[Linux-kernel-mentees] [PATCH net] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Linux-kernel-mentees] [PATCH net] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Peilin Ye]

xsk_getsockopt() is copying uninitialized stack memory to userspace when
`extra_stats` is `false`. Fix it by initializing `stats` with memset().

Cc: stable@vger.kernel.org
Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
 net/xdp/xsk.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 26e3bba8c204..acf001908a0d 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -844,6 +844,8 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
 		bool extra_stats = true;
 		size_t stats_size;
 
+		memset(&stats, 0, sizeof(stats));
+
 		if (len < sizeof(struct xdp_statistics_v1)) {
 			return -EINVAL;
 		} else if (len < sizeof(stats)) {
-- 
2.25.1

Re: [Linux-kernel-mentees] [PATCH net] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Song Liu]

On Mon, Jul 27, 2020 at 7:30 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>
> xsk_getsockopt() is copying uninitialized stack memory to userspace when
> `extra_stats` is `false`. Fix it by initializing `stats` with memset().
>
> Cc: stable@vger.kernel.org

8aa5a33578e9 is not in stable branches yet, so we don't need to Cc stable.

> Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> ---
>  net/xdp/xsk.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 26e3bba8c204..acf001908a0d 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -844,6 +844,8 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
>                 bool extra_stats = true;
>                 size_t stats_size;
>
> +               memset(&stats, 0, sizeof(stats));
> +

xsk.c doesn't include linux/string.h directly, so using memset may break
build for some config combinations. We can probably just use

struct xdp_statistics stats = {};

Thanks,
Song


>                 if (len < sizeof(struct xdp_statistics_v1)) {
>                         return -EINVAL;
>                 } else if (len < sizeof(stats)) {
> --
> 2.25.1
>

Re: [Linux-kernel-mentees] [PATCH net] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Peilin Ye]

On Mon, Jul 27, 2020 at 10:07:20PM -0700, Song Liu wrote:
> On Mon, Jul 27, 2020 at 7:30 PM Peilin Ye <yepeilin.cs@gmail.com> wrote:
> >
> > xsk_getsockopt() is copying uninitialized stack memory to userspace when
> > `extra_stats` is `false`. Fix it by initializing `stats` with memset().
> >
> > Cc: stable@vger.kernel.org
> 
> 8aa5a33578e9 is not in stable branches yet, so we don't need to Cc stable.
> 
> > Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
> > Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> > Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> > ---
> >  net/xdp/xsk.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> > index 26e3bba8c204..acf001908a0d 100644
> > --- a/net/xdp/xsk.c
> > +++ b/net/xdp/xsk.c
> > @@ -844,6 +844,8 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
> >                 bool extra_stats = true;
> >                 size_t stats_size;
> >
> > +               memset(&stats, 0, sizeof(stats));
> > +
> 
> xsk.c doesn't include linux/string.h directly, so using memset may break
> build for some config combinations. We can probably just use
> 
> struct xdp_statistics stats = {};

I see. I will send v2 soon. Thank you for reviewing the patch!

Peilin Ye

[Linux-kernel-mentees] [PATCH net v2] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Peilin Ye]

xsk_getsockopt() is copying uninitialized stack memory to userspace when
`extra_stats` is `false`. Fix it.

Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
Doing `= {};` is sufficient since currently `struct xdp_statistics` is
defined as follows:

struct xdp_statistics {
	__u64 rx_dropped;
	__u64 rx_invalid_descs;
	__u64 tx_invalid_descs;
	__u64 rx_ring_full;
	__u64 rx_fill_ring_empty_descs;
	__u64 tx_ring_empty_descs;
};

When being copied to the userspace, `stats` will not contain any
uninitialized "holes" between struct fields.

Changes in v2:
    - Remove the "Cc: stable@vger.kernel.org" tag. (Suggested by Song Liu
      <songliubraving@fb.com>)
    - Initialize `stats` by assignment instead of using memset().
      (Suggested by Song Liu <songliubraving@fb.com>)

 net/xdp/xsk.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 26e3bba8c204..b2b533eddebf 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -840,7 +840,7 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
 	switch (optname) {
 	case XDP_STATISTICS:
 	{
-		struct xdp_statistics stats;
+		struct xdp_statistics stats = {};
 		bool extra_stats = true;
 		size_t stats_size;
 
-- 
2.25.1

Re: [Linux-kernel-mentees] [PATCH net v2] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Björn Töpel]

On Tue, 28 Jul 2020 at 07:37, Peilin Ye <yepeilin.cs@gmail.com> wrote:
>
> xsk_getsockopt() is copying uninitialized stack memory to userspace when
> `extra_stats` is `false`. Fix it.
>
> Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> ---

Acked-by: Björn Töpel <bjorn.topel@intel.com>

> Doing `= {};` is sufficient since currently `struct xdp_statistics` is
> defined as follows:
>
> struct xdp_statistics {
>         __u64 rx_dropped;
>         __u64 rx_invalid_descs;
>         __u64 tx_invalid_descs;
>         __u64 rx_ring_full;
>         __u64 rx_fill_ring_empty_descs;
>         __u64 tx_ring_empty_descs;
> };
>
> When being copied to the userspace, `stats` will not contain any
> uninitialized "holes" between struct fields.
>
> Changes in v2:
>     - Remove the "Cc: stable@vger.kernel.org" tag. (Suggested by Song Liu
>       <songliubraving@fb.com>)
>     - Initialize `stats` by assignment instead of using memset().
>       (Suggested by Song Liu <songliubraving@fb.com>)
>
>  net/xdp/xsk.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 26e3bba8c204..b2b533eddebf 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -840,7 +840,7 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
>         switch (optname) {
>         case XDP_STATISTICS:
>         {
> -               struct xdp_statistics stats;
> +               struct xdp_statistics stats = {};
>                 bool extra_stats = true;
>                 size_t stats_size;
>
> --
> 2.25.1
>

Re: [Linux-kernel-mentees] [PATCH net v2] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Song Liu]

> On Jul 27, 2020, at 11:13 PM, Björn Töpel <bjorn.topel@gmail.com> wrote:
> 
> On Tue, 28 Jul 2020 at 07:37, Peilin Ye <yepeilin.cs@gmail.com> wrote:
>> 
>> xsk_getsockopt() is copying uninitialized stack memory to userspace when
>> `extra_stats` is `false`. Fix it.
>> 
>> Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
>> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
>> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
>> ---
> 
> Acked-by: Björn Töpel <bjorn.topel@intel.com>

Acked-by: Song Liu <songliubraving@fb.com>

[...]

Re: [Linux-kernel-mentees] [PATCH net v2] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Arnd Bergmann]

On Tue, Jul 28, 2020 at 7:37 AM Peilin Ye <yepeilin.cs@gmail.com> wrote:
>
> xsk_getsockopt() is copying uninitialized stack memory to userspace when
> `extra_stats` is `false`. Fix it.
>
> Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>

Acked-by: Arnd Bergmann <arnd@arndb.de>

Re: [Linux-kernel-mentees] [PATCH net v2] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Daniel Borkmann]

On 7/28/20 7:36 AM, Peilin Ye wrote:
> xsk_getsockopt() is copying uninitialized stack memory to userspace when
> `extra_stats` is `false`. Fix it.
> 
> Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> ---
> Doing `= {};` is sufficient since currently `struct xdp_statistics` is
> defined as follows:
> 
> struct xdp_statistics {
> 	__u64 rx_dropped;
> 	__u64 rx_invalid_descs;
> 	__u64 tx_invalid_descs;
> 	__u64 rx_ring_full;
> 	__u64 rx_fill_ring_empty_descs;
> 	__u64 tx_ring_empty_descs;
> };
> 
> When being copied to the userspace, `stats` will not contain any
> uninitialized "holes" between struct fields.

I've added above explanation to the commit log since it's useful reasoning for later
on 'why' something has been done a certain way. Applied, thanks Peilin!

Re: [Linux-kernel-mentees] [PATCH net v2] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Peilin Ye]

On Tue, Jul 28, 2020 at 12:53:59PM +0200, Daniel Borkmann wrote:
> On 7/28/20 7:36 AM, Peilin Ye wrote:
> > xsk_getsockopt() is copying uninitialized stack memory to userspace when
> > `extra_stats` is `false`. Fix it.
> > 
> > Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
> > Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
> > Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
> > ---
> > Doing `= {};` is sufficient since currently `struct xdp_statistics` is
> > defined as follows:
> > 
> > struct xdp_statistics {
> > 	__u64 rx_dropped;
> > 	__u64 rx_invalid_descs;
> > 	__u64 tx_invalid_descs;
> > 	__u64 rx_ring_full;
> > 	__u64 rx_fill_ring_empty_descs;
> > 	__u64 tx_ring_empty_descs;
> > };
> > 
> > When being copied to the userspace, `stats` will not contain any
> > uninitialized "holes" between struct fields.
> 
> I've added above explanation to the commit log since it's useful reasoning for later
> on 'why' something has been done a certain way. Applied, thanks Peilin!

Ah, I see. Thank you for reviewing the patch!

Peilin Ye