2021-03-29 23:32:16

by Dmitry Safonov

Subject: [PATCH] xfrm/compat: Cleanup WARN()s that can be user-triggered

Replace WARN_ONCE() that can be triggered from userspace with
pr_warn_once(). Those still give user a hint what's the issue.

I've left WARN()s that are not possible to trigger with current
code-base and that would mean that the code has issues:
- relying on current compat_msg_min[type] <= xfrm_msg_min[type]
- expected 4-byte padding size difference between
compat_msg_min[type] and xfrm_msg_min[type]
- compat_policy[type].len <= xfrma_policy[type].len
(for every type)

Reported-by: [email protected]
Fixes: 5f3eea6b7e8f ("xfrm/compat: Attach xfrm dumps to 64=>32 bit translator")
Cc: "David S. Miller" <[email protected]>
Cc: Eric Dumazet <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Steffen Klassert <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Dmitry Safonov <[email protected]>
---
net/xfrm/xfrm_compat.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/net/xfrm/xfrm_compat.c b/net/xfrm/xfrm_compat.c
index d8e8a11ca845..a20aec9d7393 100644
--- a/net/xfrm/xfrm_compat.c
+++ b/net/xfrm/xfrm_compat.c
@@ -216,7 +216,7 @@ static struct nlmsghdr *xfrm_nlmsg_put_compat(struct sk_buff *skb,
case XFRM_MSG_GETSADINFO:
case XFRM_MSG_GETSPDINFO:
default:
- WARN_ONCE(1, "unsupported nlmsg_type %d", nlh_src->nlmsg_type);
+ pr_warn_once("unsupported nlmsg_type %d\n", nlh_src->nlmsg_type);
return ERR_PTR(-EOPNOTSUPP);
}

@@ -277,7 +277,7 @@ static int xfrm_xlate64_attr(struct sk_buff *dst, const struct nlattr *src)
return xfrm_nla_cpy(dst, src, nla_len(src));
default:
BUILD_BUG_ON(XFRMA_MAX != XFRMA_IF_ID);
- WARN_ONCE(1, "unsupported nla_type %d", src->nla_type);
+ pr_warn_once("unsupported nla_type %d\n", src->nla_type);
return -EOPNOTSUPP;
}
}
@@ -315,8 +315,10 @@ static int xfrm_alloc_compat(struct sk_buff *skb, const struct nlmsghdr *nlh_src
struct sk_buff *new = NULL;
int err;

- if (WARN_ON_ONCE(type >= ARRAY_SIZE(xfrm_msg_min)))
+ if (type >= ARRAY_SIZE(xfrm_msg_min)) {
+ pr_warn_once("unsupported nlmsg_type %d\n", nlh_src->nlmsg_type);
return -EOPNOTSUPP;
+ }

if (skb_shinfo(skb)->frag_list == NULL) {
new = alloc_skb(skb->len + skb_tailroom(skb), GFP_ATOMIC);
@@ -378,6 +380,10 @@ static int xfrm_attr_cpy32(void *dst, size_t *pos, const struct nlattr *src,
struct nlmsghdr *nlmsg = dst;
struct nlattr *nla;

+ /* xfrm_user_rcv_msg_compat() relies on fact that 32-bit messages
+ * have the same len or shorted than 64-bit ones.
+ * 32-bit translation that is bigger than 64-bit original is unexpected.
+ */
if (WARN_ON_ONCE(copy_len > payload))
copy_len = payload;

--
2.31.0

2021-03-31 07:46:23

by Steffen Klassert

Subject: Re: [PATCH] xfrm/compat: Cleanup WARN()s that can be user-triggered

On Tue, Mar 30, 2021 at 12:25:06AM +0100, Dmitry Safonov wrote:
> Replace WARN_ONCE() that can be triggered from userspace with
> pr_warn_once(). Those still give user a hint what's the issue.
>
> I've left WARN()s that are not possible to trigger with current
> code-base and that would mean that the code has issues:
> - relying on current compat_msg_min[type] <= xfrm_msg_min[type]
> - expected 4-byte padding size difference between
> compat_msg_min[type] and xfrm_msg_min[type]
> - compat_policy[type].len <= xfrma_policy[type].len
> (for every type)
>
> Reported-by: [email protected]
> Fixes: 5f3eea6b7e8f ("xfrm/compat: Attach xfrm dumps to 64=>32 bit translator")
> Cc: "David S. Miller" <[email protected]>
> Cc: Eric Dumazet <[email protected]>
> Cc: Herbert Xu <[email protected]>
> Cc: Jakub Kicinski <[email protected]>
> Cc: Steffen Klassert <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Dmitry Safonov <[email protected]>

Applied, thanks Dmitry!