* Re: [PATCH 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2016-10-17 17:06 [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness() Andy Lutomirski
@ 2016-10-16 21:19 ` Matt Mullins
2016-10-17 17:17 ` [PATCH resend " Stephan Mueller
` (2 subsequent siblings)
3 siblings, 0 replies; 11+ messages in thread
From: Matt Mullins @ 2016-10-16 21:19 UTC (permalink / raw)
To: Andy Lutomirski; +Cc: Jens Axboe, Matt Mullins, linux-crypto
On Sun, Oct 16, 2016 at 10:17:15AM -0700, Andy Lutomirski wrote:
> hw_random carefully avoids using a stack buffer except in
> add_early_randomness(). This causes a crash in virtio_rng if
> CONFIG_VMAP_STACK=y.
I hadn't noticed the existing kmalloc in the __init, for the explicit purpose
of virt_to_page().
This boots on the VM from which I had grabbed the stack trace yesterday.
Tested-by: Matt Mullins <mmullins@mmlx.us>
Looks like an extra quote snuck in your To: line, so I'm not sure if this was
distributed as widely as you intended.
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2016-10-17 17:06 [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness() Andy Lutomirski
2016-10-16 21:19 ` [PATCH " Matt Mullins
@ 2016-10-17 17:17 ` Stephan Mueller
2016-10-17 17:30 ` Andy Lutomirski
2016-10-19 3:50 ` Herbert Xu
2017-02-04 3:47 ` Yisheng Xie
3 siblings, 1 reply; 11+ messages in thread
From: Stephan Mueller @ 2016-10-17 17:17 UTC (permalink / raw)
To: Andy Lutomirski
Cc: linux-crypto, linux-kernel, Matt Mackall, Herbert Xu,
Rusty Russell, Jens Axboe, Matt Mullins
Am Montag, 17. Oktober 2016, 10:06:27 CEST schrieb Andy Lutomirski:
Hi Andy,
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index 9203f2d130c0..340f96e44642 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -84,14 +84,14 @@ static size_t rng_buffer_size(void)
>
> static void add_early_randomness(struct hwrng *rng)
> {
> - unsigned char bytes[16];
> int bytes_read;
> + size_t size = min_t(size_t, 16, rng_buffer_size());
>
> mutex_lock(&reading_mutex);
> - bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
> + bytes_read = rng_get_data(rng, rng_buffer, size, 1);
> mutex_unlock(&reading_mutex);
> if (bytes_read > 0)
> - add_device_randomness(bytes, bytes_read);
> + add_device_randomness(rng_buffer, bytes_read);
Shouldn't there be a memset(0) of the rng_buffer at this point to avoid having
such data lingering in memory?
Ciao
Stephan
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2016-10-17 17:17 ` [PATCH resend " Stephan Mueller
@ 2016-10-17 17:30 ` Andy Lutomirski
2016-10-17 18:36 ` Stephan Mueller
0 siblings, 1 reply; 11+ messages in thread
From: Andy Lutomirski @ 2016-10-17 17:30 UTC (permalink / raw)
To: Stephan Mueller
Cc: Andy Lutomirski, linux-crypto, linux-kernel, Matt Mackall,
Herbert Xu, Rusty Russell, Jens Axboe, Matt Mullins
On Mon, Oct 17, 2016 at 10:17 AM, Stephan Mueller <smueller@chronox.de> wrote:
> Am Montag, 17. Oktober 2016, 10:06:27 CEST schrieb Andy Lutomirski:
>
> Hi Andy,
>
>> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
>> index 9203f2d130c0..340f96e44642 100644
>> --- a/drivers/char/hw_random/core.c
>> +++ b/drivers/char/hw_random/core.c
>> @@ -84,14 +84,14 @@ static size_t rng_buffer_size(void)
>>
>> static void add_early_randomness(struct hwrng *rng)
>> {
>> - unsigned char bytes[16];
>> int bytes_read;
>> + size_t size = min_t(size_t, 16, rng_buffer_size());
>>
>> mutex_lock(&reading_mutex);
>> - bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
>> + bytes_read = rng_get_data(rng, rng_buffer, size, 1);
>> mutex_unlock(&reading_mutex);
>> if (bytes_read > 0)
>> - add_device_randomness(bytes, bytes_read);
>> + add_device_randomness(rng_buffer, bytes_read);
>
> Shouldn't there be a memset(0) of the rng_buffer at this point to avoid having
> such data lingering in memory?
Sure, but shouldn't that be a separate patch covering the whole hw_crypto core?
--Andy
--
Andy Lutomirski
AMA Capital Management, LLC
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2016-10-17 17:30 ` Andy Lutomirski
@ 2016-10-17 18:36 ` Stephan Mueller
2016-10-17 21:03 ` Andy Lutomirski
0 siblings, 1 reply; 11+ messages in thread
From: Stephan Mueller @ 2016-10-17 18:36 UTC (permalink / raw)
To: Andy Lutomirski
Cc: Andy Lutomirski, linux-crypto, linux-kernel, Matt Mackall,
Herbert Xu, Rusty Russell, Jens Axboe, Matt Mullins
Am Montag, 17. Oktober 2016, 10:30:13 CEST schrieb Andy Lutomirski:
Hi Andy,
>
> Sure, but shouldn't that be a separate patch covering the whole hw_crypto
> core?
I think that you are right -- there are many more cases where a memset(0) is
warranted.
Do you want to make this change or should I send a patch?
Ciao
Stephan
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2016-10-17 18:36 ` Stephan Mueller
@ 2016-10-17 21:03 ` Andy Lutomirski
2016-10-17 21:14 ` Stephan Mueller
0 siblings, 1 reply; 11+ messages in thread
From: Andy Lutomirski @ 2016-10-17 21:03 UTC (permalink / raw)
To: Stephan Mueller
Cc: Andy Lutomirski, linux-crypto, linux-kernel, Matt Mackall,
Herbert Xu, Rusty Russell, Jens Axboe, Matt Mullins
On Mon, Oct 17, 2016 at 11:36 AM, Stephan Mueller <smueller@chronox.de> wrote:
> Am Montag, 17. Oktober 2016, 10:30:13 CEST schrieb Andy Lutomirski:
>
> Hi Andy,
>>
>> Sure, but shouldn't that be a separate patch covering the whole hw_crypto
>> core?
>
> I think that you are right -- there are many more cases where a memset(0) is
> warranted.
>
> Do you want to make this change or should I send a patch?
Can you do it? I have my work cut out for me making sure that all the
known regressions get stomped quickly...
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2016-10-17 21:03 ` Andy Lutomirski
@ 2016-10-17 21:14 ` Stephan Mueller
0 siblings, 0 replies; 11+ messages in thread
From: Stephan Mueller @ 2016-10-17 21:14 UTC (permalink / raw)
To: Andy Lutomirski
Cc: Andy Lutomirski, linux-crypto, linux-kernel, Matt Mackall,
Herbert Xu, Rusty Russell, Jens Axboe, Matt Mullins
Am Montag, 17. Oktober 2016, 14:03:17 CEST schrieb Andy Lutomirski:
Hi Andy,
> On Mon, Oct 17, 2016 at 11:36 AM, Stephan Mueller <smueller@chronox.de>
wrote:
> > Am Montag, 17. Oktober 2016, 10:30:13 CEST schrieb Andy Lutomirski:
> >
> > Hi Andy,
> >
> >> Sure, but shouldn't that be a separate patch covering the whole hw_crypto
> >> core?
> >
> > I think that you are right -- there are many more cases where a memset(0)
> > is warranted.
> >
> > Do you want to make this change or should I send a patch?
>
> Can you do it? I have my work cut out for me making sure that all the
> known regressions get stomped quickly...
Sure, will do.
Thanks.
Ciao
Stephan
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2016-10-17 17:06 [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness() Andy Lutomirski
2016-10-16 21:19 ` [PATCH " Matt Mullins
2016-10-17 17:17 ` [PATCH resend " Stephan Mueller
@ 2016-10-19 3:50 ` Herbert Xu
2017-02-04 3:47 ` Yisheng Xie
3 siblings, 0 replies; 11+ messages in thread
From: Herbert Xu @ 2016-10-19 3:50 UTC (permalink / raw)
To: Andy Lutomirski
Cc: linux-crypto, linux-kernel, Matt Mackall, Rusty Russell,
Jens Axboe, Matt Mullins
On Mon, Oct 17, 2016 at 10:06:27AM -0700, Andy Lutomirski wrote:
> hw_random carefully avoids using a stack buffer except in
> add_early_randomness(). This causes a crash in virtio_rng if
> CONFIG_VMAP_STACK=y.
>
> Reported-by: Matt Mullins <mmullins@mmlx.us>
> Tested-by: Matt Mullins <mmullins@mmlx.us>
> Fixes: d3cc7996473a ("hwrng: fetch randomness only after device init")
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
Patch applied. Thanks.
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2016-10-17 17:06 [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness() Andy Lutomirski
` (2 preceding siblings ...)
2016-10-19 3:50 ` Herbert Xu
@ 2017-02-04 3:47 ` Yisheng Xie
2017-02-04 4:34 ` Matt Mullins
3 siblings, 1 reply; 11+ messages in thread
From: Yisheng Xie @ 2017-02-04 3:47 UTC (permalink / raw)
To: Andy Lutomirski, linux-crypto, linux-kernel, Matt Mackall,
Herbert Xu, Rusty Russell
Cc: Jens Axboe, Matt Mullins, Xishi Qiu, Hanjun Guo
Hi Andy,
On 2016/10/18 1:06, Andy Lutomirski wrote:
> hw_random carefully avoids using a stack buffer except in
> add_early_randomness(). This causes a crash in virtio_rng if
> CONFIG_VMAP_STACK=y.
I try to understand this patch, but I do not know why it will cause
a crash in virtio_rng with CONFIG_VMAP_STACK=y?
Could you please give me more info. about it.
Really thanks for that!
Yisheng Xie.
>
> Reported-by: Matt Mullins <mmullins@mmlx.us>
> Tested-by: Matt Mullins <mmullins@mmlx.us>
> Fixes: d3cc7996473a ("hwrng: fetch randomness only after device init")
> Signed-off-by: Andy Lutomirski <luto@kernel.org>
> ---
>
> This fixes a crash in 4.9-rc1.
>
> resending because I typoed the git send-email command. I stealthily added
> Matt's Tested-by, too.
>
> drivers/char/hw_random/core.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index 9203f2d130c0..340f96e44642 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -84,14 +84,14 @@ static size_t rng_buffer_size(void)
>
> static void add_early_randomness(struct hwrng *rng)
> {
> - unsigned char bytes[16];
> int bytes_read;
> + size_t size = min_t(size_t, 16, rng_buffer_size());
>
> mutex_lock(&reading_mutex);
> - bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
> + bytes_read = rng_get_data(rng, rng_buffer, size, 1);
> mutex_unlock(&reading_mutex);
> if (bytes_read > 0)
> - add_device_randomness(bytes, bytes_read);
> + add_device_randomness(rng_buffer, bytes_read);
> }
>
> static inline void cleanup_rng(struct kref *kref)
>
^ permalink raw reply [flat|nested] 11+ messages in thread* Re: [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2017-02-04 3:47 ` Yisheng Xie
@ 2017-02-04 4:34 ` Matt Mullins
2017-02-04 10:32 ` Yisheng Xie
0 siblings, 1 reply; 11+ messages in thread
From: Matt Mullins @ 2017-02-04 4:34 UTC (permalink / raw)
To: Yisheng Xie
Cc: Andy Lutomirski, linux-crypto, linux-kernel, Matt Mackall,
Herbert Xu, Rusty Russell, Jens Axboe, Matt Mullins, Xishi Qiu,
Hanjun Guo
On Sat, Feb 04, 2017 at 11:47:38AM +0800, Yisheng Xie wrote:
> On 2016/10/18 1:06, Andy Lutomirski wrote:
> > hw_random carefully avoids using a stack buffer except in
> > add_early_randomness(). This causes a crash in virtio_rng if
> > CONFIG_VMAP_STACK=y.
> I try to understand this patch, but I do not know why it will cause
> a crash in virtio_rng with CONFIG_VMAP_STACK=y?
> Could you please give me more info. about it.
My original report was
https://lkml.kernel.org/r/20161016002151.GA18235@hydra.tuxags.com.
The virtio ring APIs use scatterlists to keep track of the buffers, and
scatterlist requires addresses to be in the kernel direct-mapped address range.
This is not the case for vmalloc()ed addresses, such as the original on-stack
"bytes" array when VMAP_STACK=y.
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH resend 4.9] hw_random: Don't use a stack buffer in add_early_randomness()
2017-02-04 4:34 ` Matt Mullins
@ 2017-02-04 10:32 ` Yisheng Xie
0 siblings, 0 replies; 11+ messages in thread
From: Yisheng Xie @ 2017-02-04 10:32 UTC (permalink / raw)
To: Andy Lutomirski, linux-crypto, linux-kernel, Matt Mackall,
Herbert Xu, Rusty Russell, Jens Axboe, Matt Mullins, Xishi Qiu,
Hanjun Guo
hi, Matt,
Thanks for your reply.
On 2017/2/4 12:34, Matt Mullins wrote:
> On Sat, Feb 04, 2017 at 11:47:38AM +0800, Yisheng Xie wrote:
>> On 2016/10/18 1:06, Andy Lutomirski wrote:
>>> hw_random carefully avoids using a stack buffer except in
>>> add_early_randomness(). This causes a crash in virtio_rng if
>>> CONFIG_VMAP_STACK=y.
>> I try to understand this patch, but I do not know why it will cause
>> a crash in virtio_rng with CONFIG_VMAP_STACK=y?
>> Could you please give me more info. about it.
>
> My original report was
> https://lkml.kernel.org/r/20161016002151.GA18235@hydra.tuxags.com.
>
> The virtio ring APIs use scatterlists to keep track of the buffers, and
> scatterlist requires addresses to be in the kernel direct-mapped address range.
> This is not the case for vmalloc()ed addresses, such as the original on-stack
> "bytes" array when VMAP_STACK=y.
>
I see, and will check the logic to get more detail about it.
Thanks.
Yisheng Xie
^ permalink raw reply [flat|nested] 11+ messages in thread