The patch titled Subject: mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction has been added to the -mm tree. Its filename is mm-page_alloc-fix-page_poison=1-init_on_alloc_default_on-interaction.patch

This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-fix-page_poison%3D1-... and later at https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-fix-page_poison%3D1-...

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------------------------------------------------------ From: Sergei Trofimovich slyfox@gentoo.org Subject: mm: page_alloc: fix page_poison=1 / INIT_ON_ALLOC_DEFAULT_ON interaction

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.

Link: https://lkml.kernel.org/r/20210712215816.1512739-1-slyfox@gentoo.org Fixes: 51cba1eb ("init_on_alloc: Optimize static branches") Signed-off-by: Sergei Trofimovich slyfox@gentoo.org Reported-by: bowsingbetee@pm.me Reported-by: Mikhail Morfikov 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: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/page_alloc.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-)

--- a/mm/page_alloc.c~mm-page_alloc-fix-page_poison=1-init_on_alloc_default_on-interaction +++ a/mm/page_alloc.c @@ -840,18 +840,22 @@ void init_mem_debugging_and_hardening(vo } #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); }

_

Patches currently in -mm which might be from slyfox@gentoo.org are

mm-page_alloc-fix-page_poison=1-init_on_alloc_default_on-interaction.patch