Messages in this thread | | | Date | Wed, 18 Mar 2020 11:06:50 +0100 | From | Greg KH <> | Subject | Re: KASAN: use-after-free Read in vt_do_kdgkb_ioctl |
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On Mon, Feb 24, 2020 at 09:00:28PM +0800, Hillf Danton wrote: > > On Mon, 24 Feb 2020 01:18:14 -0800 > > syzbot found the following crash on: > > > > HEAD commit: 54dedb5b Merge tag 'for-linus-5.6-rc3-tag' of git://git.ke.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=100403d9e00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=3b8906eb6a7d6028 > > dashboard link: https://syzkaller.appspot.com/bug?extid=a58bfd517766aef83043 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > > Unfortunately, I don't have any reproducer for this crash yet. > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+a58bfd517766aef83043@syzkaller.appspotmail.com > > > > ================================================================== > > BUG: KASAN: use-after-free in vt_do_kdgkb_ioctl+0xb24/0xb50 drivers/tty/vt/keyboard.c:2025 > > Read of size 1 at addr ffff8880a4a8c801 by task syz-executor.4/27890 > > > > CPU: 1 PID: 27890 Comm: syz-executor.4 Not tainted 5.6.0-rc2-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0x197/0x210 lib/dump_stack.c:118 > > print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 > > __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506 > > kasan_report+0x12/0x20 mm/kasan/common.c:641 > > __asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:132 > > vt_do_kdgkb_ioctl+0xb24/0xb50 drivers/tty/vt/keyboard.c:2025 > > vt_ioctl+0x47e/0x26c0 drivers/tty/vt/vt_ioctl.c:549 > > tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2660 > > vfs_ioctl fs/ioctl.c:47 [inline] > > ksys_ioctl+0x123/0x180 fs/ioctl.c:763 > > __do_sys_ioctl fs/ioctl.c:772 [inline] > > __se_sys_ioctl fs/ioctl.c:770 [inline] > > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770 > > do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > RIP: 0033:0x45c429 > > Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > > RSP: 002b:00007f0f2868cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > > RAX: ffffffffffffffda RBX: 00007f0f2868d6d4 RCX: 000000000045c429 > > RDX: 0000000020000200 RSI: 0000000000004b48 RDI: 0000000000000003 > > RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff > > R13: 000000000000041a R14: 00000000004c676d R15: 000000000076bf2c > > > > Allocated by task 1548: > > save_stack+0x23/0x90 mm/kasan/common.c:72 > > set_track mm/kasan/common.c:80 [inline] > > __kasan_kmalloc mm/kasan/common.c:515 [inline] > > __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:488 > > kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529 > > __do_kmalloc mm/slab.c:3656 [inline] > > __kmalloc+0x163/0x770 mm/slab.c:3665 > > kmalloc include/linux/slab.h:560 [inline] > > vt_do_kdgkb_ioctl+0x3d1/0xb50 drivers/tty/vt/keyboard.c:2078 > > vt_ioctl+0x47e/0x26c0 drivers/tty/vt/vt_ioctl.c:549 > > tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2660 > > vfs_ioctl fs/ioctl.c:47 [inline] > > ksys_ioctl+0x123/0x180 fs/ioctl.c:763 > > __do_sys_ioctl fs/ioctl.c:772 [inline] > > __se_sys_ioctl fs/ioctl.c:770 [inline] > > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770 > > do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > Freed by task 27892: > > save_stack+0x23/0x90 mm/kasan/common.c:72 > > set_track mm/kasan/common.c:80 [inline] > > kasan_set_free_info mm/kasan/common.c:337 [inline] > > __kasan_slab_free+0x102/0x150 mm/kasan/common.c:476 > > kasan_slab_free+0xe/0x10 mm/kasan/common.c:485 > > __cache_free mm/slab.c:3426 [inline] > > kfree+0x10a/0x2c0 mm/slab.c:3757 > > vt_do_kdgkb_ioctl+0x5b4/0xb50 drivers/tty/vt/keyboard.c:2104 > > vt_ioctl+0x47e/0x26c0 drivers/tty/vt/vt_ioctl.c:549 > > tty_ioctl+0xa37/0x14f0 drivers/tty/tty_io.c:2660 > > vfs_ioctl fs/ioctl.c:47 [inline] > > ksys_ioctl+0x123/0x180 fs/ioctl.c:763 > > __do_sys_ioctl fs/ioctl.c:772 [inline] > > __se_sys_ioctl fs/ioctl.c:770 [inline] > > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:770 > > do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > > The buggy address belongs to the object at ffff8880a4a8c800 > > which belongs to the cache kmalloc-1k of size 1024 > > The buggy address is located 1 bytes inside of > > 1024-byte region [ffff8880a4a8c800, ffff8880a4a8cc00) > > The buggy address belongs to the page: > > page:ffffea000292a300 refcount:1 mapcount:0 mapping:ffff8880aa400c40 index:0x0 > > flags: 0xfffe0000000200(slab) > > raw: 00fffe0000000200 ffffea00026aa6c8 ffffea000210b1c8 ffff8880aa400c40 > > raw: 0000000000000000 ffff8880a4a8c000 0000000100000002 0000000000000000 > > page dumped because: kasan: bad access detected > > > > Memory state around the buggy address: > > ffff8880a4a8c700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > > ffff8880a4a8c780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > > >ffff8880a4a8c800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ^ > > ffff8880a4a8c880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ffff8880a4a8c900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > > ================================================================== > > Allocate a tmp buf for duplicating the string under lock and use it > outside lock. > > --- a/drivers/tty/vt/keyboard.c > +++ b/drivers/tty/vt/keyboard.c > @@ -1995,7 +1995,7 @@ int vt_do_kdgkb_ioctl(int cmd, struct kb > int delta; > char *first_free, *fj, *fnw; > int i, j, k; > - int ret; > + int ret = 0; > unsigned long flags; > > if (!capable(CAP_SYS_TTY_CONFIG)) > @@ -2021,18 +2021,45 @@ int vt_do_kdgkb_ioctl(int cmd, struct kb > a struct member */ > up = user_kdgkb->kb_string; > p = func_table[i]; > - if(p) > + if (p) { > + char *tmp_buf = kzalloc(sz + 1, GFP_KERNEL); > + > + if (!tmp_buf) { > + ret = -ENOMEM; > + goto reterr; > + } > + > + spin_lock_irqsave(&func_buf_lock, flags); > + p = func_table[i]; > + if (p) { > + __kernel_size_t len = strlen(p); > + if (sz < len) { > + ret = -EOVERFLOW; > + p = NULL; > + } else { > + memcpy(tmp_buf, p, len); > + p = tmp_buf; > + } > + } > + spin_unlock_irqrestore(&func_buf_lock, flags); > + if (!p) > + goto free_buf; > + > for ( ; *p && sz; p++, sz--) > if (put_user(*p, up++)) { > ret = -EFAULT; > - goto reterr; > + goto free_buf; > } > - if (put_user('\0', up)) { > - ret = -EFAULT; > - goto reterr; > + > +free_buf: > + kfree(tmp_buf); > + if (ret) > + goto reterr; > } > - kfree(kbs); > - return ((p && *p) ? -EOVERFLOW : 0); > + > + if (put_user('\0', up)) > + ret = -EFAULT; > + goto reterr; > case KDSKBSENT: > if (!perm) { > ret = -EPERM; >
What ever happened to this? Did it fix the issue? If so, can you resend this as a "real" patch I can apply?
thanks,
greg k-h
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