‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Wednesday, July 14th, 2021 at 5:10 AM, Kees Cook 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!