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* v5.12+ regression on page_poison=1 i_on_free=0 i_on_alloc=0 warnings
@ 2021-07-11 23:57 Sergei Trofimovich
  2021-07-12 21:58 ` [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction Sergei Trofimovich
  0 siblings, 1 reply; 7+ messages in thread
From: Sergei Trofimovich @ 2021-07-11 23:57 UTC (permalink / raw)
  To: linux-mm, Kees Cook
  Cc: Thomas Gleixner, Alexander Potapenko, Vlastimil Babka,
	Andrey Konovalov, bowsingbetee

In
  https://bugs.gentoo.org/801481
  https://bugzilla.kernel.org/show_bug.cgi?id=213697
bowsingbetee noticed that the following setup causes kernel to complain
about poisoning on memset(0) pages:

- kernel command: page_poison=1 init_on_free=0 init_on_alloc=0
- kernel config:
  * CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
  * CONFIG_INIT_ON_FREE_DEFAULT_ON=y
  * CONFIG_PAGE_POISONING=y

v5.12 works ok, boots as:
  [    0.009691][    T0] mem auto-init: stack:off, heap alloc:off, heap free:off

v5.13 warns, boots as:
  [    0.009746][    T0] mem auto-init: stack:off, heap alloc:on, heap free:on

Current 5.14-rc1 is also affected:

[    0.009233][    T0] mem auto-init: stack:off, heap alloc:on, heap free:on
[    0.009234][    T0] mem auto-init: clearing system memory may take some time...
[    0.396784][    T0] pagealloc: memory corruption
[    0.396788][    T0] ffff888100000000: 00 00 00 00 00 00 00 00 00 00 00 00 00
                                         00 00 00  ................

I attempted to bisect it and found the follwing relevant commits:

Before the following commit no warnings were present:

  commit 51cba1ebc60df9c4ce034a9f5441169c0d0956c0
  Author: Kees Cook <keescook@chromium.org>
  Date:   Thu Apr 1 16:23:43 2021 -0700
    init_on_alloc: Optimize static branches

Next after this commit kernel does not boot. Makes it harder to
bisect the poisoning warning

After the commit below kernel boots and already complains about
poisoning of zero pages:

  commit 1bb5eab30d68c1a3d9dbc822e1895e6c06dbe748
  Author: Andrey Konovalov <andreyknvl@google.com>
  Date:   Thu Apr 29 23:00:02 2021 -0700
    kasan, mm: integrate page_alloc init with HW_TAGS

It looks like a case of page_poison=1 not having enough
of a priority over init_on_free=0 init_on_alloc=0 at early boot.

-- 

  Sergei


^ permalink raw reply	[flat|nested] 7+ messages in thread
* [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction
  2021-07-11 23:57 v5.12+ regression on page_poison=1 i_on_free=0 i_on_alloc=0 warnings Sergei Trofimovich
@ 2021-07-12 21:58 ` Sergei Trofimovich
  2021-07-14  2:00   ` Andrew Morton
  2021-07-14  3:10   ` Kees Cook
  0 siblings, 2 replies; 7+ messages in thread
From: Sergei Trofimovich @ 2021-07-12 21:58 UTC (permalink / raw)
  To: linux-mm
  Cc: linux-kernel, Sergei Trofimovich, Andrew Morton, Kees Cook,
	Alexander Potapenko, Thomas Gleixner, Vlastimil Babka,
	bowsingbetee

To reproduce the failure we need the following system:
  - kernel command: page_poison=1 init_on_free=0 init_on_alloc=0
  - kernel config:
    * CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
    * CONFIG_INIT_ON_FREE_DEFAULT_ON=y
    * CONFIG_PAGE_POISONING=y

    0000000085629bdd: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    0000000022861832: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00000000c597f5b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    CPU: 11 PID: 15195 Comm: bash Kdump: loaded Tainted: G     U     O      5.13.1-gentoo-x86_64 #1
    Hardware name: System manufacturer System Product Name/PRIME Z370-A, BIOS 2801 01/13/2021
    Call Trace:
     dump_stack+0x64/0x7c
     __kernel_unpoison_pages.cold+0x48/0x84
     post_alloc_hook+0x60/0xa0
     get_page_from_freelist+0xdb8/0x1000
     __alloc_pages+0x163/0x2b0
     __get_free_pages+0xc/0x30
     pgd_alloc+0x2e/0x1a0
     ? dup_mm+0x37/0x4f0
     mm_init+0x185/0x270
     dup_mm+0x6b/0x4f0
     ? __lock_task_sighand+0x35/0x70
     copy_process+0x190d/0x1b10
     kernel_clone+0xba/0x3b0
     __do_sys_clone+0x8f/0xb0
     do_syscall_64+0x68/0x80
     ? do_syscall_64+0x11/0x80
     entry_SYSCALL_64_after_hwframe+0x44/0xae

Before the 51cba1eb ("init_on_alloc: Optimize static branches")
init_on_alloc never enabled static branch by default. It could
only be enabed explicitly by init_mem_debugging_and_hardening().

But after the 51cba1eb static branch could already be enabled
by default. There was no code to ever disable it. That caused
page_poison=1 / init_on_free=1 conflict.

This change extends init_mem_debugging_and_hardening() to also
disable static branch disabling.

CC: Andrew Morton <akpm@linux-foundation.org>
CC: Kees Cook <keescook@chromium.org>
CC: Alexander Potapenko <glider@google.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Vlastimil Babka <vbabka@suse.cz>
CC: linux-mm@kvack.org
Reported-by: bowsingbetee@pm.me
Reported-by: Mikhail Morfikov
Fixes: 51cba1eb ("init_on_alloc: Optimize static branches")
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
---
 mm/page_alloc.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3b97e17806be..46cb4a9c2b50 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -840,18 +840,22 @@ void init_mem_debugging_and_hardening(void)
 	}
 #endif
 
-	if (_init_on_alloc_enabled_early) {
-		if (page_poisoning_requested)
+	if (_init_on_alloc_enabled_early ||
+	    IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON)) {
+		if (page_poisoning_requested) {
 			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
 				"will take precedence over init_on_alloc\n");
-		else
+			static_branch_disable(&init_on_alloc);
+		} else
 			static_branch_enable(&init_on_alloc);
 	}
-	if (_init_on_free_enabled_early) {
-		if (page_poisoning_requested)
+	if (_init_on_free_enabled_early ||
+	    IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON)) {
+		if (page_poisoning_requested) {
 			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
 				"will take precedence over init_on_free\n");
-		else
+			static_branch_disable(&init_on_free);
+		} else
 			static_branch_enable(&init_on_free);
 	}
 
-- 
2.32.0



^ permalink raw reply related	[flat|nested] 7+ messages in thread
* Re: [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction
  2021-07-12 21:58 ` [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction Sergei Trofimovich
@ 2021-07-14  2:00   ` Andrew Morton
  2021-07-17 18:18     ` Sergei Trofimovich
  2021-07-14  3:10   ` Kees Cook
  1 sibling, 1 reply; 7+ messages in thread
From: Andrew Morton @ 2021-07-14  2:00 UTC (permalink / raw)
  To: Sergei Trofimovich
  Cc: linux-mm, linux-kernel, Kees Cook, Alexander Potapenko,
	Thomas Gleixner, Vlastimil Babka, bowsingbetee

On Mon, 12 Jul 2021 22:58:16 +0100 Sergei Trofimovich <slyfox@gentoo.org> wrote:

> To reproduce the failure we need the following system:
>   - kernel command: page_poison=1 init_on_free=0 init_on_alloc=0
>   - kernel config:
>     * CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
>     * CONFIG_INIT_ON_FREE_DEFAULT_ON=y
>     * CONFIG_PAGE_POISONING=y
> 
>     0000000085629bdd: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     0000000022861832: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00000000c597f5b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     CPU: 11 PID: 15195 Comm: bash Kdump: loaded Tainted: G     U     O      5.13.1-gentoo-x86_64 #1
>     Hardware name: System manufacturer System Product Name/PRIME Z370-A, BIOS 2801 01/13/2021
>     Call Trace:
>      dump_stack+0x64/0x7c
>      __kernel_unpoison_pages.cold+0x48/0x84
>      post_alloc_hook+0x60/0xa0
>      get_page_from_freelist+0xdb8/0x1000
>      __alloc_pages+0x163/0x2b0
>      __get_free_pages+0xc/0x30
>      pgd_alloc+0x2e/0x1a0
>      ? dup_mm+0x37/0x4f0
>      mm_init+0x185/0x270
>      dup_mm+0x6b/0x4f0
>      ? __lock_task_sighand+0x35/0x70
>      copy_process+0x190d/0x1b10
>      kernel_clone+0xba/0x3b0
>      __do_sys_clone+0x8f/0xb0
>      do_syscall_64+0x68/0x80
>      ? do_syscall_64+0x11/0x80
>      entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Before the 51cba1eb ("init_on_alloc: Optimize static branches")
> init_on_alloc never enabled static branch by default. It could
> only be enabed explicitly by init_mem_debugging_and_hardening().
> 
> But after the 51cba1eb static branch could already be enabled
> by default. There was no code to ever disable it. That caused
> page_poison=1 / init_on_free=1 conflict.
> 
> This change extends init_mem_debugging_and_hardening() to also
> disable static branch disabling.
> 
> ...
>
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -840,18 +840,22 @@ void init_mem_debugging_and_hardening(void)
>  	}
>  #endif
>  
> -	if (_init_on_alloc_enabled_early) {
> -		if (page_poisoning_requested)
> +	if (_init_on_alloc_enabled_early ||
> +	    IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON)) {
> +		if (page_poisoning_requested) {
>  			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
>  				"will take precedence over init_on_alloc\n");
> -		else
> +			static_branch_disable(&init_on_alloc);
> +		} else
>  			static_branch_enable(&init_on_alloc);
>  	}
> -	if (_init_on_free_enabled_early) {
> -		if (page_poisoning_requested)
> +	if (_init_on_free_enabled_early ||
> +	    IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON)) {
> +		if (page_poisoning_requested) {
>  			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
>  				"will take precedence over init_on_free\n");
> -		else
> +			static_branch_disable(&init_on_free);
> +		} else
>  			static_branch_enable(&init_on_free);
>  	}
>  

I'm thinking this is sufficiently serious and sufficiently reported to
warrant a cc:stable backport.  Agree?



^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction
  2021-07-12 21:58 ` [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction Sergei Trofimovich
  2021-07-14  2:00   ` Andrew Morton
@ 2021-07-14  3:10   ` Kees Cook
  2021-07-14 11:11     ` bowsingbetee
  1 sibling, 1 reply; 7+ messages in thread
From: Kees Cook @ 2021-07-14  3:10 UTC (permalink / raw)
  To: Sergei Trofimovich
  Cc: linux-mm, linux-kernel, Andrew Morton, Alexander Potapenko,
	Thomas Gleixner, Vlastimil Babka, bowsingbetee

On Mon, Jul 12, 2021 at 10:58:16PM +0100, Sergei Trofimovich wrote:
> To reproduce the failure we need the following system:
>   - kernel command: page_poison=1 init_on_free=0 init_on_alloc=0
>   - kernel config:
>     * CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
>     * CONFIG_INIT_ON_FREE_DEFAULT_ON=y
>     * CONFIG_PAGE_POISONING=y
> 
>     0000000085629bdd: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     0000000022861832: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00000000c597f5b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     CPU: 11 PID: 15195 Comm: bash Kdump: loaded Tainted: G     U     O      5.13.1-gentoo-x86_64 #1
>     Hardware name: System manufacturer System Product Name/PRIME Z370-A, BIOS 2801 01/13/2021
>     Call Trace:
>      dump_stack+0x64/0x7c
>      __kernel_unpoison_pages.cold+0x48/0x84
>      post_alloc_hook+0x60/0xa0
>      get_page_from_freelist+0xdb8/0x1000
>      __alloc_pages+0x163/0x2b0
>      __get_free_pages+0xc/0x30
>      pgd_alloc+0x2e/0x1a0
>      ? dup_mm+0x37/0x4f0
>      mm_init+0x185/0x270
>      dup_mm+0x6b/0x4f0
>      ? __lock_task_sighand+0x35/0x70
>      copy_process+0x190d/0x1b10
>      kernel_clone+0xba/0x3b0
>      __do_sys_clone+0x8f/0xb0
>      do_syscall_64+0x68/0x80
>      ? do_syscall_64+0x11/0x80
>      entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> Before the 51cba1eb ("init_on_alloc: Optimize static branches")
> init_on_alloc never enabled static branch by default. It could
> only be enabed explicitly by init_mem_debugging_and_hardening().

But init_mem_debugging_and_hardening() is always called (by mm_init()).

> But after the 51cba1eb static branch could already be enabled
> by default. There was no code to ever disable it. That caused
> page_poison=1 / init_on_free=1 conflict.
> 
> This change extends init_mem_debugging_and_hardening() to also
> disable static branch disabling.
> 
> CC: Andrew Morton <akpm@linux-foundation.org>
> CC: Kees Cook <keescook@chromium.org>
> CC: Alexander Potapenko <glider@google.com>
> CC: Thomas Gleixner <tglx@linutronix.de>
> CC: Vlastimil Babka <vbabka@suse.cz>
> CC: linux-mm@kvack.org
> Reported-by: bowsingbetee@pm.me
> Reported-by: Mikhail Morfikov
> Fixes: 51cba1eb ("init_on_alloc: Optimize static branches")
> Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
> ---
>  mm/page_alloc.c | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3b97e17806be..46cb4a9c2b50 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -840,18 +840,22 @@ void init_mem_debugging_and_hardening(void)
>  	}
>  #endif
>  
> -	if (_init_on_alloc_enabled_early) {
> -		if (page_poisoning_requested)
> +	if (_init_on_alloc_enabled_early ||
> +	    IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON)) {

This doesn't look right. _init_on_alloc_enabled_early already has the
same value:

static bool _init_on_alloc_enabled_early __read_mostly
                                = IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON);

So checking this is just a side-effect of how static_branch_maybe()
happens to be behaving.

> +		if (page_poisoning_requested) {
>  			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
>  				"will take precedence over init_on_alloc\n");
> -		else
> +			static_branch_disable(&init_on_alloc);
> +		} else
>  			static_branch_enable(&init_on_alloc);
>  	}
> -	if (_init_on_free_enabled_early) {
> -		if (page_poisoning_requested)
> +	if (_init_on_free_enabled_early ||
> +	    IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON)) {
> +		if (page_poisoning_requested) {
>  			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
>  				"will take precedence over init_on_free\n");
> -		else
> +			static_branch_disable(&init_on_free);
> +		} else
>  			static_branch_enable(&init_on_free);
>  	}

I think it would be better to clean this up without additional
confusion involving the CONFIGs:

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3b97e17806be..1f19365bc158 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -840,21 +840,24 @@ void init_mem_debugging_and_hardening(void)
 	}
 #endif
 
-	if (_init_on_alloc_enabled_early) {
-		if (page_poisoning_requested)
-			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
-				"will take precedence over init_on_alloc\n");
-		else
-			static_branch_enable(&init_on_alloc);
-	}
-	if (_init_on_free_enabled_early) {
-		if (page_poisoning_requested)
-			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
-				"will take precedence over init_on_free\n");
-		else
-			static_branch_enable(&init_on_free);
+	if ((_init_on_alloc_enabled_early || _init_on_free_enabled_early) &&
+	    page_poisoning_requested) {
+		pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
+			"will take precedence over init_on_alloc and init_on_free\n");
+		_init_on_alloc_enabled_early = false;
+		_init_on_free_enabled_early = false;
 	}
 
+	if (_init_on_alloc_enabled_early)
+		static_branch_enable(&init_on_alloc);
+	else
+		static_branch_disable(&init_on_alloc);
+
+	if (_init_on_free_enabled_early)
+		static_branch_enable(&init_on_free);
+	else
+		static_branch_disable(&init_on_free);
+
 #ifdef CONFIG_DEBUG_PAGEALLOC
 	if (!debug_pagealloc_enabled())
 		return;

-- 
Kees Cook


^ permalink raw reply related	[flat|nested] 7+ messages in thread
* Re: [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction
  2021-07-14  3:10   ` Kees Cook
@ 2021-07-14 11:11     ` bowsingbetee
  2021-07-14 21:14       ` Kees Cook
  0 siblings, 1 reply; 7+ messages in thread
From: bowsingbetee @ 2021-07-14 11:11 UTC (permalink / raw)
  To: Kees Cook
  Cc: Sergei Trofimovich, linux-mm, linux-kernel, Andrew Morton,
	Alexander Potapenko, Thomas Gleixner, Vlastimil Babka


[-- Attachment #1.1: Type: text/plain, Size: 8604 bytes --]


‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐

On Wednesday, July 14th, 2021 at 5:10 AM, Kees Cook <keescook@chromium.org> wrote:

> On Mon, Jul 12, 2021 at 10:58:16PM +0100, Sergei Trofimovich wrote:
> 

> > To reproduce the failure we need the following system:
> > 

> > -   kernel command: page_poison=1 init_on_free=0 init_on_alloc=0
> >     

> > -   kernel config:
> >     

> >     -   CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
> >     -   CONFIG_INIT_ON_FREE_DEFAULT_ON=y
> >     -   CONFIG_PAGE_POISONING=y
> >     

> >     0000000085629bdd: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> >     

> >     0000000022861832: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> >     

> >     00000000c597f5b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> >     

> >     CPU: 11 PID: 15195 Comm: bash Kdump: loaded Tainted: G U O 5.13.1-gentoo-x86_64 #1
> >     

> >     Hardware name: System manufacturer System Product Name/PRIME Z370-A, BIOS 2801 01/13/2021
> >     

> >     Call Trace:
> >     

> >     dump_stack+0x64/0x7c
> >     

> >     __kernel_unpoison_pages.cold+0x48/0x84
> >     

> >     post_alloc_hook+0x60/0xa0
> >     

> >     get_page_from_freelist+0xdb8/0x1000
> >     

> >     __alloc_pages+0x163/0x2b0
> >     

> >     __get_free_pages+0xc/0x30
> >     

> >     pgd_alloc+0x2e/0x1a0
> >     

> >     ? dup_mm+0x37/0x4f0
> >     

> >     mm_init+0x185/0x270
> >     

> >     dup_mm+0x6b/0x4f0
> >     

> >     ? __lock_task_sighand+0x35/0x70
> >     

> >     copy_process+0x190d/0x1b10
> >     

> >     kernel_clone+0xba/0x3b0
> >     

> >     __do_sys_clone+0x8f/0xb0
> >     

> >     do_syscall_64+0x68/0x80
> >     

> >     ? do_syscall_64+0x11/0x80
> >     

> >     entry_SYSCALL_64_after_hwframe+0x44/0xae
> >     

> > 

> > Before the 51cba1eb ("init_on_alloc: Optimize static branches")
> > 

> > init_on_alloc never enabled static branch by default. It could
> > 

> > only be enabed explicitly by init_mem_debugging_and_hardening().
> 

> But init_mem_debugging_and_hardening() is always called (by mm_init()).
> 

> > But after the 51cba1eb static branch could already be enabled
> > 

> > by default. There was no code to ever disable it. That caused
> > 

> > page_poison=1 / init_on_free=1 conflict.
> > 

> > This change extends init_mem_debugging_and_hardening() to also
> > 

> > disable static branch disabling.
> > 

> > CC: Andrew Morton akpm@linux-foundation.org
> > 

> > CC: Kees Cook keescook@chromium.org
> > 

> > CC: Alexander Potapenko glider@google.com
> > 

> > CC: Thomas Gleixner tglx@linutronix.de
> > 

> > CC: Vlastimil Babka vbabka@suse.cz
> > 

> > CC: linux-mm@kvack.org
> > 

> > Reported-by: bowsingbetee@pm.me
> > 

> > Reported-by: Mikhail Morfikov
> > 

> > Fixes: 51cba1eb ("init_on_alloc: Optimize static branches")
> > 

> > Signed-off-by: Sergei Trofimovich slyfox@gentoo.org
> > -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> > 

> > mm/page_alloc.c | 16 ++++++++++------
> > 

> > 1 file changed, 10 insertions(+), 6 deletions(-)
> > 

> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > 

> > index 3b97e17806be..46cb4a9c2b50 100644
> > 

> > --- a/mm/page_alloc.c
> > 

> > +++ b/mm/page_alloc.c
> > 

> > @@ -840,18 +840,22 @@ void init_mem_debugging_and_hardening(void)
> > 

> > }
> > 

> > #endif
> > 

> > -   if (_init_on_alloc_enabled_early) {
> > -       if (page_poisoning_requested)
> >         

> >     

> > 

> > -   if (_init_on_alloc_enabled_early ||
> > -       IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON)) {
> >         

> >     

> 

> This doesn't look right. _init_on_alloc_enabled_early already has the
> 

> same value:
> 

> static bool _init_on_alloc_enabled_early __read_mostly
> 

> = IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON);
> 

> So checking this is just a side-effect of how static_branch_maybe()
> 

> happens to be behaving.
> 

> > -       if (page_poisoning_requested) {
> >         	pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
> >         		"will take precedence over init_on_alloc\\n");
> >         

> >     

> > 

> > -       else
> >         

> >     

> > 

> > -       	static_branch_disable(&init_on_alloc);
> >         

> >     

> > -       } else
> >         	static_branch_enable(&init_on_alloc);
> >         

> >     

> >     }
> > 

> > -   if (_init_on_free_enabled_early) {
> > -       if (page_poisoning_requested)
> >         

> >     

> > 

> > -   if (_init_on_free_enabled_early ||
> > -       IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON)) {
> >         

> >     

> > -       if (page_poisoning_requested) {
> >         	pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
> >         		"will take precedence over init_on_free\\n");
> >         

> >     

> > 

> > -       else
> >         

> >     

> > 

> > -       	static_branch_disable(&init_on_free);
> >         

> >     

> > -       } else
> >         	static_branch_enable(&init_on_free);
> >         

> >     

> >     }
> 

> I think it would be better to clean this up without additional
> 

> confusion involving the CONFIGs:
> 

> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> 

> index 3b97e17806be..1f19365bc158 100644
> 

> --- a/mm/page_alloc.c
> 

> +++ b/mm/page_alloc.c
> 

> @@ -840,21 +840,24 @@ void init_mem_debugging_and_hardening(void)
> 

> }
> 

> #endif
> 

> -   if (_init_on_alloc_enabled_early) {
> -         if (page_poisoning_requested)
>         

>     

> -         	pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
>         

>     

> -         		"will take precedence over init_on_alloc\\n");
>         

>     

> -         else
>         

>     

> -         	static_branch_enable(&init_on_alloc);
>         

>     

> -   }
> -   if (_init_on_free_enabled_early) {
> -         if (page_poisoning_requested)
>         

>     

> -         	pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
>         

>     

> -         		"will take precedence over init_on_free\\n");
>         

>     

> -         else
>         

>     

> -         	static_branch_enable(&init_on_free);
>         

>     

> 

> -   if ((_init_on_alloc_enabled_early || _init_on_free_enabled_early) &&
> -         page_poisoning_requested) {
>         

>     

> -         pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
>         

>     

> -         	"will take precedence over init_on_alloc and init_on_free\\n");
>         


B & C variants show this message and A does not, which is what I would expect to happen.

Tested variants:

A. "page_poison=1 init_on_free=0 init_on_alloc=0 slub_debug=P"
B. "page_poison=1 init_on_free=0 init_on_alloc=0 slub_debug=P init_on_free=1"
C. "page_poison=1 slub_debug=P"

in common:
CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
CONFIG_INIT_ON_FREE_DEFAULT_ON=y
CONFIG_PAGE_POISONING=y
CONFIG_SLUB_DEBUG=y
CONFIG_SLUB=y

(the slub parts don't matter, ignore them)

>     

> -         _init_on_alloc_enabled_early = false;
>         

>     

> -         _init_on_free_enabled_early = false;
>         

>     

>     }
> -   if (_init_on_alloc_enabled_early)
> -         static_branch_enable(&init_on_alloc);
>         

>     

> -   else
> -         static_branch_disable(&init_on_alloc);
>         

>     

> 

> -   if (_init_on_free_enabled_early)
> -         static_branch_enable(&init_on_free);
>         

>     

> -   else
> -         static_branch_disable(&init_on_free);
>         

>     

> 

> #ifdef CONFIG_DEBUG_PAGEALLOC
> 

> if (!debug_pagealloc_enabled())
> 

> return;
> 

> ------------------------------------------------------------------------
> 

> Kees Cook

While both patches(Sergei's, and yours) work for me, I'll be using this one for now.

Thank you for your work!
Cheers!


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^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction
  2021-07-14 11:11     ` bowsingbetee
@ 2021-07-14 21:14       ` Kees Cook
  0 siblings, 0 replies; 7+ messages in thread
From: Kees Cook @ 2021-07-14 21:14 UTC (permalink / raw)
  To: bowsingbetee
  Cc: Sergei Trofimovich, linux-mm, linux-kernel, Andrew Morton,
	Alexander Potapenko, Thomas Gleixner, Vlastimil Babka

On Wed, Jul 14, 2021 at 11:11:18AM +0000, bowsingbetee wrote:
> B & C variants show this message and A does not, which is what I would expect to happen.
> 
> Tested variants:
> 
> A. "page_poison=1 init_on_free=0 init_on_alloc=0 slub_debug=P"
> B. "page_poison=1 init_on_free=0 init_on_alloc=0 slub_debug=P init_on_free=1"
> C. "page_poison=1 slub_debug=P"
> 
> in common:
> CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
> CONFIG_INIT_ON_FREE_DEFAULT_ON=y
> CONFIG_PAGE_POISONING=y
> CONFIG_SLUB_DEBUG=y
> CONFIG_SLUB=y
> 
> (the slub parts don't matter, ignore them)
> 
> [...]
> 
> While both patches(Sergei's, and yours) work for me, I'll be using this one for now.
> 
> Thank you for your work!
> Cheers!

Awesome; thanks for testing it!

-Kees

-- 
Kees Cook


^ permalink raw reply	[flat|nested] 7+ messages in thread
* Re: [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction
  2021-07-14  2:00   ` Andrew Morton
@ 2021-07-17 18:18     ` Sergei Trofimovich
  0 siblings, 0 replies; 7+ messages in thread
From: Sergei Trofimovich @ 2021-07-17 18:18 UTC (permalink / raw)
  To: Andrew Morton
  Cc: linux-mm, linux-kernel, Kees Cook, Alexander Potapenko,
	Thomas Gleixner, Vlastimil Babka, bowsingbetee

On Tue, 13 Jul 2021 19:00:51 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Mon, 12 Jul 2021 22:58:16 +0100 Sergei Trofimovich <slyfox@gentoo.org> wrote:
> 
> > To reproduce the failure we need the following system:
> >   - kernel command: page_poison=1 init_on_free=0 init_on_alloc=0
> >   - kernel config:
> >     * CONFIG_INIT_ON_ALLOC_DEFAULT_ON=y
> >     * CONFIG_INIT_ON_FREE_DEFAULT_ON=y
> >     * CONFIG_PAGE_POISONING=y
> > 
> >     0000000085629bdd: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >     0000000022861832: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >     00000000c597f5b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >     CPU: 11 PID: 15195 Comm: bash Kdump: loaded Tainted: G     U     O      5.13.1-gentoo-x86_64 #1
> >     Hardware name: System manufacturer System Product Name/PRIME Z370-A, BIOS 2801 01/13/2021
> >     Call Trace:
> >      dump_stack+0x64/0x7c
> >      __kernel_unpoison_pages.cold+0x48/0x84
> >      post_alloc_hook+0x60/0xa0
> >      get_page_from_freelist+0xdb8/0x1000
> >      __alloc_pages+0x163/0x2b0
> >      __get_free_pages+0xc/0x30
> >      pgd_alloc+0x2e/0x1a0
> >      ? dup_mm+0x37/0x4f0
> >      mm_init+0x185/0x270
> >      dup_mm+0x6b/0x4f0
> >      ? __lock_task_sighand+0x35/0x70
> >      copy_process+0x190d/0x1b10
> >      kernel_clone+0xba/0x3b0
> >      __do_sys_clone+0x8f/0xb0
> >      do_syscall_64+0x68/0x80
> >      ? do_syscall_64+0x11/0x80
> >      entry_SYSCALL_64_after_hwframe+0x44/0xae
> > 
> > Before the 51cba1eb ("init_on_alloc: Optimize static branches")
> > init_on_alloc never enabled static branch by default. It could
> > only be enabed explicitly by init_mem_debugging_and_hardening().
> > 
> > But after the 51cba1eb static branch could already be enabled
> > by default. There was no code to ever disable it. That caused
> > page_poison=1 / init_on_free=1 conflict.
> > 
> > This change extends init_mem_debugging_and_hardening() to also
> > disable static branch disabling.
> > 
> > ...
> >
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -840,18 +840,22 @@ void init_mem_debugging_and_hardening(void)
> >  	}
> >  #endif
> >  
> > -	if (_init_on_alloc_enabled_early) {
> > -		if (page_poisoning_requested)
> > +	if (_init_on_alloc_enabled_early ||
> > +	    IS_ENABLED(CONFIG_INIT_ON_ALLOC_DEFAULT_ON)) {
> > +		if (page_poisoning_requested) {
> >  			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
> >  				"will take precedence over init_on_alloc\n");
> > -		else
> > +			static_branch_disable(&init_on_alloc);
> > +		} else
> >  			static_branch_enable(&init_on_alloc);
> >  	}
> > -	if (_init_on_free_enabled_early) {
> > -		if (page_poisoning_requested)
> > +	if (_init_on_free_enabled_early ||
> > +	    IS_ENABLED(CONFIG_INIT_ON_FREE_DEFAULT_ON)) {
> > +		if (page_poisoning_requested) {
> >  			pr_info("mem auto-init: CONFIG_PAGE_POISONING is on, "
> >  				"will take precedence over init_on_free\n");
> > -		else
> > +			static_branch_disable(&init_on_free);
> > +		} else
> >  			static_branch_enable(&init_on_free);
> >  	}
> >    
> 
> I'm thinking this is sufficiently serious and sufficiently reported to
> warrant a cc:stable backport.  Agree?

I agree. The patch might be tricky to apply as is too far back. But current
release should be fine.


-- 

  Sergei


^ permalink raw reply	[flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-07-17 18:20 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-11 23:57 v5.12+ regression on page_poison=1 i_on_free=0 i_on_alloc=0 warnings Sergei Trofimovich
2021-07-12 21:58 ` [PATCH] mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction Sergei Trofimovich
2021-07-14  2:00   ` Andrew Morton
2021-07-17 18:18     ` Sergei Trofimovich
2021-07-14  3:10   ` Kees Cook
2021-07-14 11:11     ` bowsingbetee
2021-07-14 21:14       ` Kees Cook

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