2022-01-14 06:46:34

by CGEL

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

From: Changcheng Deng <[email protected]>

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 <[email protected]>
Signed-off-by: Changcheng Deng <[email protected]>
---
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

2022-01-18 03:02:22

by Steve French

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

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 <[email protected]> wrote:
>
> From: Changcheng Deng <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Changcheng Deng <[email protected]>
> ---
> 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

2022-01-18 03:02:58

by ronnie sahlberg

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

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 <[email protected]> wrote:
>
> From: Changcheng Deng <[email protected]>
>
> 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 <[email protected]>
> Signed-off-by: Changcheng Deng <[email protected]>
> ---
> 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
>