cifs: Replace one-element array with flexible-array member

[PATCH] cifs: Replace one-element array with flexible-array member

Posted by cgel.zte@gmail.com 4 years, 5 months ago

From: Changcheng Deng <deng.changcheng@zte.com.cn>

There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use "flexible array members" for these cases. The older
style of one-element or zero-length arrays should no longer be used.
Reference:
https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
---
 fs/cifs/smb2ops.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index af5d0830bc8a..5c104b2f308a 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -1609,10 +1609,10 @@ struct iqi_vars {
 	struct smb_rqst rqst[3];
 	struct kvec rsp_iov[3];
 	struct kvec open_iov[SMB2_CREATE_IOV_SIZE];
-	struct kvec qi_iov[1];
+	struct kvec qi_iov[];
 	struct kvec io_iov[SMB2_IOCTL_IOV_SIZE];
 	struct kvec si_iov[SMB2_SET_INFO_IOV_SIZE];
-	struct kvec close_iov[1];
+	struct kvec close_iov[];
 };
 
 static int
-- 
2.25.1

Re: [PATCH] cifs: Replace one-element array with flexible-array member

Posted by Steve French 4 years, 5 months ago

Doesn't this change the address of the assignment in this line in the
function (smb2_ioctl_query_info)?

        /* Close */
        rqst[2].rq_iov = &vars->close_iov[0];

On Fri, Jan 14, 2022 at 8:44 AM <cgel.zte@gmail.com> wrote:
>
> From: Changcheng Deng <deng.changcheng@zte.com.cn>
>
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use "flexible array members" for these cases. The older
> style of one-element or zero-length arrays should no longer be used.
> Reference:
> https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
>
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
> ---
>  fs/cifs/smb2ops.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index af5d0830bc8a..5c104b2f308a 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -1609,10 +1609,10 @@ struct iqi_vars {
>         struct smb_rqst rqst[3];
>         struct kvec rsp_iov[3];
>         struct kvec open_iov[SMB2_CREATE_IOV_SIZE];
> -       struct kvec qi_iov[1];
> +       struct kvec qi_iov[];
>         struct kvec io_iov[SMB2_IOCTL_IOV_SIZE];
>         struct kvec si_iov[SMB2_SET_INFO_IOV_SIZE];
> -       struct kvec close_iov[1];
> +       struct kvec close_iov[];
>  };
>
>  static int
> --
> 2.25.1
>


-- 
Thanks,

Steve

Re: [PATCH] cifs: Replace one-element array with flexible-array member

Posted by ronnie sahlberg 4 years, 5 months ago

This patch is wrong.
qi_iov is not even the trailing element of the array so we cant change
it to be a flexible array member.
This change will likely clobber io_iov so the potential for breaking,
memory leaks or ooops is quite possible.
qi_iov is supposed to be exactly one element in size.

Same for close_iov, while it is the last element in the structure, it
is not a flexible array but an array of exactly one member.
This change to close_iov would likely lead to reading/writing beyond
the end of the structure.


NACK

On Sat, Jan 15, 2022 at 12:44 AM <cgel.zte@gmail.com> wrote:
>
> From: Changcheng Deng <deng.changcheng@zte.com.cn>
>
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use "flexible array members" for these cases. The older
> style of one-element or zero-length arrays should no longer be used.
> Reference:
> https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
>
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Changcheng Deng <deng.changcheng@zte.com.cn>
> ---
>  fs/cifs/smb2ops.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index af5d0830bc8a..5c104b2f308a 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -1609,10 +1609,10 @@ struct iqi_vars {
>         struct smb_rqst rqst[3];
>         struct kvec rsp_iov[3];
>         struct kvec open_iov[SMB2_CREATE_IOV_SIZE];
> -       struct kvec qi_iov[1];
> +       struct kvec qi_iov[];
>         struct kvec io_iov[SMB2_IOCTL_IOV_SIZE];
>         struct kvec si_iov[SMB2_SET_INFO_IOV_SIZE];
> -       struct kvec close_iov[1];
> +       struct kvec close_iov[];
>  };
>
>  static int
> --
> 2.25.1
>