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SubjectRe: [PATCH 2/2] virtio-console: remove unnecessary kmemdup()
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Date
Hi,

why is this 2/2? I seem (Lore neither) to find 1/2.

On 01. 08. 21, 7:16, Xianting Tian wrote:
> hvc framework will never pass stack memory to the put_chars() function,

Am I blind or missing something?

hvc_console_print(...)
{
char c[N_OUTBUF]
...
cons_ops[index]->put_chars(vtermnos[index], c, i);

The same here:

hvc_poll_put_char(..., char ch)
{
...
n = hp->ops->put_chars(hp->vtermno, &ch, 1);

AFAICS both of them *pass* a pointer to stack variable.

> So the calling of kmemdup() is unnecessary, remove it.
>
> Fixes: c4baad5029 ("virtio-console: avoid DMA from stack")

This patch doesn't "Fix" -- it reverts the commit. You should've CCed
the author too.

> Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
> ---
> drivers/char/virtio_console.c | 12 ++----------
> 1 file changed, 2 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 7eaf303a7..4ed3ffb1d 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -1117,8 +1117,6 @@ static int put_chars(u32 vtermno, const char *buf, int count)
> {
> struct port *port;
> struct scatterlist sg[1];
> - void *data;
> - int ret;
>
> if (unlikely(early_put_chars))
> return early_put_chars(vtermno, buf, count);
> @@ -1127,14 +1125,8 @@ static int put_chars(u32 vtermno, const char *buf, int count)
> if (!port)
> return -EPIPE;
>
> - data = kmemdup(buf, count, GFP_ATOMIC);
> - if (!data)
> - return -ENOMEM;
> -
> - sg_init_one(sg, data, count);
> - ret = __send_to_port(port, sg, 1, count, data, false);
> - kfree(data);
> - return ret;
> + sg_init_one(sg, buf, count);
> + return __send_to_port(port, sg, 1, count, (void *)buf, false);
> }
>
> /*
>


--
js
suse labs

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