hvc framework will never pass stack memory to the put_chars() function,
So the calling of kmemdup() is unnecessary, remove it.
Fixes: c4baad5029 ("virtio-console: avoid DMA from stack")
Signed-off-by: Xianting Tian <[email protected]>
---
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);
}
/*
--
2.17.1
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 <[email protected]>
> ---
> 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
On 02. 08. 21, 10:32, Xianting Tian wrote:
>
> 在 2021/8/2 下午3:25, Jiri Slaby 写道:
>> Hi,
>>
>> why is this 2/2? I seem (Lore neither) to find 1/2.
> You didn't receive 1/2?
> [PATCH 1/2] tty: hvc: pass DMA capable memory to put_chars()
> https://lkml.org/lkml/2021/8/1/8 <https://lkml.org/lkml/2021/8/1/8>
Oh, I did, but it's not properly threaded. PLease fix your setup.
>> 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.
>
> yes, I discussed the issue with Arnd before in below thread, you can
> get the history, thanks
>
> https://lkml.org/lkml/2021/7/27/494 <https://lkml.org/lkml/2021/7/27/494>
So is this a v2? You should have noted that. And what changed from v1 too.
>>> 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.
>
> yes, we discussed ther issue in above thread, which we CCed the author.
I don't see any input from the author?
Anyway, 1/2 does not even build, so you will send v3 with all the above
fixed, hopefully.
thanks,
--
js
在 2021/8/2 下午4:40, Jiri Slaby 写道:
> On 02. 08. 21, 10:32, Xianting Tian wrote:
>>
>> 在 2021/8/2 下午3:25, Jiri Slaby 写道:
>>> Hi,
>>>
>>> why is this 2/2? I seem (Lore neither) to find 1/2.
>> You didn't receive 1/2?
>> [PATCH 1/2] tty: hvc: pass DMA capable memory to put_chars()
>> https://lkml.org/lkml/2021/8/1/8 <https://lkml.org/lkml/2021/8/1/8>
>
> Oh, I did, but it's not properly threaded. PLease fix your setup.
Ok, thanks
>
>>> 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.
>>
>> yes, I discussed the issue with Arnd before in below thread, you can
>> get the history, thanks
>>
>> https://lkml.org/lkml/2021/7/27/494
>> <https://lkml.org/lkml/2021/7/27/494>
>
> So is this a v2? You should have noted that. And what changed from v1
> too.
I think yes, I should mentioned it in this patch, sorry for that:(
>
>>>> 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.
>>
>> yes, we discussed ther issue in above thread, which we CCed the author.
>
> I don't see any input from the author?
>
>
> Anyway, 1/2 does not even build, so you will send v3 with all the
> above fixed, hopefully.
yes, I will send v3 patch after I figured out a better solution based on
Arnd's comments for the patch '1/2'.
Do you have any other suggestion for the solution?
thanks.
>
> thanks,