* [PATCH 2/2] virtio-console: remove unnecessary kmemdup() @ 2021-08-01 5:16 Xianting Tian 2021-08-02 7:25 ` Jiri Slaby 0 siblings, 1 reply; 5+ messages in thread From: Xianting Tian @ 2021-08-01 5:16 UTC (permalink / raw) To: gregkh, jirislaby, amit, arnd Cc: Xianting Tian, linuxppc-dev, linux-kernel, virtualization 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 <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); } /* -- 2.17.1 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] virtio-console: remove unnecessary kmemdup() 2021-08-01 5:16 [PATCH 2/2] virtio-console: remove unnecessary kmemdup() Xianting Tian @ 2021-08-02 7:25 ` Jiri Slaby 2021-08-02 8:32 ` Xianting Tian 0 siblings, 1 reply; 5+ messages in thread From: Jiri Slaby @ 2021-08-02 7:25 UTC (permalink / raw) To: Xianting Tian, gregkh, amit, arnd Cc: osandov, linuxppc-dev, linux-kernel, virtualization 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] virtio-console: remove unnecessary kmemdup() 2021-08-02 7:25 ` Jiri Slaby @ 2021-08-02 8:32 ` Xianting Tian 2021-08-02 8:40 ` Jiri Slaby 0 siblings, 1 reply; 5+ messages in thread From: Xianting Tian @ 2021-08-02 8:32 UTC (permalink / raw) To: Jiri Slaby, gregkh, amit, arnd Cc: osandov, linuxppc-dev, linux-kernel, virtualization [-- Attachment #1: Type: text/plain, Size: 2454 bytes --] 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> > > 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 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. > >> 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); >> } >> /* >> > > [-- Attachment #2: Type: text/html, Size: 4975 bytes --] ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] virtio-console: remove unnecessary kmemdup() 2021-08-02 8:32 ` Xianting Tian @ 2021-08-02 8:40 ` Jiri Slaby 2021-08-02 8:55 ` Xianting Tian 0 siblings, 1 reply; 5+ messages in thread From: Jiri Slaby @ 2021-08-02 8:40 UTC (permalink / raw) To: Xianting Tian, gregkh, amit, arnd Cc: osandov, linuxppc-dev, linux-kernel, virtualization 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 2/2] virtio-console: remove unnecessary kmemdup() 2021-08-02 8:40 ` Jiri Slaby @ 2021-08-02 8:55 ` Xianting Tian 0 siblings, 0 replies; 5+ messages in thread From: Xianting Tian @ 2021-08-02 8:55 UTC (permalink / raw) To: Jiri Slaby, gregkh, amit, arnd Cc: osandov, linuxppc-dev, linux-kernel, virtualization 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, ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2021-08-02 23:38 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-08-01 5:16 [PATCH 2/2] virtio-console: remove unnecessary kmemdup() Xianting Tian 2021-08-02 7:25 ` Jiri Slaby 2021-08-02 8:32 ` Xianting Tian 2021-08-02 8:40 ` Jiri Slaby 2021-08-02 8:55 ` Xianting Tian
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