Hello,
syzbot found the following issue on:
HEAD commit: 483fed3b5dc8 Add linux-next specific files for 20220921
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1154ddd5080000
kernel config: https://syzkaller.appspot.com/x/.config?x=849cb9f70f15b1ba
dashboard link: https://syzkaller.appspot.com/bug?extid=473754e5af963cf014cf
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=157c196f080000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11f12618880000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1cb3f4618323/disk-483fed3b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cc02cb30b495/vmlinux-483fed3b.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]
------------[ cut here ]------------
memcpy: detected field-spanning write (size 8) of single field "&compat_event->pointer" at net/wireless/wext-core.c:623 (size 4)
WARNING: CPU: 0 PID: 3607 at net/wireless/wext-core.c:623 wireless_send_event+0xab5/0xca0 net/wireless/wext-core.c:623
Modules linked in:
CPU: 1 PID: 3607 Comm: syz-executor659 Not tainted 6.0.0-rc6-next-20220921-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2022
RIP: 0010:wireless_send_event+0xab5/0xca0 net/wireless/wext-core.c:623
Code: fa ff ff e8 cd b9 db f8 b9 04 00 00 00 4c 89 e6 48 c7 c2 e0 56 11 8b 48 c7 c7 20 56 11 8b c6 05 94 8e 2a 05 01 e8 b8 b0 a6 00 <0f> 0b e9 9b fa ff ff e8 6f ef 27 f9 e9 a6 fd ff ff e8 c5 ef 27 f9
RSP: 0018:ffffc90003b2fbc0 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888021d157c0 RSI: ffffffff81620348 RDI: fffff52000765f6a
RBP: ffff88801e15c780 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 20676e696e6e6170 R12: 0000000000000008
R13: ffff888025a72640 R14: ffff8880225d402c R15: ffff8880225d4034
FS: 0000555556bd9300(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbda677dfb8 CR3: 000000007b976000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ioctl_standard_call+0x155/0x1f0 net/wireless/wext-core.c:1022
wireless_process_ioctl+0xc8/0x4c0 net/wireless/wext-core.c:955
wext_ioctl_dispatch net/wireless/wext-core.c:988 [inline]
wext_ioctl_dispatch net/wireless/wext-core.c:976 [inline]
wext_handle_ioctl+0x26b/0x280 net/wireless/wext-core.c:1049
sock_ioctl+0x285/0x640 net/socket.c:1220
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fbda6736af9
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd45e80138 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fbda6736af9
RDX: 0000000020000000 RSI: 0000000000008b04 RDI: 0000000000000003
RBP: 00007fbda66faca0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fbda66fad30
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
---
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Syzkaller reports buffer overflow false positive as follows:
------------[ cut here ]------------
memcpy: detected field-spanning write (size 8) of single field
"&compat_event->pointer" at net/wireless/wext-core.c:623 (size 4)
WARNING: CPU: 0 PID: 3607 at net/wireless/wext-core.c:623
wireless_send_event+0xab5/0xca0 net/wireless/wext-core.c:623
Modules linked in:
CPU: 1 PID: 3607 Comm: syz-executor659 Not tainted
6.0.0-rc6-next-20220921-syzkaller #0
[...]
Call Trace:
<TASK>
ioctl_standard_call+0x155/0x1f0 net/wireless/wext-core.c:1022
wireless_process_ioctl+0xc8/0x4c0 net/wireless/wext-core.c:955
wext_ioctl_dispatch net/wireless/wext-core.c:988 [inline]
wext_ioctl_dispatch net/wireless/wext-core.c:976 [inline]
wext_handle_ioctl+0x26b/0x280 net/wireless/wext-core.c:1049
sock_ioctl+0x285/0x640 net/socket.c:1220
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline]
__se_sys_ioctl fs/ioctl.c:856 [inline]
__x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
[...]
</TASK>
Wireless events will be sent on the appropriate channels in
wireless_send_event(). Different wireless events may have different
payload structure and size, so kernel uses **len** and **cmd** field
in struct __compat_iw_event as wireless event common LCP part, uses
**pointer** as a label to mark the position of remaining different part.
Yet the problem is that, **pointer** is a compat_caddr_t type, which may
be smaller than the relative structure at the same position. So during
wireless_send_event() tries to parse the wireless events payload, it may
trigger the memcpy() run-time destination buffer bounds checking when the
relative structure's data is copied to the position marked by **pointer**.
This patch solves it by introducing flexible-array field **ptr_bytes**,
to mark the position of the wireless events remaining part next to
LCP part. What's more, this patch also adds **ptr_len** variable in
wireless_send_event() to improve its maintainability.
Reported-and-tested-by: [email protected]
Link: https://lore.kernel.org/all/[email protected]/
Suggested-by: Kees Cook <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Signed-off-by: Hawkins Jiawei <[email protected]>
---
v2: correct the typo error pointed out by Eric Dumazet and
Kees Cook
v1: https://lore.kernel.org/all/[email protected]/
include/linux/wireless.h | 10 +++++++++-
net/wireless/wext-core.c | 17 ++++++++++-------
2 files changed, 19 insertions(+), 8 deletions(-)
diff --git a/include/linux/wireless.h b/include/linux/wireless.h
index 2d1b54556eff..e6e34d74dda0 100644
--- a/include/linux/wireless.h
+++ b/include/linux/wireless.h
@@ -26,7 +26,15 @@ 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;
+
+ /* we need ptr_bytes to make memcpy() run-time destination
+ * buffer bounds checking happy, nothing special
+ */
+ 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..fe8765c4075d 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 +583,9 @@ 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 is remaining size in event header apart from LCP */
+ 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 +616,15 @@ 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,
- ((char *) &compat_wrqu) + IW_EV_COMPAT_POINT_OFF,
- hdr_len - IW_EV_COMPAT_LCP_LEN);
+ memcpy(compat_event->ptr_bytes,
+ ((char *)&compat_wrqu) + IW_EV_COMPAT_POINT_OFF,
+ ptr_len);
if (extra_len)
- memcpy(((char *) compat_event) + hdr_len,
- extra, extra_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);
--
2.25.1