linux-kernel - Re: [PATCH] fs: jfs: fix shift-out-of-bounds in dbAllocAG

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Date:   Mon, 10 Oct 2022 09:13:51 -0500
From:   Dave Kleikamp <dave.kleikamp@...cle.com>
To:     Dongliang Mu <mudongliangabcd@...il.com>,
        Dongliang Mu <dzm91@...t.edu.cn>
Cc:     syzbot+15342c1aa6a00fb7a438@...kaller.appspotmail.com,
        jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: jfs: fix shift-out-of-bounds in dbAllocAG

On 10/8/22 9:00PM, Dongliang Mu wrote:
> On Thu, Sep 29, 2022 at 1:47 PM Dongliang Mu <dzm91@...t.edu.cn> wrote:
>>
>> From: Dongliang Mu <mudongliangabcd@...il.com>
>>
>> Syzbot found a crash : UBSAN: shift-out-of-bounds in dbAllocAG. The
>> underlying bug is the missing check of bmp->db_agl2size. The field can
>> be greater than 32 and trigger the shift-out-of-bounds.
>>
>> Fix this bug by adding a check of bmp->db_agl2size in dbMount since this
>> field is used in many following functions. Note that, for maintainance,
>> I reorganzie the error handling code of dbMount.
>>
>> Reported-by: syzbot+15342c1aa6a00fb7a438@...kaller.appspotmail.com
>> Signed-off-by: Dongliang Mu <mudongliangabcd@...il.com>
>> ---
>>   fs/jfs/jfs_dmap.c | 21 +++++++++++++++------
>>   1 file changed, 15 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
>> index 6b838d3ae7c2..4c717f245920 100644
>> --- a/fs/jfs/jfs_dmap.c
>> +++ b/fs/jfs/jfs_dmap.c
>> @@ -155,7 +155,7 @@ int dbMount(struct inode *ipbmap)
>>          struct bmap *bmp;
>>          struct dbmap_disk *dbmp_le;
>>          struct metapage *mp;
>> -       int i;
>> +       int i, err;
>>
>>          /*
>>           * allocate/initialize the in-memory bmap descriptor
>> @@ -170,8 +170,8 @@ int dbMount(struct inode *ipbmap)
>>                             BMAPBLKNO << JFS_SBI(ipbmap->i_sb)->l2nbperpage,
>>                             PSIZE, 0);
>>          if (mp == NULL) {
>> -               kfree(bmp);
>> -               return -EIO;
>> +               err = -EIO;
>> +               goto err_kfree_bmp;
>>          }
>>
>>          /* copy the on-disk bmap descriptor to its in-memory version. */
>> @@ -181,9 +181,8 @@ int dbMount(struct inode *ipbmap)
>>          bmp->db_l2nbperpage = le32_to_cpu(dbmp_le->dn_l2nbperpage);
>>          bmp->db_numag = le32_to_cpu(dbmp_le->dn_numag);
>>          if (!bmp->db_numag) {
>> -               release_metapage(mp);
>> -               kfree(bmp);
>> -               return -EINVAL;
>> +               err = -EINVAL;
>> +               goto err_release_metapage;
>>          }
>>
>>          bmp->db_maxlevel = le32_to_cpu(dbmp_le->dn_maxlevel);
>> @@ -194,6 +193,10 @@ int dbMount(struct inode *ipbmap)
>>          bmp->db_agwidth = le32_to_cpu(dbmp_le->dn_agwidth);
>>          bmp->db_agstart = le32_to_cpu(dbmp_le->dn_agstart);
>>          bmp->db_agl2size = le32_to_cpu(dbmp_le->dn_agl2size);
>> +       if (bmp->db_agl2size >= 32) {
>> +               err = -EINVAL;
>> +               goto err_release_metapage;
>> +       }
>>          for (i = 0; i < MAXAG; i++)
>>                  bmp->db_agfree[i] = le64_to_cpu(dbmp_le->dn_agfree[i]);
>>          bmp->db_agsize = le64_to_cpu(dbmp_le->dn_agsize);
>> @@ -214,6 +217,12 @@ int dbMount(struct inode *ipbmap)
>>          BMAP_LOCK_INIT(bmp);
>>
>>          return (0);
>> +
>> +err_release_metapage:
>> +       release_metapage(mp);
>> +err_kfree_bmp:
>> +       kfree(bmp);
>> +       return err;
>>   }
>>
> 
> ping?

Sorry, it's taking me so long to get to this. It looks good, but I'll 
give it a little better look and push it.

Shaggy

> 
>>
>> --
>> 2.35.1
>>