From: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> > 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: syzbot+473754e5af963cf014cf@xxxxxxxxxxxxxxxxxxxxxxxxx > > ------------[ 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> I think this is the samiliar problem as what Kees Cook pointed out in https://lore.kernel.org/linux-next/202209211250.3049C29@keescook/ It seems that memcpy() will performs run-time buffer bounds checking, which triggers this warning. #syz test git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master diff --git a/include/linux/wireless.h b/include/linux/wireless.h index 2d1b54556eff..81603848b0aa 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, pointer_flex); + }; }; #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..9d0b50abbe09 100644 --- a/net/wireless/wext-core.c +++ b/net/wireless/wext-core.c @@ -620,7 +620,7 @@ void wireless_send_event(struct net_device * dev, extra, extra_len); } else { /* extra_len must be zero, so no if (extra) needed */ - memcpy(&compat_event->pointer, wrqu, + memcpy(&compat_event->pointer_flex, wrqu, hdr_len - IW_EV_COMPAT_LCP_LEN); }
