ksmbd: ipc: use kzalloc_flex and __counted_by

[PATCH] ksmbd: ipc: use kzalloc_flex and __counted_by

Posted by Rosen Penev 1 month ago

The former is just a nice macro and the latter allows runtime analysis
of the allocation and its size.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 fs/smb/server/transport_ipc.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/fs/smb/server/transport_ipc.c b/fs/smb/server/transport_ipc.c
index 2dbabe2d8005..f7aa427a06fe 100644
--- a/fs/smb/server/transport_ipc.c
+++ b/fs/smb/server/transport_ipc.c
@@ -55,7 +55,7 @@ static bool ksmbd_ipc_validate_version(struct genl_info *m)
 struct ksmbd_ipc_msg {
 	unsigned int		type;
 	unsigned int		sz;
-	unsigned char		payload[];
+	unsigned char		payload[] __counted_by(sz);
 };
 
 struct ipc_msg_table_entry {
@@ -242,9 +242,8 @@ static void ipc_update_last_active(void)
 static struct ksmbd_ipc_msg *ipc_msg_alloc(size_t sz)
 {
 	struct ksmbd_ipc_msg *msg;
-	size_t msg_sz = sz + sizeof(struct ksmbd_ipc_msg);
 
-	msg = kvzalloc(msg_sz, KSMBD_DEFAULT_GFP);
+	msg = kvzalloc_flex(*msg, payload, sz, KSMBD_DEFAULT_GFP);
 	if (msg)
 		msg->sz = sz;
 	return msg;
-- 
2.53.0

Re: [PATCH] ksmbd: ipc: use kzalloc_flex and __counted_by

Posted by Namjae Jeon 2 weeks, 1 day ago

On Fri, Mar 6, 2026 at 3:35 PM Rosen Penev <rosenp@gmail.com> wrote:
>
> The former is just a nice macro and the latter allows runtime analysis
> of the allocation and its size.
>
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
> ---
>  fs/smb/server/transport_ipc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/smb/server/transport_ipc.c b/fs/smb/server/transport_ipc.c
> index 2dbabe2d8005..f7aa427a06fe 100644
> --- a/fs/smb/server/transport_ipc.c
> +++ b/fs/smb/server/transport_ipc.c
> @@ -55,7 +55,7 @@ static bool ksmbd_ipc_validate_version(struct genl_info *m)
>  struct ksmbd_ipc_msg {
>         unsigned int            type;
>         unsigned int            sz;
> -       unsigned char           payload[];
> +       unsigned char           payload[] __counted_by(sz);
>  };
>
>  struct ipc_msg_table_entry {
> @@ -242,9 +242,8 @@ static void ipc_update_last_active(void)
>  static struct ksmbd_ipc_msg *ipc_msg_alloc(size_t sz)
>  {
>         struct ksmbd_ipc_msg *msg;
> -       size_t msg_sz = sz + sizeof(struct ksmbd_ipc_msg);
>
> -       msg = kvzalloc(msg_sz, KSMBD_DEFAULT_GFP);
> +       msg = kvzalloc_flex(*msg, payload, sz, KSMBD_DEFAULT_GFP);
>         if (msg)
>                 msg->sz = sz;
We don't need to manually set msg->sz if the flexible array member is
properly annotated with __counted_by(sz) ?
kvmalloc_flex() automatically sets the counter via internal
__set_flex_counter().

Re: [PATCH] ksmbd: ipc: use kzalloc_flex and __counted_by

Posted by Rosen Penev 2 weeks, 1 day ago

On Tue, Mar 24, 2026 at 11:26 PM Namjae Jeon <linkinjeon@kernel.org> wrote:
>
> On Fri, Mar 6, 2026 at 3:35 PM Rosen Penev <rosenp@gmail.com> wrote:
> >
> > The former is just a nice macro and the latter allows runtime analysis
> > of the allocation and its size.
> >
> > Signed-off-by: Rosen Penev <rosenp@gmail.com>
> > ---
> >  fs/smb/server/transport_ipc.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/smb/server/transport_ipc.c b/fs/smb/server/transport_ipc.c
> > index 2dbabe2d8005..f7aa427a06fe 100644
> > --- a/fs/smb/server/transport_ipc.c
> > +++ b/fs/smb/server/transport_ipc.c
> > @@ -55,7 +55,7 @@ static bool ksmbd_ipc_validate_version(struct genl_info *m)
> >  struct ksmbd_ipc_msg {
> >         unsigned int            type;
> >         unsigned int            sz;
> > -       unsigned char           payload[];
> > +       unsigned char           payload[] __counted_by(sz);
> >  };
> >
> >  struct ipc_msg_table_entry {
> > @@ -242,9 +242,8 @@ static void ipc_update_last_active(void)
> >  static struct ksmbd_ipc_msg *ipc_msg_alloc(size_t sz)
> >  {
> >         struct ksmbd_ipc_msg *msg;
> > -       size_t msg_sz = sz + sizeof(struct ksmbd_ipc_msg);
> >
> > -       msg = kvzalloc(msg_sz, KSMBD_DEFAULT_GFP);
> > +       msg = kvzalloc_flex(*msg, payload, sz, KSMBD_DEFAULT_GFP);
> >         if (msg)
> >                 msg->sz = sz;
> We don't need to manually set msg->sz if the flexible array member is
> properly annotated with __counted_by(sz) ?
> kvmalloc_flex() automatically sets the counter via internal
> __set_flex_counter().
Needs GCC15.

Re: [PATCH] ksmbd: ipc: use kzalloc_flex and __counted_by

Posted by Namjae Jeon 2 weeks, 1 day ago

On Fri, Mar 6, 2026 at 3:35 PM Rosen Penev <rosenp@gmail.com> wrote:
>
> The former is just a nice macro and the latter allows runtime analysis
> of the allocation and its size.
>
> Signed-off-by: Rosen Penev <rosenp@gmail.com>
Applied it to #ksmbd-for-next-next.
Thanks!