[cifs:for-next 24/31] fs/cifs/smb2ops.c:4056 smb2_decrypt_offload() error: we previously assumed 'mid' could be null (see line 4045)

[Pavel Shilovsky]

Yes, this is a bug.

Steve, let's move

+       mid->callback(mid);
+
+       cifs_mid_q_entry_release(mid);

under ELSE {} block above.

We should probably move

+       dw->server->lstrp = jiffies;

before we looking for a mid.

--
Best regards,
Pavel Shilovsky

пт, 13 сент. 2019 г. в 06:47, Dan Carpenter <dan.carpenter at oracle.com>:
>
> tree:   git://git.samba.org/sfrench/cifs-2.6.git for-next
> head:   5fc321fb644fc787710353be11129edadd313f3a
> commit: a091c5f67c994d154e8faf95ab774644be2f4dd7 [24/31] smb3: allow parallelizing decryption of reads
>
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp at intel.com>
> Reported-by: Dan Carpenter <dan.carpenter at oracle.com>
>
> New smatch warnings:
> fs/cifs/smb2ops.c:4056 smb2_decrypt_offload() error: we previously assumed 'mid' could be null (see line 4045)
>
> git remote add cifs git://git.samba.org/sfrench/cifs-2.6.git
> git remote update cifs
> git checkout a091c5f67c994d154e8faf95ab774644be2f4dd7
> vim +/mid +4056 fs/cifs/smb2ops.c
>
> a091c5f67c994d Steve French 2019-09-07  4030  static void smb2_decrypt_offload(struct work_struct *work)
> a091c5f67c994d Steve French 2019-09-07  4031  {
> a091c5f67c994d Steve French 2019-09-07  4032    struct smb2_decrypt_work *dw = container_of(work,
> a091c5f67c994d Steve French 2019-09-07  4033                            struct smb2_decrypt_work, decrypt);
> a091c5f67c994d Steve French 2019-09-07  4034    int i, rc;
> a091c5f67c994d Steve French 2019-09-07  4035    struct mid_q_entry *mid;
> a091c5f67c994d Steve French 2019-09-07  4036
> a091c5f67c994d Steve French 2019-09-07  4037    rc = decrypt_raw_data(dw->server, dw->buf, dw->server->vals->read_rsp_size,
> a091c5f67c994d Steve French 2019-09-07  4038                          dw->ppages, dw->npages, dw->len);
> a091c5f67c994d Steve French 2019-09-07  4039    if (rc) {
> a091c5f67c994d Steve French 2019-09-07  4040            cifs_dbg(VFS, "error decrypting rc=%d\n", rc);
> a091c5f67c994d Steve French 2019-09-07  4041            goto free_pages;
> a091c5f67c994d Steve French 2019-09-07  4042    }
> a091c5f67c994d Steve French 2019-09-07  4043
> a091c5f67c994d Steve French 2019-09-07  4044    mid = smb2_find_mid(dw->server, dw->buf);
> a091c5f67c994d Steve French 2019-09-07 @4045    if (mid == NULL)
> a091c5f67c994d Steve French 2019-09-07  4046            cifs_dbg(FYI, "mid not found\n");
>
> Return here?
>
> a091c5f67c994d Steve French 2019-09-07  4047    else {
> a091c5f67c994d Steve French 2019-09-07  4048            mid->decrypted = true;
> a091c5f67c994d Steve French 2019-09-07  4049            rc = handle_read_data(dw->server, mid, dw->buf,
> a091c5f67c994d Steve French 2019-09-07  4050                                  dw->server->vals->read_rsp_size,
> a091c5f67c994d Steve French 2019-09-07  4051                                  dw->ppages, dw->npages, dw->len);
> a091c5f67c994d Steve French 2019-09-07  4052    }
> a091c5f67c994d Steve French 2019-09-07  4053
> a091c5f67c994d Steve French 2019-09-07  4054    dw->server->lstrp = jiffies;
> a091c5f67c994d Steve French 2019-09-07  4055
> a091c5f67c994d Steve French 2019-09-07 @4056    mid->callback(mid);
>                                                 ^^^^^^^^^^^^^
> Potential NULL derference.
>
> a091c5f67c994d Steve French 2019-09-07  4057
> a091c5f67c994d Steve French 2019-09-07  4058    cifs_mid_q_entry_release(mid);
> a091c5f67c994d Steve French 2019-09-07  4059
> a091c5f67c994d Steve French 2019-09-07  4060  free_pages:
> a091c5f67c994d Steve French 2019-09-07  4061    for (i = dw->npages-1; i >= 0; i--)
> a091c5f67c994d Steve French 2019-09-07  4062            put_page(dw->ppages[i]);
> a091c5f67c994d Steve French 2019-09-07  4063
> a091c5f67c994d Steve French 2019-09-07  4064    kfree(dw->ppages);
> a091c5f67c994d Steve French 2019-09-07  4065    cifs_small_buf_release(dw->buf);
> a091c5f67c994d Steve French 2019-09-07  4066  }
>
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation