From: Kees Cook <keescook@chromium.org>
To: Hawkins Jiawei <yin31149@gmail.com>
Cc: 18801353760@163.com, davem@davemloft.net, edumazet@google.com,
johannes@sipsolutions.net, kuba@kernel.org,
linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org,
netdev@vger.kernel.org, pabeni@redhat.com, sfr@canb.auug.org.au,
syzbot+473754e5af963cf014cf@syzkaller.appspotmail.com,
syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH] Add linux-next specific files for 20220923
Date: Sat, 24 Sep 2022 09:26:01 -0700 [thread overview]
Message-ID: <202209240905.F5654D7A5@keescook> (raw)
In-Reply-To: <20220924155514.32408-1-yin31149@gmail.com>
On Sat, Sep 24, 2022 at 11:55:14PM +0800, Hawkins Jiawei wrote:
> > And as for the value of offsetof in calculating **offset**,
> > I wonder if we can use the macro defined in
> > include/linux/wireless.h as below, which makes code simplier:
> > #define IW_EV_COMPAT_LCP_LEN offsetof(struct __compat_iw_event, pointer)
Ah yes, that would be good.
> According to above code, it seems that kernel will saves enough memory
> (hdr_len + extra_len bytes) for payload structure in
> nla_reserve()(Please correct me if I am wrong), pointed by compat_event.
> So I wonder if we can use unsafe_memcpy(), to avoid unnecessary
> memcpy() check as below, which seems more simple:
I'd rather this was properly resolved with the creation of a real
flexible array so that when bounds tracking gets improved in the future,
the compiler can reason about it better. And, I think, it makes the code
more readable:
diff --git a/include/linux/wireless.h b/include/linux/wireless.h
index 2d1b54556eff..e0b4b46da63f 100644
--- a/include/linux/wireless.h
+++ b/include/linux/wireless.h
@@ -26,7 +26,10 @@ struct compat_iw_point {
struct __compat_iw_event {
__u16 len; /* Real length of this stuff */
__u16 cmd; /* Wireless IOCTL */
- compat_caddr_t pointer;
+ union {
+ compat_caddr_t pointer;
+ DECLARE_FLEX_ARRAY(__u8, ptr_bytes);
+ };
};
#define IW_EV_COMPAT_LCP_LEN offsetof(struct __compat_iw_event, pointer)
#define IW_EV_COMPAT_POINT_OFF offsetof(struct compat_iw_point, length)
diff --git a/net/wireless/wext-core.c b/net/wireless/wext-core.c
index 76a80a41615b..6079c8f4b634 100644
--- a/net/wireless/wext-core.c
+++ b/net/wireless/wext-core.c
@@ -468,6 +468,7 @@ void wireless_send_event(struct net_device * dev,
struct __compat_iw_event *compat_event;
struct compat_iw_point compat_wrqu;
struct sk_buff *compskb;
+ int ptr_len;
#endif
/*
@@ -582,6 +583,7 @@ void wireless_send_event(struct net_device * dev,
nlmsg_end(skb, nlh);
#ifdef CONFIG_COMPAT
hdr_len = compat_event_type_size[descr->header_type];
+ ptr_len = hdr_len - IW_EV_COMPAT_LCP_LEN;
event_len = hdr_len + extra_len;
compskb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
@@ -612,16 +614,15 @@ void wireless_send_event(struct net_device * dev,
if (descr->header_type == IW_HEADER_TYPE_POINT) {
compat_wrqu.length = wrqu->data.length;
compat_wrqu.flags = wrqu->data.flags;
- memcpy(&compat_event->pointer,
+ memcpy(compat_event->ptr_bytes,
((char *) &compat_wrqu) + IW_EV_COMPAT_POINT_OFF,
- hdr_len - IW_EV_COMPAT_LCP_LEN);
+ ptr_len);
if (extra_len)
- memcpy(((char *) compat_event) + hdr_len,
+ memcpy(compat_event->ptr_bytes + ptr_len,
extra, extra_len);
} else {
/* extra_len must be zero, so no if (extra) needed */
- memcpy(&compat_event->pointer, wrqu,
- hdr_len - IW_EV_COMPAT_LCP_LEN);
+ memcpy(compat_event->ptr_bytes, wrqu, ptr_len);
}
nlmsg_end(compskb, nlh);
--
Kees Cook
next prev parent reply other threads:[~2022-09-24 16:26 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-23 16:05 [syzbot] WARNING in wireless_send_event syzbot
2022-09-24 7:10 ` [PATCH] Add linux-next specific files for 20220923 Hawkins Jiawei
2022-09-24 7:26 ` Kees Cook
2022-09-24 11:44 ` Hawkins Jiawei
2022-09-24 15:55 ` Hawkins Jiawei
2022-09-24 15:55 ` syzbot
2022-09-24 16:13 ` Hawkins Jiawei
2022-09-24 16:33 ` [syzbot] WARNING in wireless_send_event syzbot
2022-09-24 16:26 ` Kees Cook [this message]
2022-09-25 6:25 ` [PATCH] Add linux-next specific files for 20220923 Hawkins Jiawei
2022-09-24 7:32 ` [syzbot] WARNING in wireless_send_event syzbot
2022-09-26 11:59 ` Hawkins Jiawei
2022-09-26 12:24 ` syzbot
2022-09-26 15:09 ` [PATCH] wext: use flex array destination for memcpy() Hawkins Jiawei
2022-09-26 16:14 ` Eric Dumazet
2022-09-26 23:17 ` Hawkins Jiawei
2022-09-26 17:43 ` Kees Cook
2022-09-26 23:34 ` [PATCH wireless-next v2] " Hawkins Jiawei
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