2023-01-10 10:27:38

by Anastasia Belova

Subject: [PATCH] xfrm: compat: change expression for switch in xfrm_xlate64

Compare XFRM_MSG_NEWSPDINFO (value from netlink
configuration messages enum) with nlh_src->nlmsg_type
instead of nlh_src->nlmsg_type - XFRM_MSG_BASE.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 4e9505064f58 ("net/xfrm/compat: Copy xfrm_spdattr_type_t atributes")
Signed-off-by: Anastasia Belova <[email protected]>
---
net/xfrm/xfrm_compat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_compat.c b/net/xfrm/xfrm_compat.c
index a0f62fa02e06..12405aa5bce8 100644
--- a/net/xfrm/xfrm_compat.c
+++ b/net/xfrm/xfrm_compat.c
@@ -302,7 +302,7 @@ static int xfrm_xlate64(struct sk_buff *dst, const struct nlmsghdr *nlh_src)
nla_for_each_attr(nla, attrs, len, remaining) {
int err;

- switch (type) {
+ switch (nlh_src->nlmsg_type) {
case XFRM_MSG_NEWSPDINFO:
err = xfrm_nla_cpy(dst, nla, nla_len(nla));
break;
--
2.30.2

2023-01-10 17:50:30

by Dmitry Safonov

Subject: Re: [PATCH] xfrm: compat: change expression for switch in xfrm_xlate64

On 1/10/23 09:14, Anastasia Belova wrote:
> Compare XFRM_MSG_NEWSPDINFO (value from netlink
> configuration messages enum) with nlh_src->nlmsg_type
> instead of nlh_src->nlmsg_type - XFRM_MSG_BASE.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.

Nice find!

Looking at the details:
xfrm_xlate64() is for translating 64-bit kernel-issued message to 32-bit
userspace ABI. The message is XFRM_MSG_NEWSPDINFO and there's a selftest
that checks if the attributes (thresh valued) were correctly translated
in tools/testing/selftests/net/ipsec.c

So, I was interested in how did it go unnoticed?
The switch here is to differ XFRMA_* attributes from XFRMA_SPD_*
attributes, which can be just copied as they are as they occupy the same
space on 64-bit as well as on 32-bit.

enum xfrm_spdattr_type_t {
XFRMA_SPD_UNSPEC,
XFRMA_SPD_INFO,
XFRMA_SPD_HINFO,
XFRMA_SPD_IPV4_HTHRESH,
XFRMA_SPD_IPV6_HTHRESH,
__XFRMA_SPD_MAX
};
attributes went through xfrm_xlate64_attr() instead of just being
copied. That worked in result as
case XFRMA_UNSPEC:
case XFRMA_ALG_AUTH:
case XFRMA_ALG_CRYPT:
case XFRMA_ALG_COMP:
case XFRMA_ENCAP:
case XFRMA_TMPL:
return xfrm_nla_cpy(dst, src, nla_len(src));
are equal by value (XFRMA_UNSPEC == 0 == XFRMA_SPD_UNSPEC) and so on.
So, in result, even with this typo the code worked.

What about the reverse case, what was being copied by this
XFRM_MSG_NEWSPDINFO case?
XFRM_MSG_NEWSPDINFO == 0x24
So, before this patch (XFRM_MSG_NEWSPDINFO - XFRM_MSG_BASE) == 0x14 ==
XFRM_MSG_DELPOLICY type of messages would fit this switch case.

Luckily enough, kernel doesn't send back XFRM_MSG_DELPOLICY messages to
userspace. That's how it went unnoticed, by unexpectedly still working.


> Fixes: 4e9505064f58 ("net/xfrm/compat: Copy xfrm_spdattr_type_t atributes")
> Signed-off-by: Anastasia Belova <[email protected]>

Thanks for the patch,
Acked-by: Dmitry Safonov <[email protected]>
Tested-by: Dmitry Safonov <[email protected]>

> ---
> net/xfrm/xfrm_compat.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/xfrm/xfrm_compat.c b/net/xfrm/xfrm_compat.c
> index a0f62fa02e06..12405aa5bce8 100644
> --- a/net/xfrm/xfrm_compat.c
> +++ b/net/xfrm/xfrm_compat.c
> @@ -302,7 +302,7 @@ static int xfrm_xlate64(struct sk_buff *dst, const struct nlmsghdr *nlh_src)
> nla_for_each_attr(nla, attrs, len, remaining) {
> int err;
>
> - switch (type) {
> + switch (nlh_src->nlmsg_type) {
> case XFRM_MSG_NEWSPDINFO:
> err = xfrm_nla_cpy(dst, nla, nla_len(nla));
> break;

2023-01-16 13:25:14

by Steffen Klassert

Subject: Re: [PATCH] xfrm: compat: change expression for switch in xfrm_xlate64

On Tue, Jan 10, 2023 at 12:14:50PM +0300, Anastasia Belova wrote:
> Compare XFRM_MSG_NEWSPDINFO (value from netlink
> configuration messages enum) with nlh_src->nlmsg_type
> instead of nlh_src->nlmsg_type - XFRM_MSG_BASE.
>
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>
> Fixes: 4e9505064f58 ("net/xfrm/compat: Copy xfrm_spdattr_type_t atributes")
> Signed-off-by: Anastasia Belova <[email protected]>

Applied, thanks a lot Anastasia!