[PATCH] net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()

[PATCH] net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()

[Sabyrzhan Tasbolatov]

syzbot found WARNING in qrtr_tun_write_iter [1] when write_iter length
exceeds KMALLOC_MAX_SIZE causing order >= MAX_ORDER condition.

Additionally, there is no check for 0 length write.

[1]
WARNING: mm/page_alloc.c:5011
[..]
Call Trace:
 alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267
 alloc_pages include/linux/gfp.h:547 [inline]
 kmalloc_order+0x2e/0xb0 mm/slab_common.c:837
 kmalloc_order_trace+0x14/0x120 mm/slab_common.c:853
 kmalloc include/linux/slab.h:557 [inline]
 kzalloc include/linux/slab.h:682 [inline]
 qrtr_tun_write_iter+0x8a/0x180 net/qrtr/tun.c:83
 call_write_iter include/linux/fs.h:1901 [inline]

Reported-by: syzbot+c2a7e5c5211605a90865@syzkaller.appspotmail.com
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
---
 net/qrtr/tun.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/qrtr/tun.c b/net/qrtr/tun.c
index 15ce9b642b25..b238c40a9984 100644
--- a/net/qrtr/tun.c
+++ b/net/qrtr/tun.c
@@ -80,6 +80,12 @@ static ssize_t qrtr_tun_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ssize_t ret;
 	void *kbuf;
 
+	if (!len)
+		return -EINVAL;
+
+	if (len > KMALLOC_MAX_SIZE)
+		return -ENOMEM;
+
 	kbuf = kzalloc(len, GFP_KERNEL);
 	if (!kbuf)
 		return -ENOMEM;
-- 
2.25.1

Re: [PATCH] net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()

[Jakub Kicinski]

On Tue,  2 Feb 2021 15:20:59 +0600 Sabyrzhan Tasbolatov wrote:
> syzbot found WARNING in qrtr_tun_write_iter [1] when write_iter length
> exceeds KMALLOC_MAX_SIZE causing order >= MAX_ORDER condition.
> 
> Additionally, there is no check for 0 length write.
> 
> [1]
> WARNING: mm/page_alloc.c:5011
> [..]
> Call Trace:
>  alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267
>  alloc_pages include/linux/gfp.h:547 [inline]
>  kmalloc_order+0x2e/0xb0 mm/slab_common.c:837
>  kmalloc_order_trace+0x14/0x120 mm/slab_common.c:853
>  kmalloc include/linux/slab.h:557 [inline]
>  kzalloc include/linux/slab.h:682 [inline]
>  qrtr_tun_write_iter+0x8a/0x180 net/qrtr/tun.c:83
>  call_write_iter include/linux/fs.h:1901 [inline]
> 
> Reported-by: syzbot+c2a7e5c5211605a90865@syzkaller.appspotmail.com
> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
> ---
>  net/qrtr/tun.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/net/qrtr/tun.c b/net/qrtr/tun.c
> index 15ce9b642b25..b238c40a9984 100644
> --- a/net/qrtr/tun.c
> +++ b/net/qrtr/tun.c
> @@ -80,6 +80,12 @@ static ssize_t qrtr_tun_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  	ssize_t ret;
>  	void *kbuf;
>  
> +	if (!len)
> +		return -EINVAL;
> +
> +	if (len > KMALLOC_MAX_SIZE)
> +		return -ENOMEM;
> +
>  	kbuf = kzalloc(len, GFP_KERNEL);

For potential, separate clean up - this is followed 
by copy_from_iter_full(len) kzalloc() can probably 
be replaced by kmalloc()?

>  	if (!kbuf)
>  		return -ENOMEM;

Re: [PATCH] net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (refs/heads/master):

On Tue,  2 Feb 2021 15:20:59 +0600 you wrote:
> syzbot found WARNING in qrtr_tun_write_iter [1] when write_iter length
> exceeds KMALLOC_MAX_SIZE causing order >= MAX_ORDER condition.
> 
> Additionally, there is no check for 0 length write.
> 
> [1]
> WARNING: mm/page_alloc.c:5011
> [..]
> Call Trace:
>  alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267
>  alloc_pages include/linux/gfp.h:547 [inline]
>  kmalloc_order+0x2e/0xb0 mm/slab_common.c:837
>  kmalloc_order_trace+0x14/0x120 mm/slab_common.c:853
>  kmalloc include/linux/slab.h:557 [inline]
>  kzalloc include/linux/slab.h:682 [inline]
>  qrtr_tun_write_iter+0x8a/0x180 net/qrtr/tun.c:83
>  call_write_iter include/linux/fs.h:1901 [inline]
> 
> [...]

Here is the summary with links:
  - net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()
    https://git.kernel.org/netdev/net/c/2a80c1581237

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

[PATCH] net/qrtr: replaced useless kzalloc with kmalloc in qrtr_tun_write_iter()

[Sabyrzhan Tasbolatov]

Replaced kzalloc() with kmalloc(), there is no need for zeroed-out
memory for simple void *kbuf.

>For potential, separate clean up - this is followed 
>by copy_from_iter_full(len) kzalloc() can probably 
>be replaced by kmalloc()?
>
>>  	if (!kbuf)
>>  		return -ENOMEM;

Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
---
 net/qrtr/tun.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/qrtr/tun.c b/net/qrtr/tun.c
index b238c40a9984..9b607c7614de 100644
--- a/net/qrtr/tun.c
+++ b/net/qrtr/tun.c
@@ -86,7 +86,7 @@ static ssize_t qrtr_tun_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	if (len > KMALLOC_MAX_SIZE)
 		return -ENOMEM;
 
-	kbuf = kzalloc(len, GFP_KERNEL);
+	kbuf = kmalloc(len, GFP_KERNEL);
 	if (!kbuf)
 		return -ENOMEM;
 
-- 
2.25.1

Re: [PATCH] net/qrtr: replaced useless kzalloc with kmalloc in qrtr_tun_write_iter()

[Jakub Kicinski]

On Thu,  4 Feb 2021 15:02:30 +0600 Sabyrzhan Tasbolatov wrote:
> Replaced kzalloc() with kmalloc(), there is no need for zeroed-out
> memory for simple void *kbuf.

There is no need for zeroed-out memory because it's immediately
overwritten by copy_from_iter...

> >For potential, separate clean up - this is followed 
> >by copy_from_iter_full(len) kzalloc() can probably 
> >be replaced by kmalloc()?
> >  
> >>  	if (!kbuf)
> >>  		return -ENOMEM;  
> 
> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
> ---
>  net/qrtr/tun.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/qrtr/tun.c b/net/qrtr/tun.c
> index b238c40a9984..9b607c7614de 100644
> --- a/net/qrtr/tun.c
> +++ b/net/qrtr/tun.c
> @@ -86,7 +86,7 @@ static ssize_t qrtr_tun_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  	if (len > KMALLOC_MAX_SIZE)
>  		return -ENOMEM;
>  
> -	kbuf = kzalloc(len, GFP_KERNEL);
> +	kbuf = kmalloc(len, GFP_KERNEL);
>  	if (!kbuf)
>  		return -ENOMEM;
>  

Re: [PATCH] net/qrtr: replaced useless kzalloc with kmalloc in qrtr_tun_write_iter()

[Jakub Kicinski]

On Thu, 4 Feb 2021 10:51:59 -0800 Jakub Kicinski wrote:
> On Thu,  4 Feb 2021 15:02:30 +0600 Sabyrzhan Tasbolatov wrote:
> > Replaced kzalloc() with kmalloc(), there is no need for zeroed-out
> > memory for simple void *kbuf.  
> 
> There is no need for zeroed-out memory because it's immediately
> overwritten by copy_from_iter...

Also if you don't mind please wait a week until the fixes get merged
back into net-next and then repost. Otherwise this patch will not apply
cleanly. (Fixes are merged into a different tree than cleanups)

> > Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
> > ---
> >  net/qrtr/tun.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/qrtr/tun.c b/net/qrtr/tun.c
> > index b238c40a9984..9b607c7614de 100644
> > --- a/net/qrtr/tun.c
> > +++ b/net/qrtr/tun.c
> > @@ -86,7 +86,7 @@ static ssize_t qrtr_tun_write_iter(struct kiocb *iocb, struct iov_iter *from)
> >  	if (len > KMALLOC_MAX_SIZE)
> >  		return -ENOMEM;
> >  
> > -	kbuf = kzalloc(len, GFP_KERNEL);
> > +	kbuf = kmalloc(len, GFP_KERNEL);
> >  	if (!kbuf)
> >  		return -ENOMEM;
> >    
> 

Re: [PATCH] net/qrtr: restrict user-controlled length in qrtr_tun_write_iter()

[Eric Dumazet]

On 2/2/21 10:20 AM, Sabyrzhan Tasbolatov wrote:
> syzbot found WARNING in qrtr_tun_write_iter [1] when write_iter length
> exceeds KMALLOC_MAX_SIZE causing order >= MAX_ORDER condition.
> 
> Additionally, there is no check for 0 length write.
> 
> [1]
> WARNING: mm/page_alloc.c:5011
> [..]
> Call Trace:
>  alloc_pages_current+0x18c/0x2a0 mm/mempolicy.c:2267
>  alloc_pages include/linux/gfp.h:547 [inline]
>  kmalloc_order+0x2e/0xb0 mm/slab_common.c:837
>  kmalloc_order_trace+0x14/0x120 mm/slab_common.c:853
>  kmalloc include/linux/slab.h:557 [inline]
>  kzalloc include/linux/slab.h:682 [inline]
>  qrtr_tun_write_iter+0x8a/0x180 net/qrtr/tun.c:83
>  call_write_iter include/linux/fs.h:1901 [inline]
> 
> Reported-by: syzbot+c2a7e5c5211605a90865@syzkaller.appspotmail.com
> Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@gmail.com>
> ---
>  net/qrtr/tun.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/net/qrtr/tun.c b/net/qrtr/tun.c
> index 15ce9b642b25..b238c40a9984 100644
> --- a/net/qrtr/tun.c
> +++ b/net/qrtr/tun.c
> @@ -80,6 +80,12 @@ static ssize_t qrtr_tun_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  	ssize_t ret;
>  	void *kbuf;
>  
> +	if (!len)
> +		return -EINVAL;
> +
> +	if (len > KMALLOC_MAX_SIZE)
> +		return -ENOMEM;



Probably not enough.

qrtr_endpoint_post() will later attempt a netdev_alloc_skb() which will need
some extra space (for struct skb_shared_info) 

Do we really expect to accept huge lengths here ?


> +
>  	kbuf = kzalloc(len, GFP_KERNEL);
>  	if (!kbuf)
>  		return -ENOMEM;
> 

Re: [PATCH] net/qrtr: restrict length in qrtr_tun_write_iter()

[Sabyrzhan Tasbolatov]

> Do we really expect to accept huge lengths here ?

Sorry for late response but I couldnt find any reference to the max
length of incoming data for qrtr TUN interface.

> qrtr_endpoint_post() will later attempt a netdev_alloc_skb() which will need
> some extra space (for struct skb_shared_info)

Thanks, you're right, qrtr_endpoint_post() will alloc another slab buffer.
We can check the length of skb allocation but we need to do following:

int qrtr_endpoint_post(.., const void *data, size_t len) 
{
	..
	when QRTR_PROTO_VER_1:
		hdrlen = sizeof(*data);
	when QRTR_PROTO_VER_2:
		hdrlen = sizeof(*data) + data->optlen;
	
	len = (KMALLOC_MAX_SIZE - hdrlen) % data->size;
	skb = netdev_alloc_skb(NULL, len);
	..
	skb_put_data(skb, data + hdrlen, size);


So it requires refactoring as in qrtr_tun_write_iter() we just allocate and
pass it to qrtr_endpoint_post() and there
we need to do len calculation as above *before* netdev_alloc_skb(NULL, len).

Perhaps there is a nicer solution though.

Re: [PATCH] net/qrtr: restrict length in qrtr_tun_write_iter()

[Eric Dumazet]

On 2/21/21 1:39 PM, Sabyrzhan Tasbolatov wrote:
>> Do we really expect to accept huge lengths here ?
> 
> Sorry for late response but I couldnt find any reference to the max
> length of incoming data for qrtr TUN interface.
> 
>> qrtr_endpoint_post() will later attempt a netdev_alloc_skb() which will need
>> some extra space (for struct skb_shared_info)
> 
> Thanks, you're right, qrtr_endpoint_post() will alloc another slab buffer.
> We can check the length of skb allocation but we need to do following:
> 
> int qrtr_endpoint_post(.., const void *data, size_t len) 
> {
> 	..
> 	when QRTR_PROTO_VER_1:
> 		hdrlen = sizeof(*data);
> 	when QRTR_PROTO_VER_2:
> 		hdrlen = sizeof(*data) + data->optlen;
> 	
> 	len = (KMALLOC_MAX_SIZE - hdrlen) % data->size;
> 	skb = netdev_alloc_skb(NULL, len);
> 	..
> 	skb_put_data(skb, data + hdrlen, size);
> 
> 
> So it requires refactoring as in qrtr_tun_write_iter() we just allocate and
> pass it to qrtr_endpoint_post() and there
> we need to do len calculation as above *before* netdev_alloc_skb(NULL, len).
> 
> Perhaps there is a nicer solution though.
> 

A protocol requiring contiguous physical memory allocations of up to KMALLOC_MAX_SIZE
bytes would be really unreliable.

I suggest we simply limit the allocations to 64KB, unless qrtr maintainers shout,
or start implementing scatter gather.