syzbot


BUG: bad usercopy in put_cmsg

Status: fixed on 2023/06/08 14:41
Subsystems: hardening mm
[Documentation on labels]
Fix commit: 2558b8039d05 net: use a bounce buffer for copying skb->mark
First crash: 462d, last: 460d

Sample crash report:
usercopy: Kernel memory exposure attempt detected from SLUB object 'skbuff_head_cache' (offset 168, size 4)!
------------[ cut here ]------------
kernel BUG at mm/usercopy.c:102!
Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 4410 Comm: syz-executor533 Not tainted 6.2.0-rc7-syzkaller-17907-g2d3827b3f393 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : usercopy_abort+0x90/0x94 mm/usercopy.c:90
lr : usercopy_abort+0x90/0x94 mm/usercopy.c:90
sp : ffff80000fb9b9a0
x29: ffff80000fb9b9b0 x28: ffff0000c6073400 x27: 0000000020001a00
x26: 0000000000000014 x25: ffff80000cf52000 x24: fffffc0000000000
x23: 05ffc00000000200 x22: fffffc000324bf80 x21: ffff0000c92fe1a8
x20: 0000000000000001 x19: 0000000000000004 x18: 0000000000000000
x17: 656a626f2042554c x16: ffff0000c6073dd0 x15: ffff80000dbd2118
x14: ffff0000c6073400 x13: 00000000ffffffff x12: ffff0000c6073400
x11: ff808000081bbb4c x10: 0000000000000000 x9 : 7b0572d7cc0ccf00
x8 : 7b0572d7cc0ccf00 x7 : ffff80000bf650d4 x6 : 0000000000000000
x5 : 0000000000000001 x4 : 0000000000000001 x3 : 0000000000000000
x2 : ffff0001fefbff08 x1 : 0000000100000000 x0 : 000000000000006c
Call trace:
 usercopy_abort+0x90/0x94 mm/usercopy.c:90
 __check_heap_object+0xa8/0x100 mm/slub.c:4761
 check_heap_object mm/usercopy.c:196 [inline]
 __check_object_size+0x208/0x6b8 mm/usercopy.c:251
 check_object_size include/linux/thread_info.h:199 [inline]
 __copy_to_user include/linux/uaccess.h:115 [inline]
 put_cmsg+0x408/0x464 net/core/scm.c:238
 sock_recv_mark net/socket.c:975 [inline]
 __sock_recv_cmsgs+0x1fc/0x248 net/socket.c:984
 sock_recv_cmsgs include/net/sock.h:2728 [inline]
 packet_recvmsg+0x2d8/0x678 net/packet/af_packet.c:3482
 ____sys_recvmsg+0x110/0x3a0
 ___sys_recvmsg net/socket.c:2737 [inline]
 __sys_recvmsg+0x194/0x210 net/socket.c:2767
 __do_sys_recvmsg net/socket.c:2777 [inline]
 __se_sys_recvmsg net/socket.c:2774 [inline]
 __arm64_sys_recvmsg+0x2c/0x3c net/socket.c:2774
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x64/0x178 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0xbc/0x180 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x110 arch/arm64/kernel/syscall.c:193
 el0_svc+0x58/0x14c arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591
Code: 91388800 aa0903e1 f90003e8 94e6d752 (d4210000) 
---[ end trace 0000000000000000 ]---

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/02/12 08:11 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 2d3827b3f393 93e26d60 .config console log report syz C [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: bad usercopy in put_cmsg
2023/02/13 15:52 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 2d3827b3f393 4d66ad72 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: bad usercopy in put_cmsg
2023/02/12 07:52 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 2d3827b3f393 93e26d60 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 BUG: bad usercopy in put_cmsg
* Struck through repros no longer work on HEAD.