2018-11-26 14:14:25

by Pan Bian

Subject: [PATCH] ext4: fix possible use after free in ext4_quota_enable

The function frees qf_inode via iput but then pass qf_inode to
lockdep_set_quota_inode on the failure path. This may result in a
use-after-free bug. The patch frees df_inode only when it is never used.

Signed-off-by: Pan Bian <[email protected]>
Fixes: daf647d2dd5("ext4: add lockdep annotations for i_data_sem")
---
fs/ext4/super.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 53ff6c2..35689eb 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5690,9 +5690,9 @@ static int ext4_quota_enable(struct super_block *sb, int type, int format_id,
qf_inode->i_flags |= S_NOQUOTA;
lockdep_set_quota_inode(qf_inode, I_DATA_SEM_QUOTA);
err = dquot_enable(qf_inode, type, format_id, flags);
- iput(qf_inode);
if (err)
lockdep_set_quota_inode(qf_inode, I_DATA_SEM_NORMAL);
+ iput(qf_inode);

return err;
}
--
2.7.4

2018-11-27 20:12:10

by Jan Kara

Subject: Re: [PATCH] ext4: fix possible use after free in ext4_quota_enable

On Mon 26-11-18 11:21:06, Pan Bian wrote:
> The function frees qf_inode via iput but then pass qf_inode to
> lockdep_set_quota_inode on the failure path. This may result in a
> use-after-free bug. The patch frees df_inode only when it is never used.
>
> Signed-off-by: Pan Bian <[email protected]>
> Fixes: daf647d2dd5("ext4: add lockdep annotations for i_data_sem")

Thanks for the fix! The patch looks good. You can add:

Reviewed-by: Jan Kara <[email protected]>

Honza

> ---
> fs/ext4/super.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 53ff6c2..35689eb 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -5690,9 +5690,9 @@ static int ext4_quota_enable(struct super_block *sb, int type, int format_id,
> qf_inode->i_flags |= S_NOQUOTA;
> lockdep_set_quota_inode(qf_inode, I_DATA_SEM_QUOTA);
> err = dquot_enable(qf_inode, type, format_id, flags);
> - iput(qf_inode);
> if (err)
> lockdep_set_quota_inode(qf_inode, I_DATA_SEM_NORMAL);
> + iput(qf_inode);
>
> return err;
> }
> --
> 2.7.4
>
>
--
Jan Kara <[email protected]>
SUSE Labs, CR

2018-12-04 04:33:24

by Theodore Ts'o

Subject: Re: [PATCH] ext4: fix possible use after free in ext4_quota_enable

On Tue, Nov 27, 2018 at 10:14:53AM +0100, Jan Kara wrote:
> On Mon 26-11-18 11:21:06, Pan Bian wrote:
> > The function frees qf_inode via iput but then pass qf_inode to
> > lockdep_set_quota_inode on the failure path. This may result in a
> > use-after-free bug. The patch frees df_inode only when it is never used.
> >
> > Signed-off-by: Pan Bian <[email protected]>
> > Fixes: daf647d2dd5("ext4: add lockdep annotations for i_data_sem")
>
> Thanks for the fix! The patch looks good. You can add:
>
> Reviewed-by: Jan Kara <[email protected]>

Thanks, applied.

- Ted