On Tue, Dec 19, 2017 at 4:57 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: >>> <bot+5e56fb40e0f2bc3f20402f782f0b3913cb959acc@xxxxxxxxxxxxxxxxxxxxxxxxx> >>> wrote: >>>> Hello, >>>> >>>> syzkaller hit the following crash on >>>> 6084b576dca2e898f5c101baef151f7bfdbb606d >>>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master >>>> compiler: gcc (GCC) 7.1.1 20170620 >>>> .config is attached >>>> Raw console output is attached. >>>> >>>> Unfortunately, I don't have any reproducer for this bug yet. >>>> >>>> >>>> device gre0 entered promiscuous mode >>>> usercopy: kernel memory exposure attempt detected from 00000000a6830059 >>>> (kmalloc-1024) (1024 bytes) >>>> ------------[ cut here ]------------ >>>> kernel BUG at mm/usercopy.c:84! >>>> invalid opcode: 0000 [#1] SMP >>>> Dumping ftrace buffer: >>>> (ftrace buffer empty) >>>> Modules linked in: >>>> CPU: 1 PID: 28799 Comm: syz-executor4 Not tainted 4.15.0-rc3-next-20171214+ >>>> #67 >>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS >>>> Google 01/01/2011 >>>> RIP: 0010:report_usercopy mm/usercopy.c:76 [inline] >>>> RIP: 0010:__check_object_size+0x1e2/0x250 mm/usercopy.c:276 >>>> RSP: 0018:ffffc9000116fc50 EFLAGS: 00010286 >>>> RAX: 0000000000000063 RBX: ffffffff82e6518f RCX: ffffffff8123dede >>>> RDX: 0000000000004c58 RSI: ffffc900050ed000 RDI: ffff88021fd136f8 >>>> RBP: ffffc9000116fc88 R08: 0000000000000000 R09: 0000000000000000 >>>> R10: 0000000000000000 R11: 0000000000000000 R12: ffff880216bb6050 >>>> R13: 0000000000000400 R14: 0000000000000001 R15: ffffffff82eda864 >>>> FS: 00007f61a06bc700(0000) GS:ffff88021fd00000(0000) knlGS:0000000000000000 >>>> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>>> CR2: 0000000020a5afd8 CR3: 000000020f8a9000 CR4: 00000000001406e0 >>>> Call Trace: >>>> check_object_size include/linux/thread_info.h:112 [inline] >>>> check_copy_size include/linux/thread_info.h:143 [inline] >>>> copy_to_user include/linux/uaccess.h:154 [inline] >>>> old_dev_ioctl.isra.1+0x21d/0x9a0 net/bridge/br_ioctl.c:178 >>> >>> Uhh, this doesn't make sense, much like the other report... >>> >>> indices = kcalloc(num, sizeof(int), GFP_KERNEL); >>> if (indices == NULL) >>> return -ENOMEM; >>> >>> get_port_ifindices(br, indices, num); >>> if (copy_to_user((void __user *)args[1], indices, >>> num*sizeof(int))) >>> >>> offset is 0. size overlaps. usercopy checks in -next must be broken. I >>> will double-check. >> >> >> Start of heap object ending at 0x59 looks bogus, right? > > No, that's a hashed address. %p doesn't report real addresses any more. Ah, for some reason I thought that 64-bit hashing just strips upper part (because what would be a reason to strip it from a hash? and showing lower bytes is useful and does not reveal too much). >>>> br_dev_ioctl+0x3f/0xa0 net/bridge/br_ioctl.c:392 >>>> dev_ifsioc+0x175/0x520 net/core/dev_ioctl.c:354 >>>> dev_ioctl+0x548/0x7a0 net/core/dev_ioctl.c:589 >>>> sock_ioctl+0x150/0x320 net/socket.c:998 >>>> vfs_ioctl fs/ioctl.c:46 [inline] >>>> do_vfs_ioctl+0xaf/0x840 fs/ioctl.c:686 >>>> SYSC_ioctl fs/ioctl.c:701 [inline] >>>> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692 >>>> entry_SYSCALL_64_fastpath+0x1f/0x96 >>>> RIP: 0033:0x452a39 >>>> RSP: 002b:00007f61a06bbc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010 >>>> RAX: ffffffffffffffda RBX: 00007f61a06bc700 RCX: 0000000000452a39 >>>> RDX: 0000000020a59fd8 RSI: 00000000000089f0 RDI: 0000000000000014 >>>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 >>>> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000 >>>> R13: 0000000000a6f7ff R14: 00007f61a06bc9c0 R15: 0000000000000000 >>>> Code: 7b e5 82 48 0f 44 da e8 8d 82 eb ff 48 8b 45 d0 4d 89 e9 4c 89 e1 4c >>>> 89 fa 48 89 de 48 c7 c7 a8 51 e6 82 49 89 c0 e8 76 b7 e3 ff <0f> 0b 48 c7 c0 >>>> 43 51 e6 82 eb a1 48 c7 c0 53 51 e6 82 eb 98 48 >>>> RIP: report_usercopy mm/usercopy.c:76 [inline] RSP: ffffc9000116fc50 >>>> RIP: __check_object_size+0x1e2/0x250 mm/usercopy.c:276 RSP: ffffc9000116fc50 >>>> ---[ end trace 5fadb883cda020dc ]--- >>>> Kernel panic - not syncing: Fatal exception >>>> Dumping ftrace buffer: >>>> (ftrace buffer empty) >>>> Kernel Offset: disabled >>>> Rebooting in 86400 seconds.. >>>> >>>> >>>> --- >>>> This bug is generated by a dumb bot. It may contain errors. >>>> See https://goo.gl/tpsmEJ for details. >>>> Direct all questions to syzkaller@xxxxxxxxxxxxxxxx. >>>> Please credit me with: Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx> >>>> >>>> syzbot will keep track of this bug report. >>>> Once a fix for this bug is merged into any tree, reply to this email with: >>>> #syz fix: exact-commit-title >>>> To mark this as a duplicate of another syzbot report, please reply with: >>>> #syz dup: exact-subject-of-another-report >>>> If it's a one-off invalid bug report, please reply with: >>>> #syz invalid >>>> Note: if the crash happens again, it will cause creation of a new bug >>>> report. >>>> Note: all commands must start from beginning of the line in the email body. >>> >>> >>> >>> -- >>> Kees Cook >>> Pixel Security >>> >>> -- >>> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. >>> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. >>> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/CAGXu5jLAvE9GaF%3DVdzR%3DwrUpquDSJkUXCidZMU-qb02%2BFDZW6g%40mail.gmail.com. >>> For more options, visit https://groups.google.com/d/optout. > > > > -- > Kees Cook > Pixel Security -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. 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