Re: [PATCH 2/2] virtio-console: remove unnecessary kmemdup()

[Jiri Slaby]

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.t...@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);
  }
  
  /*



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