On Tue, 13 Jul 2021 19:00:51 -0700
Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 12 Jul 2021 22:58:16 +0100 Sergei Trofimovich <slyfox@xxxxxxxxxx> 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
