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Tue, 2 Dec 2025 10:59:54 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id RdDNNqrGLmnNNQAAD6G6ig (envelope-from ); Tue, 02 Dec 2025 10:59:54 +0000 Message-ID: <127ca65a-bc74-4554-b0bd-f75ea2d099bb@suse.cz> Date: Tue, 2 Dec 2025 11:59:55 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/mm_init: Introduce a boot parameter for check_pages To: Joshua Hahn , Andrew Morton Cc: SeongJae Park , Jonathan Corbet , Mike Rapoport , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com References: <20251201180739.2330474-1-joshua.hahnjy@gmail.com> From: Vlastimil Babka Content-Language: en-US In-Reply-To: <20251201180739.2330474-1-joshua.hahnjy@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: B79831C0007 X-Rspamd-Server: rspam06 X-Rspam-User: X-Stat-Signature: ryjmdsont46x4oda5nziae4o1cmng3h4 X-HE-Tag: 1764673196-845449 X-HE-Meta: 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 ok7DmdEu 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 12/1/25 7:07 PM, Joshua Hahn wrote: > Use-after-free and double-free bugs can be very difficult to track down. > The kernel is good at tracking these and preventing bad pages from being > used/created through simple checks gated behind "check_pages_enabled". > > Currently, the only ways to enable this flag is by building with > CONFIG_DEBUG_VM, or as a side effect of other checks such as > init_on_{alloc, free}, page_poisoning, or debug_pagealloc among others. > These solutions are powerful, but may often be too coarse in balancing > the performance vs. safety that a user may want, particularly in > latency-sensitive production environments. > > Introduce a new boot parameter "check_pages", which enables page checking > with no other side effects. It takes kstrbool-able inputs as an argument > (i.e. 0/1, true/false, on/off, ...). This patch is backwards-compatible; > setting CONFIG_DEBUG_VM still enables page checking. > > Acked-by: SeongJae Park > Acked-by: Michal Hocko > Signed-off-by: Joshua Hahn Acked-by: Vlastimil Babka Thanks! > --- > v2 --> v3: > - Dropped the second patch. I may pursue it at another time : -) > - Variable renaming (dropping leading _) and cleaner check in > mem_debugging_and_hardening_init, as suggested by Mike Rapoport > v1 --> v2: > - Changed check_pages from a build config into a boot config, as suggested > by Vlastimil. > - Introduced the second patch, which decouples page checking from > init_on_page_alloc and init_on_page_free. > --- > Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++ > mm/mm_init.c | 10 +++++++++- > 2 files changed, 17 insertions(+), 1 deletion(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 6c42061ca20e..acdc7fbdecac 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -669,6 +669,14 @@ > nokmem -- Disable kernel memory accounting. > nobpf -- Disable BPF memory accounting. > > + check_pages= [MM,EARLY] Enable sanity checking of pages after > + allocations / before freeing. This adds checks to catch > + double-frees, use-after-frees, and other sources of > + page corruption by inspecting page internals (flags, > + mapcount/refcount, memcg_data, etc.). > + Format: { "0" | "1" } > + Default: 0 (1 if CONFIG_DEBUG_VM is set) > + > checkreqprot= [SELINUX] Set initial checkreqprot flag value. > Format: { "0" | "1" } > See security/selinux/Kconfig help text. > diff --git a/mm/mm_init.c b/mm/mm_init.c > index c6812b4dbb2e..fc2a6f1e518f 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -2525,6 +2525,14 @@ early_param("init_on_free", early_init_on_free); > > DEFINE_STATIC_KEY_MAYBE(CONFIG_DEBUG_VM, check_pages_enabled); > > +static bool check_pages_enabled_early __initdata; > + > +static int __init early_check_pages(char *buf) > +{ > + return kstrtobool(buf, &check_pages_enabled_early); > +} > +early_param("check_pages", early_check_pages); > + > /* > * Enable static keys related to various memory debugging and hardening options. > * Some override others, and depend on early params that are evaluated in the > @@ -2534,7 +2542,7 @@ DEFINE_STATIC_KEY_MAYBE(CONFIG_DEBUG_VM, check_pages_enabled); > static void __init mem_debugging_and_hardening_init(void) > { > bool page_poisoning_requested = false; > - bool want_check_pages = false; > + bool want_check_pages = check_pages_enabled_early; > > #ifdef CONFIG_PAGE_POISONING > /*