* BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970
@ 2017-10-11 1:28 Jakub Kicinski
2017-10-11 1:44 ` Tyler Hicks
0 siblings, 1 reply; 6+ messages in thread
From: Jakub Kicinski @ 2017-10-11 1:28 UTC (permalink / raw)
To: Tyler Hicks, Kees Cook; +Cc: LKML
I'm hitting this on sysctl -a with net-next (4.14-rc4).
I saw that seccomp_actions_logged_handler was introduced
not-so-long-ago by Tyler, is there a fix for this?
[ 753.503760] BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970
[ 753.510892] Read of size 8 at addr ffffffffa96b97c8 by task sysctl/1787
[ 753.518416]
[ 753.520198] CPU: 1 PID: 1787 Comm: sysctl Not tainted 4.14.0-rc4-debug-00822-g07ec06ef312a #316
[ 753.538598] Call Trace:
[ 753.541449] dump_stack+0xb3/0x140
[ 753.545372] ? _atomic_dec_and_lock+0x2b0/0x2b0
[ 753.550564] ? show_regs_print_info+0x6d/0x6d
[ 753.555562] print_address_description+0x25f/0x440
[ 753.561044] ? strscpy+0x807/0x970
[ 753.564967] kasan_report+0x1b8/0x430
[ 753.569182] ? strscpy+0x807/0x970
[ 753.573107] strscpy+0x807/0x970
[ 753.576838] ? strncpy+0xf0/0xf0
[ 753.580576] ? sched_clock_cpu+0x18/0x290
[ 753.585185] seccomp_actions_logged_handler+0x384/0x8d0
[ 753.591157] ? seccomp_send_sigsys+0xa0/0xa0
[ 753.596046] ? lock_downgrade+0x740/0x740
[ 753.600648] ? get_lock_stats+0x18/0x160
[ 753.605159] ? sysctl_head_grab+0x1b/0xc0
[ 753.609766] ? lock_contended+0x1130/0x1130
[ 753.614566] ? lock_release+0x14e0/0x14e0
[ 753.619171] ? do_raw_spin_trylock+0x1c0/0x1c0
[ 753.624261] ? lock_downgrade+0x660/0x740
[ 753.628858] ? do_raw_spin_lock+0x1f0/0x1f0
[ 753.633657] proc_sys_call_handler+0x216/0x3c0
[ 753.638752] ? proc_sys_permission+0x250/0x250
[ 753.643847] ? do_mmap+0x622/0xf50
[ 753.647772] __vfs_read+0xea/0x9a0
[ 753.651696] ? vfs_copy_file_range+0xc60/0xc60
[ 753.656787] ? security_mmap_file+0x66/0x1d0
[ 753.661686] ? common_file_perm+0x1e0/0x6b0
[ 753.666485] ? vm_mmap_pgoff+0x1b6/0x250
[ 753.670993] ? fsnotify+0x1c80/0x1c80
[ 753.675209] ? apparmor_task_setrlimit+0x690/0x690
[ 753.680687] ? vma_is_stack_for_current+0xb0/0xb0
[ 753.686073] vfs_read+0x109/0x3e0
[ 753.689900] SyS_read+0xcc/0x1d0
[ 753.693628] ? kernel_write+0x1a0/0x1a0
[ 753.698034] ? trace_hardirqs_on_caller+0x3cb/0x680
[ 753.703610] ? trace_hardirqs_on_thunk+0x1a/0x1c
[ 753.708898] entry_SYSCALL_64_fastpath+0x1c/0xb1
[ 753.714180] RIP: 0033:0x7f62c82296b0
[ 753.718294] RSP: 002b:00007ffc2d6726c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[ 753.726919] RAX: ffffffffffffffda RBX: 0000000000000046 RCX: 00007f62c82296b0
[ 753.735028] RDX: 0000000000000400 RSI: 00007f62c8722000 RDI: 0000000000000006
[ 753.743138] RBP: 0000000000000000 R08: 00000000ffffffff R09: 0000000000000000
[ 753.751246] R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000000000
[ 753.759355] R13: 0000000001d63650 R14: 00007f62c87186a0 R15: 0000000000000028
[ 753.767478]
[ 753.769256] The buggy address belongs to the variable:
[ 753.775125] kprobes_seq_ops+0x1268/0x15c0
[ 753.779820]
[ 753.781595] Memory state around the buggy address:
[ 753.787075] ffffffffa96b9680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 753.795301] ffffffffa96b9700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 753.803526] >ffffffffa96b9780: 07 fa fa fa fa fa fa fa 00 05 fa fa fa fa fa fa
[ 753.811751] ^
[ 753.818105] ffffffffa96b9800: 02 fa fa fa fa fa fa fa 00 00 04 fa fa fa fa fa
[ 753.826330] ffffffffa96b9880: 00 00 00 01 fa fa fa fa 00 00 00 00 01 fa fa fa
[ 753.834554] ==================================================================
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970
2017-10-11 1:28 BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970 Jakub Kicinski
@ 2017-10-11 1:44 ` Tyler Hicks
2017-10-11 1:46 ` Jakub Kicinski
0 siblings, 1 reply; 6+ messages in thread
From: Tyler Hicks @ 2017-10-11 1:44 UTC (permalink / raw)
To: Jakub Kicinski, Kees Cook; +Cc: LKML
[-- Attachment #1.1: Type: text/plain, Size: 3788 bytes --]
On 10/10/2017 09:28 PM, Jakub Kicinski wrote:
> I'm hitting this on sysctl -a with net-next (4.14-rc4).
Hey Jakub - thanks for the bug report!
>
> I saw that seccomp_actions_logged_handler was introduced
> not-so-long-ago by Tyler, is there a fix for this?
No, this is the first I've heard of it. I'll have a look.
Tyler
>
> [ 753.503760] BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970
> [ 753.510892] Read of size 8 at addr ffffffffa96b97c8 by task sysctl/1787
> [ 753.518416]
> [ 753.520198] CPU: 1 PID: 1787 Comm: sysctl Not tainted 4.14.0-rc4-debug-00822-g07ec06ef312a #316
> [ 753.538598] Call Trace:
> [ 753.541449] dump_stack+0xb3/0x140
> [ 753.545372] ? _atomic_dec_and_lock+0x2b0/0x2b0
> [ 753.550564] ? show_regs_print_info+0x6d/0x6d
> [ 753.555562] print_address_description+0x25f/0x440
> [ 753.561044] ? strscpy+0x807/0x970
> [ 753.564967] kasan_report+0x1b8/0x430
> [ 753.569182] ? strscpy+0x807/0x970
> [ 753.573107] strscpy+0x807/0x970
> [ 753.576838] ? strncpy+0xf0/0xf0
> [ 753.580576] ? sched_clock_cpu+0x18/0x290
> [ 753.585185] seccomp_actions_logged_handler+0x384/0x8d0
> [ 753.591157] ? seccomp_send_sigsys+0xa0/0xa0
> [ 753.596046] ? lock_downgrade+0x740/0x740
> [ 753.600648] ? get_lock_stats+0x18/0x160
> [ 753.605159] ? sysctl_head_grab+0x1b/0xc0
> [ 753.609766] ? lock_contended+0x1130/0x1130
> [ 753.614566] ? lock_release+0x14e0/0x14e0
> [ 753.619171] ? do_raw_spin_trylock+0x1c0/0x1c0
> [ 753.624261] ? lock_downgrade+0x660/0x740
> [ 753.628858] ? do_raw_spin_lock+0x1f0/0x1f0
> [ 753.633657] proc_sys_call_handler+0x216/0x3c0
> [ 753.638752] ? proc_sys_permission+0x250/0x250
> [ 753.643847] ? do_mmap+0x622/0xf50
> [ 753.647772] __vfs_read+0xea/0x9a0
> [ 753.651696] ? vfs_copy_file_range+0xc60/0xc60
> [ 753.656787] ? security_mmap_file+0x66/0x1d0
> [ 753.661686] ? common_file_perm+0x1e0/0x6b0
> [ 753.666485] ? vm_mmap_pgoff+0x1b6/0x250
> [ 753.670993] ? fsnotify+0x1c80/0x1c80
> [ 753.675209] ? apparmor_task_setrlimit+0x690/0x690
> [ 753.680687] ? vma_is_stack_for_current+0xb0/0xb0
> [ 753.686073] vfs_read+0x109/0x3e0
> [ 753.689900] SyS_read+0xcc/0x1d0
> [ 753.693628] ? kernel_write+0x1a0/0x1a0
> [ 753.698034] ? trace_hardirqs_on_caller+0x3cb/0x680
> [ 753.703610] ? trace_hardirqs_on_thunk+0x1a/0x1c
> [ 753.708898] entry_SYSCALL_64_fastpath+0x1c/0xb1
> [ 753.714180] RIP: 0033:0x7f62c82296b0
> [ 753.718294] RSP: 002b:00007ffc2d6726c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> [ 753.726919] RAX: ffffffffffffffda RBX: 0000000000000046 RCX: 00007f62c82296b0
> [ 753.735028] RDX: 0000000000000400 RSI: 00007f62c8722000 RDI: 0000000000000006
> [ 753.743138] RBP: 0000000000000000 R08: 00000000ffffffff R09: 0000000000000000
> [ 753.751246] R10: 0000000000000022 R11: 0000000000000246 R12: 0000000000000000
> [ 753.759355] R13: 0000000001d63650 R14: 00007f62c87186a0 R15: 0000000000000028
> [ 753.767478]
> [ 753.769256] The buggy address belongs to the variable:
> [ 753.775125] kprobes_seq_ops+0x1268/0x15c0
> [ 753.779820]
> [ 753.781595] Memory state around the buggy address:
> [ 753.787075] ffffffffa96b9680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [ 753.795301] ffffffffa96b9700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [ 753.803526] >ffffffffa96b9780: 07 fa fa fa fa fa fa fa 00 05 fa fa fa fa fa fa
> [ 753.811751] ^
> [ 753.818105] ffffffffa96b9800: 02 fa fa fa fa fa fa fa 00 00 04 fa fa fa fa fa
> [ 753.826330] ffffffffa96b9880: 00 00 00 01 fa fa fa fa 00 00 00 00 01 fa fa fa
> [ 753.834554] ==================================================================
>
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 801 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970
2017-10-11 1:44 ` Tyler Hicks
@ 2017-10-11 1:46 ` Jakub Kicinski
2017-10-11 2:37 ` Simon Brewer
[not found] ` <CAEeGbKOtffFD9Fb3qRc-8DkkQsAhuVO3X3xuzFtxH2p1uT69RQ@mail.gmail.com>
0 siblings, 2 replies; 6+ messages in thread
From: Jakub Kicinski @ 2017-10-11 1:46 UTC (permalink / raw)
To: Tyler Hicks; +Cc: Kees Cook, LKML
On Tue, 10 Oct 2017 21:44:01 -0400, Tyler Hicks wrote:
> On 10/10/2017 09:28 PM, Jakub Kicinski wrote:
> > I'm hitting this on sysctl -a with net-next (4.14-rc4).
>
> Hey Jakub - thanks for the bug report!
>
> >
> > I saw that seccomp_actions_logged_handler was introduced
> > not-so-long-ago by Tyler, is there a fix for this?
>
> No, this is the first I've heard of it. I'll have a look.
Thanks! :)
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970
2017-10-11 1:46 ` Jakub Kicinski
@ 2017-10-11 2:37 ` Simon Brewer
[not found] ` <CAEeGbKOtffFD9Fb3qRc-8DkkQsAhuVO3X3xuzFtxH2p1uT69RQ@mail.gmail.com>
1 sibling, 0 replies; 6+ messages in thread
From: Simon Brewer @ 2017-10-11 2:37 UTC (permalink / raw)
To: Jakub Kicinski; +Cc: Tyler Hicks, Kees Cook, LKML
On 11 October 2017 at 12:46, Jakub Kicinski <kubakici@wp.pl> wrote:
> On Tue, 10 Oct 2017 21:44:01 -0400, Tyler Hicks wrote:
>> On 10/10/2017 09:28 PM, Jakub Kicinski wrote:
>> > I'm hitting this on sysctl -a with net-next (4.14-rc4).
>>
>> Hey Jakub - thanks for the bug report!
>>
>> >
>> > I saw that seccomp_actions_logged_handler was introduced
>> > not-so-long-ago by Tyler, is there a fix for this?
>>
>> No, this is the first I've heard of it. I'll have a look.
>
> Thanks! :)
Hint: start looking at this thread. https://lkml.org/lkml/2017/7/18/874
Summary: strscpy and KASAN are currently incompatible. strscpy does a
64 bit speculative fetch on a char pointer (for efficiency reasons).
KASAN spots this and flags an error.
^ permalink raw reply [flat|nested] 6+ messages in thread[parent not found: <CAEeGbKOtffFD9Fb3qRc-8DkkQsAhuVO3X3xuzFtxH2p1uT69RQ@mail.gmail.com>]
* Re: BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970
[not found] ` <CAEeGbKOtffFD9Fb3qRc-8DkkQsAhuVO3X3xuzFtxH2p1uT69RQ@mail.gmail.com>
@ 2017-10-11 4:37 ` Tyler Hicks
2017-10-11 7:21 ` Kees Cook
0 siblings, 1 reply; 6+ messages in thread
From: Tyler Hicks @ 2017-10-11 4:37 UTC (permalink / raw)
To: Jakub Kicinski, Kees Cook; +Cc: Simon Brewer, LKML
[-- Attachment #1.1: Type: text/plain, Size: 1408 bytes --]
On 10/10/2017 10:32 PM, Simon Brewer wrote:
> Hint start looking at this thread. https://lkml.org/lkml/2017/7/18/874
>
> Summary: strscpy and KASAN are currently incompatible. strscpy does a
> 64 bit speculative fetch on a char pointer (for efficiency reasons).
> KASAN spots this and flags an error.
Thanks, Simon. I had already reviewed the loop in
seccomp_names_from_actions_logged() and couldn't spot an issue so my
next step was to take a look at strscpy() itself. Your reply was well
timed. :)
@Kees, this is a false positive. I picked strscpy() because of its sane
return codes for easy error handling but its word-at-a-time complexity
is overkill for this sysctl. Are you alright with this KASAN false
positive or would you like me to change over to strlcpy()?
Tyler
>
> On 11 October 2017 at 12:46, Jakub Kicinski <kubakici@wp.pl
> <mailto:kubakici@wp.pl>> wrote:
>
> On Tue, 10 Oct 2017 21:44:01 -0400, Tyler Hicks wrote:
> > On 10/10/2017 09:28 PM, Jakub Kicinski wrote:
> > > I'm hitting this on sysctl -a with net-next (4.14-rc4).
> >
> > Hey Jakub - thanks for the bug report!
> >
> > >
> > > I saw that seccomp_actions_logged_handler was introduced
> > > not-so-long-ago by Tyler, is there a fix for this?
> >
> > No, this is the first I've heard of it. I'll have a look.
>
> Thanks! :)
>
>
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 801 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970
2017-10-11 4:37 ` Tyler Hicks
@ 2017-10-11 7:21 ` Kees Cook
0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2017-10-11 7:21 UTC (permalink / raw)
To: Tyler Hicks; +Cc: Jakub Kicinski, Simon Brewer, LKML
On Tue, Oct 10, 2017 at 9:37 PM, Tyler Hicks <tyhicks@canonical.com> wrote:
> On 10/10/2017 10:32 PM, Simon Brewer wrote:
>> Hint start looking at this thread. https://lkml.org/lkml/2017/7/18/874
>>
>> Summary: strscpy and KASAN are currently incompatible. strscpy does a
>> 64 bit speculative fetch on a char pointer (for efficiency reasons).
>> KASAN spots this and flags an error.
>
> Thanks, Simon. I had already reviewed the loop in
> seccomp_names_from_actions_logged() and couldn't spot an issue so my
> next step was to take a look at strscpy() itself. Your reply was well
> timed. :)
>
> @Kees, this is a false positive. I picked strscpy() because of its sane
> return codes for easy error handling but its word-at-a-time complexity
> is overkill for this sysctl. Are you alright with this KASAN false
> positive or would you like me to change over to strlcpy()?
I tend to prefer strscpy. I don't think we need a change here. Thanks!
-Kees
--
Kees Cook
Pixel Security
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-10-11 7:21 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-10-11 1:28 BUG: KASAN: global-out-of-bounds in strscpy+0x807/0x970 Jakub Kicinski
2017-10-11 1:44 ` Tyler Hicks
2017-10-11 1:46 ` Jakub Kicinski
2017-10-11 2:37 ` Simon Brewer
[not found] ` <CAEeGbKOtffFD9Fb3qRc-8DkkQsAhuVO3X3xuzFtxH2p1uT69RQ@mail.gmail.com>
2017-10-11 4:37 ` Tyler Hicks
2017-10-11 7:21 ` Kees Cook
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.