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Message-ID: <f7c64050-bbb6-be37-ec09-cb757bad116a@redhat.com>
Date: Wed, 6 Dec 2017 11:22:55 -0800
From: Laura Abbott <labbott@...hat.com>
To: Alexander Popov <alex.popov@...ux.com>,
kernel-hardening@...ts.openwall.com, Kees Cook <keescook@...omium.org>,
PaX Team <pageexec@...email.hu>, Brad Spengler <spender@...ecurity.net>,
Ingo Molnar <mingo@...nel.org>, Andy Lutomirski <luto@...nel.org>,
Tycho Andersen <tycho@...ho.ws>, Mark Rutland <mark.rutland@....com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>, Borislav Petkov <bp@...en8.de>,
Thomas Gleixner <tglx@...utronix.de>, "H . Peter Anvin" <hpa@...or.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>, x86@...nel.org
Subject: Re: [PATCH RFC v6 5/6] fs/proc: Show STACKLEAK metrics in the /proc
file system
On 12/05/2017 03:33 PM, Alexander Popov wrote:
> Introduce CONFIG_STACKLEAK_METRICS providing STACKLEAK information about
> tasks via the /proc file system. In particular, /proc/<pid>/lowest_stack
> shows the current lowest_stack value and its final value from the previous
> syscall. That information can be useful for estimating the STACKLEAK
> performance impact for different workloads.
>
> Signed-off-by: Alexander Popov <alex.popov@...ux.com>
> ---
> arch/Kconfig | 11 +++++++++++
> arch/x86/entry/entry_32.S | 4 ++++
> arch/x86/entry/entry_64.S | 4 ++++
> arch/x86/include/asm/processor.h | 3 +++
> arch/x86/kernel/asm-offsets.c | 3 +++
> arch/x86/kernel/process_32.c | 3 +++
> arch/x86/kernel/process_64.c | 3 +++
> fs/proc/base.c | 14 ++++++++++++++
> 8 files changed, 45 insertions(+)
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index ba8e67b..3d8405c 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -559,6 +559,17 @@ config STACKLEAK_TRACK_MIN_SIZE
> this setting, don't break the poison search in erase_kstack.
> If unsure, leave the default value 100.
>
> +config STACKLEAK_METRICS
> + bool "Show STACKLEAK metrics in the /proc file system"
> + depends on GCC_PLUGIN_STACKLEAK
> + depends on PROC_FS
> + help
> + If this is set, STACKLEAK metrics for every task are available in
> + the /proc file system. In particular, /proc/<pid>/lowest_stack
> + shows the current lowest_stack value and its final value from the
> + previous syscall. That information can be useful for estimating
> + the STACKLEAK performance impact for your workloads.
> +
> config HAVE_CC_STACKPROTECTOR
> bool
> help
> diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
> index 8e4f815..2b76020 100644
> --- a/arch/x86/entry/entry_32.S
> +++ b/arch/x86/entry/entry_32.S
> @@ -116,6 +116,10 @@ ENTRY(erase_kstack)
> mov %esp, %ecx
> sub %edi, %ecx
>
> +#ifdef CONFIG_STACKLEAK_METRICS
> + mov %edi, TASK_prev_lowest_stack(%ebp)
> +#endif
> +
> cmp $THREAD_SIZE_asm, %ecx
> jb 3f
> ud2
> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> index 94f659d..32ee040 100644
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -121,6 +121,10 @@ ENTRY(erase_kstack)
> mov %esp, %ecx
> sub %edi, %ecx
>
> +#ifdef CONFIG_STACKLEAK_METRICS
> + mov %rdi, TASK_prev_lowest_stack(%r11)
> +#endif
> +
> /* Check that the counter value is sane. */
> cmp $THREAD_SIZE_asm, %rcx
> jb 3f
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 520508d..c94fc2f 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -483,6 +483,9 @@ struct thread_struct {
>
> #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
> unsigned long lowest_stack;
> +# ifdef CONFIG_STACKLEAK_METRICS
> + unsigned long prev_lowest_stack;
> +# endif
> #endif
>
> unsigned int sig_on_uaccess_err:1;
> diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
> index 692c10e..84c5a29 100644
> --- a/arch/x86/kernel/asm-offsets.c
> +++ b/arch/x86/kernel/asm-offsets.c
> @@ -43,6 +43,9 @@ void common(void) {
> # ifdef CONFIG_X86_32
> OFFSET(TASK_thread_sp0, task_struct, thread.sp0);
> # endif
> +# ifdef CONFIG_STACKLEAK_METRICS
> + OFFSET(TASK_prev_lowest_stack, task_struct, thread.prev_lowest_stack);
> +# endif
> #endif
>
> BLANK();
> diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
> index 2bea3bf..5615b3d 100644
> --- a/arch/x86/kernel/process_32.c
> +++ b/arch/x86/kernel/process_32.c
> @@ -139,6 +139,9 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
> #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
> p->thread.lowest_stack = (unsigned long)task_stack_page(p) +
> 2 * sizeof(unsigned long);
> +# ifdef CONFIG_STACKLEAK_METRICS
> + p->thread.prev_lowest_stack = p->thread.lowest_stack;
> +# endif
> #endif
>
> if (unlikely(p->flags & PF_KTHREAD)) {
> diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
> index 1641463..d4a50ef 100644
> --- a/arch/x86/kernel/process_64.c
> +++ b/arch/x86/kernel/process_64.c
> @@ -285,6 +285,9 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp,
> #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
> p->thread.lowest_stack = (unsigned long)task_stack_page(p) +
> 2 * sizeof(unsigned long);
> +# ifdef CONFIG_STACKLEAK_METRICS
> + p->thread.prev_lowest_stack = p->thread.lowest_stack;
> +# endif
> #endif
>
> savesegment(gs, p->thread.gsindex);
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 28fa852..3569446 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -2884,6 +2884,17 @@ static int proc_pid_patch_state(struct seq_file *m, struct pid_namespace *ns,
> }
> #endif /* CONFIG_LIVEPATCH */
>
> +#ifdef CONFIG_STACKLEAK_METRICS
> +static int proc_lowest_stack(struct seq_file *m, struct pid_namespace *ns,
> + struct pid *pid, struct task_struct *task)
> +{
> + seq_printf(m, "prev_lowest_stack: %pK\nlowest_stack: %pK\n",
> + (void *)task->thread.prev_lowest_stack,
> + (void *)task->thread.lowest_stack);
> + return 0;
> +}
> +#endif /* CONFIG_STACKLEAK_METRICS */
> +
This just prints the hashed value with the new pointer leak work.
I don't think we want to print the fully exposed value via %px so
it's not clear how valuable this proc file is now.
Thanks,
Laura
> /*
> * Thread groups
> */
> @@ -2988,6 +2999,9 @@ static const struct pid_entry tgid_base_stuff[] = {
> #ifdef CONFIG_LIVEPATCH
> ONE("patch_state", S_IRUSR, proc_pid_patch_state),
> #endif
> +#ifdef CONFIG_STACKLEAK_METRICS
> + ONE("lowest_stack", S_IRUGO, proc_lowest_stack),
> +#endif
> };
>
> static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx)
>
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