Re: general protection fault in spk_ttyio_ldisc_close
Greg KH, le mar. 08 janv. 2019 15:25:07 +0100, a ecrit: > On Tue, Jan 08, 2019 at 09:15:02AM -0500, Kyungtae Kim wrote: > > On Tue, Jan 8, 2019 at 8:50 AM Greg KH wrote: > > > > > > On Tue, Jan 08, 2019 at 08:37:37AM -0500, Kyungtae Kim wrote: > > > > We report a bug in linux-4.20: "general protection fault in > > > > spk_ttyio_ldisc_close" > > > > > > > > kernel config: https://kt0755.github.io/etc/config_v4.20_stable > > > > repro: https://kt0755.github.io/etc/repro.a670e.c > > > > > > > > This occurs when the function kfree is about to execute > > > > (driver/staging/speakup/spk_ttyio.c:68). > > > > Particularly, kfree takes the argument like speakup_tty->disc_data. > > > > But speakup_tty is invalid, so the pointer dereference causes GPF. > > > > At a glance, it seems that speakup_tty was deallocated somewhere ahead > > > > of kfree. > > > > > > How did you trigger this? Did you shut down and close the device > > > already somehow? Do you have a real tty device that is driven by the > > > device? > > > > > > thanks, > > > > > > greg k-h > > > > For this crash, we did without real speakup tty device. > > How did you bind a non-real speakup tty device to the driver? One can tell any device name to the driver and it will attempt to communicate with it. Samuel
Re: general protection fault in spk_ttyio_ldisc_close
On Tue, Jan 08, 2019 at 09:15:02AM -0500, Kyungtae Kim wrote: > On Tue, Jan 8, 2019 at 8:50 AM Greg KH wrote: > > > > On Tue, Jan 08, 2019 at 08:37:37AM -0500, Kyungtae Kim wrote: > > > We report a bug in linux-4.20: "general protection fault in > > > spk_ttyio_ldisc_close" > > > > > > kernel config: https://kt0755.github.io/etc/config_v4.20_stable > > > repro: https://kt0755.github.io/etc/repro.a670e.c > > > > > > This occurs when the function kfree is about to execute > > > (driver/staging/speakup/spk_ttyio.c:68). > > > Particularly, kfree takes the argument like speakup_tty->disc_data. > > > But speakup_tty is invalid, so the pointer dereference causes GPF. > > > At a glance, it seems that speakup_tty was deallocated somewhere ahead of > > > kfree. > > > > How did you trigger this? Did you shut down and close the device > > already somehow? Do you have a real tty device that is driven by the > > device? > > > > thanks, > > > > greg k-h > > For this crash, we did without real speakup tty device. How did you bind a non-real speakup tty device to the driver? > I'm currently trying to figure out how this actually happens. That would be great to figure out :) thanks, greg k-h
Re: general protection fault in spk_ttyio_ldisc_close
On Tue, Jan 8, 2019 at 8:50 AM Greg KH wrote: > > On Tue, Jan 08, 2019 at 08:37:37AM -0500, Kyungtae Kim wrote: > > We report a bug in linux-4.20: "general protection fault in > > spk_ttyio_ldisc_close" > > > > kernel config: https://kt0755.github.io/etc/config_v4.20_stable > > repro: https://kt0755.github.io/etc/repro.a670e.c > > > > This occurs when the function kfree is about to execute > > (driver/staging/speakup/spk_ttyio.c:68). > > Particularly, kfree takes the argument like speakup_tty->disc_data. > > But speakup_tty is invalid, so the pointer dereference causes GPF. > > At a glance, it seems that speakup_tty was deallocated somewhere ahead of > > kfree. > > How did you trigger this? Did you shut down and close the device > already somehow? Do you have a real tty device that is driven by the > device? > > thanks, > > greg k-h For this crash, we did without real speakup tty device. I'm currently trying to figure out how this actually happens. Thanks, Kyungtae Kim
Re: general protection fault in spk_ttyio_ldisc_close
On Tue, Jan 08, 2019 at 08:37:37AM -0500, Kyungtae Kim wrote: > We report a bug in linux-4.20: "general protection fault in > spk_ttyio_ldisc_close" > > kernel config: https://kt0755.github.io/etc/config_v4.20_stable > repro: https://kt0755.github.io/etc/repro.a670e.c > > This occurs when the function kfree is about to execute > (driver/staging/speakup/spk_ttyio.c:68). > Particularly, kfree takes the argument like speakup_tty->disc_data. > But speakup_tty is invalid, so the pointer dereference causes GPF. > At a glance, it seems that speakup_tty was deallocated somewhere ahead of > kfree. How did you trigger this? Did you shut down and close the device already somehow? Do you have a real tty device that is driven by the device? thanks, greg k-h
general protection fault in spk_ttyio_ldisc_close
We report a bug in linux-4.20: "general protection fault in spk_ttyio_ldisc_close" kernel config: https://kt0755.github.io/etc/config_v4.20_stable repro: https://kt0755.github.io/etc/repro.a670e.c This occurs when the function kfree is about to execute (driver/staging/speakup/spk_ttyio.c:68). Particularly, kfree takes the argument like speakup_tty->disc_data. But speakup_tty is invalid, so the pointer dereference causes GPF. At a glance, it seems that speakup_tty was deallocated somewhere ahead of kfree. = general protection fault: [#1] PREEMPT SMP KASAN PTI CPU: 0 PID: 13246 Comm: syz-executor7 Not tainted 4.20.0-rc2 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 RIP: 0010:spk_ttyio_ldisc_close+0x3f/0x80 drivers/staging/speakup/spk_ttyio.c:68 Code: 35 95 8c e8 43 03 60 01 48 8b 1d dc 2e 3f 07 48 ba 00 00 00 00 00 fc ff df 48 8d bb 70 05 00 00 48 89 f8 48 c1 e8 03 48 01 d0 <80> 38 00 75 26 48 8b bb 70 05 00 00 e8 a0 68 4f fa 48 c7 c7 c0 35 RSP: 0018:88810e6f7960 EFLAGS: 00010282 RAX: dcae RBX: RCX: 111021cdef00 RDX: dc00 RSI: 0008 RDI: 0570 RBP: 88810e6f7968 R08: fbfff192a6b9 R09: fbfff192a6b9 R10: 88810e6f7950 R11: fbfff192a6b8 R12: 8881063ee6b0 R13: 87471020 R14: 8881063eeea8 R15: 888116ec7b80 FS: 7f607f746700() GS:88811a00() knlGS: CS: 0010 DS: ES: CR0: 80050033 CR2: 006fb2e0 CR3: 00010f186000 CR4: 06f0 DR0: DR1: DR2: DR3: DR6: fffe0ff0 DR7: 0400 Call Trace: tty_ldisc_close drivers/tty/tty_ldisc.c:477 [inline] tty_ldisc_kill+0xef/0x1a0 drivers/tty/tty_ldisc.c:623 tty_ldisc_release+0x111/0x230 drivers/tty/tty_ldisc.c:790 tty_release_struct+0x1f/0x60 drivers/tty/tty_io.c:1595 tty_release+0xb80/0x11c0 drivers/tty/tty_io.c:1768 __fput+0x2b8/0x7a0 fs/file_table.c:278 fput+0x1a/0x20 fs/file_table.c:309 task_work_run+0x15b/0x1e0 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x8d6/0x30d0 kernel/exit.c:867 do_group_exit+0x13d/0x370 kernel/exit.c:970 get_signal+0x6bb/0x1890 kernel/signal.c:2517 do_signal+0x8c/0x1a10 arch/x86/kernel/signal.c:816 exit_to_usermode_loop+0x186/0x1d0 arch/x86/entry/common.c:162 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x445/0x4f0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4497b9 Code: e8 8c 9f 02 00 48 83 c4 18 c3 0f 1f 80 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 0f 83 9b 6b fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:7f607f745ce8 EFLAGS: 0246 ORIG_RAX: 00ca RAX: fe00 RBX: 0071bf80 RCX: 004497b9 RDX: RSI: RDI: 0071bf80 RBP: 0071bf80 R08: R09: 0071bf58 R10: R11: 0246 R12: R13: R14: 7f607f7469c0 R15: 7f607f746700 Modules linked in: Dumping ftrace buffer: (ftrace buffer empty) = Thanks, Kyungtae Kim
