
> it's not needed to backport this as it's not actually causing any
> problems.  So I'd drop the cc: stable@ please.

OK, sent a v3 that drops the stable cc: 
https://lore.kernel.org/linux-kernel/20241112122000.35610-1-agathe.porte@canonical.com/T/#t