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AJvYcCVzac646GCWFGDSvVsqf7/0/Wr9ZhsytE5iLn0K9nIUvBGQJhRiDNHC8Nhy/OZ3ZWaX896MgGPT2w==@kvack.org X-Gm-Message-State: AOJu0YzKaxZTPr251Rs304e54vi907WeQgRt6j3xx5M++a4lPqve/UuQ f5PKyPfRZJjSVoXrTb5tXa4E/Xhktq1IuCXvhrlrhKJumFxTNLOR8V0faSrI8WKqpOkUJvWhCTK DGQ== X-Google-Smtp-Source: AGHT+IEWYcZtiY85Y5TBe4RKI/DknR4t9xSRYv397N/k2+9V5y5Th2sq2ql+LNq1WKRQLl1+RDCJRaV51A== X-Received: from lfby21.prod.google.com ([2002:a19:6415:0:b0:577:abf1:7dcc]) (user=elver job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6512:4041:b0:579:c485:8704 with SMTP id 2adb3069b0e04-579c4858934mr81687e87.42.1758204400078; Thu, 18 Sep 2025 07:06:40 -0700 (PDT) Date: Thu, 18 Sep 2025 15:59:38 +0200 In-Reply-To: <20250918140451.1289454-1-elver@google.com> Mime-Version: 1.0 References: <20250918140451.1289454-1-elver@google.com> X-Mailer: git-send-email 2.51.0.384.g4c02a37b29-goog Message-ID: <20250918140451.1289454-28-elver@google.com> Subject: [PATCH v3 27/35] kfence: Enable capability analysis From: Marco Elver To: elver@google.com, Peter Zijlstra , Boqun Feng , Ingo Molnar , Will Deacon Cc: "David S. Miller" , Luc Van Oostenryck , "Paul E. McKenney" , Alexander Potapenko , Arnd Bergmann , Bart Van Assche , Bill Wendling , Christoph Hellwig , Dmitry Vyukov , Eric Dumazet , Frederic Weisbecker , Greg Kroah-Hartman , Herbert Xu , Ian Rogers , Jann Horn , Joel Fernandes , Jonathan Corbet , Josh Triplett , Justin Stitt , Kees Cook , Kentaro Takeda , Lukas Bulwahn , Mark Rutland , Mathieu Desnoyers , Miguel Ojeda , Nathan Chancellor , Neeraj Upadhyay , Nick Desaulniers , Steven Rostedt , Tetsuo Handa , Thomas Gleixner , Thomas Graf , Uladzislau Rezki , Waiman Long , kasan-dev@googlegroups.com, linux-crypto@vger.kernel.org, linux-doc@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-sparse@vger.kernel.org, llvm@lists.linux.dev, rcu@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 222EFA000A X-Rspamd-Server: rspam05 X-Stat-Signature: yxrd3gkoe3j711qu38cig4odgt4ifn9n X-Rspam-User: X-HE-Tag: 1758204401-241320 X-HE-Meta: U2FsdGVkX18AeUC9WmeNbwFepFakXISHjD9RW+0L3XuiZB0DObNXgoyhqJENf4d1irbxIzRHndhlladKH6Yef8Ib+1tIPnnXa+VA41RZZKQ0tsbSkfCFKhQiGwyCEPqHFT8ld0hiaPZQEk14usrco2myjoRF6QrEegqm6pc/EzZtQY6abflMOidMeqfo/NZvOmUypeGNKRLFiPmXNvwKCFYLPVBf/OIsK4thf6mqj5qc55zAkMzVYL1ONxjNiUoJoncJNyb93p4jFgNpPyKSAVoDTKuyYAWSJkogCCHQPjI2U36G0Blmu3XPtukshvloPfItu6jggLv5Op3ZsnvIGaT9SKx9YAP0zUy75u5P6d+lUFrD/aHDlb/PAW8gX/GgUaC7p5M4D92cWWcS3DYUpuabrI+SrOise76P92KZkS+yNkpCjsNhZK/qT38L0FrRX7G8Jd1UrpmV1nlRljSipa4uMhdUiU+0FCbYcKpsWZXlYMFk+s4lpQmTdLXqHFZ1GIzu4mF+LHmceArxWtndCGzQ5GYm6ixDl5hj9puVE9XqYXSWomISYj9M3QfF9qQRfGGVe95r9BmhKVE79p/aBHNKWYo34bNuabdsuglHf3qVF36OaG3Hs0aAAc41zB1qyqgZKd3fMHZQAY69f9PSlDK2e+TBUwt+rSOCnmBe73sVHar/vb4wZ1o5Weqw+zr0ToXIS3Gb/uqHjdQlbt5FkWOhpGrgafljmQPOm13JhIPkLrScxD03NR7F6vT5O50c7FNpwObil9bZZDJwQS3cwoteog7W47nDY+NQfCSPJwCy2BZl4rpSwLp7fp69GP27bfmEztlEZLQ9eCC4H9B2T7fsJJgW0wghW+sSYZBYibxVdToPUSCZhPW/KACmVUwfsW9CegCmUjNNRaewDaAx12Ql1l444yoErriqI98XX3oVCC6iu+XO+lemuleBncERL14JMiEU8SPyAf7h3B2 ixFeLnqt 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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: Enable capability analysis for the KFENCE subsystem. Notable, kfence_handle_page_fault() required minor restructure, which also fixed a subtle race; arguably that function is more readable now. Signed-off-by: Marco Elver --- v2: * Remove disable/enable_capability_analysis() around headers. * Use __capability_unsafe() instead of __no_capability_analysis. --- mm/kfence/Makefile | 2 ++ mm/kfence/core.c | 20 +++++++++++++------- mm/kfence/kfence.h | 14 ++++++++------ mm/kfence/report.c | 4 ++-- 4 files changed, 25 insertions(+), 15 deletions(-) diff --git a/mm/kfence/Makefile b/mm/kfence/Makefile index 2de2a58d11a1..b3640bdc3c69 100644 --- a/mm/kfence/Makefile +++ b/mm/kfence/Makefile @@ -1,5 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 +CAPABILITY_ANALYSIS := y + obj-y := core.o report.o CFLAGS_kfence_test.o := -fno-omit-frame-pointer -fno-optimize-sibling-calls diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 0ed3be100963..53b81eb5f31a 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -132,8 +132,8 @@ struct kfence_metadata *kfence_metadata __read_mostly; static struct kfence_metadata *kfence_metadata_init __read_mostly; /* Freelist with available objects. */ -static struct list_head kfence_freelist = LIST_HEAD_INIT(kfence_freelist); -static DEFINE_RAW_SPINLOCK(kfence_freelist_lock); /* Lock protecting freelist. */ +DEFINE_RAW_SPINLOCK(kfence_freelist_lock); /* Lock protecting freelist. */ +static struct list_head kfence_freelist __guarded_by(&kfence_freelist_lock) = LIST_HEAD_INIT(kfence_freelist); /* * The static key to set up a KFENCE allocation; or if static keys are not used @@ -253,6 +253,7 @@ static bool kfence_unprotect(unsigned long addr) } static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *meta) + __must_hold(&meta->lock) { unsigned long offset = (meta - kfence_metadata + 1) * PAGE_SIZE * 2; unsigned long pageaddr = (unsigned long)&__kfence_pool[offset]; @@ -288,6 +289,7 @@ static inline bool kfence_obj_allocated(const struct kfence_metadata *meta) static noinline void metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state next, unsigned long *stack_entries, size_t num_stack_entries) + __must_hold(&meta->lock) { struct kfence_track *track = next == KFENCE_OBJECT_ALLOCATED ? &meta->alloc_track : &meta->free_track; @@ -485,7 +487,7 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g alloc_covered_add(alloc_stack_hash, 1); /* Set required slab fields. */ - slab = virt_to_slab((void *)meta->addr); + slab = virt_to_slab(addr); slab->slab_cache = cache; slab->objects = 1; @@ -514,6 +516,7 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool zombie) { struct kcsan_scoped_access assert_page_exclusive; + u32 alloc_stack_hash; unsigned long flags; bool init; @@ -546,9 +549,10 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z /* Mark the object as freed. */ metadata_update_state(meta, KFENCE_OBJECT_FREED, NULL, 0); init = slab_want_init_on_free(meta->cache); + alloc_stack_hash = meta->alloc_stack_hash; raw_spin_unlock_irqrestore(&meta->lock, flags); - alloc_covered_add(meta->alloc_stack_hash, -1); + alloc_covered_add(alloc_stack_hash, -1); /* Check canary bytes for memory corruption. */ check_canary(meta); @@ -593,6 +597,7 @@ static void rcu_guarded_free(struct rcu_head *h) * which partial initialization succeeded. */ static unsigned long kfence_init_pool(void) + __capability_unsafe(/* constructor */) { unsigned long addr; struct page *pages; @@ -1192,6 +1197,7 @@ bool kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs { const int page_index = (addr - (unsigned long)__kfence_pool) / PAGE_SIZE; struct kfence_metadata *to_report = NULL; + unsigned long unprotected_page = 0; enum kfence_error_type error_type; unsigned long flags; @@ -1225,9 +1231,8 @@ bool kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs if (!to_report) goto out; - raw_spin_lock_irqsave(&to_report->lock, flags); - to_report->unprotected_page = addr; error_type = KFENCE_ERROR_OOB; + unprotected_page = addr; /* * If the object was freed before we took the look we can still @@ -1239,7 +1244,6 @@ bool kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs if (!to_report) goto out; - raw_spin_lock_irqsave(&to_report->lock, flags); error_type = KFENCE_ERROR_UAF; /* * We may race with __kfence_alloc(), and it is possible that a @@ -1251,6 +1255,8 @@ bool kfence_handle_page_fault(unsigned long addr, bool is_write, struct pt_regs out: if (to_report) { + raw_spin_lock_irqsave(&to_report->lock, flags); + to_report->unprotected_page = unprotected_page; kfence_report_error(addr, is_write, regs, to_report, error_type); raw_spin_unlock_irqrestore(&to_report->lock, flags); } else { diff --git a/mm/kfence/kfence.h b/mm/kfence/kfence.h index dfba5ea06b01..f9caea007246 100644 --- a/mm/kfence/kfence.h +++ b/mm/kfence/kfence.h @@ -34,6 +34,8 @@ /* Maximum stack depth for reports. */ #define KFENCE_STACK_DEPTH 64 +extern raw_spinlock_t kfence_freelist_lock; + /* KFENCE object states. */ enum kfence_object_state { KFENCE_OBJECT_UNUSED, /* Object is unused. */ @@ -53,7 +55,7 @@ struct kfence_track { /* KFENCE metadata per guarded allocation. */ struct kfence_metadata { - struct list_head list; /* Freelist node; access under kfence_freelist_lock. */ + struct list_head list __guarded_by(&kfence_freelist_lock); /* Freelist node. */ struct rcu_head rcu_head; /* For delayed freeing. */ /* @@ -91,13 +93,13 @@ struct kfence_metadata { * In case of an invalid access, the page that was unprotected; we * optimistically only store one address. */ - unsigned long unprotected_page; + unsigned long unprotected_page __guarded_by(&lock); /* Allocation and free stack information. */ - struct kfence_track alloc_track; - struct kfence_track free_track; + struct kfence_track alloc_track __guarded_by(&lock); + struct kfence_track free_track __guarded_by(&lock); /* For updating alloc_covered on frees. */ - u32 alloc_stack_hash; + u32 alloc_stack_hash __guarded_by(&lock); #ifdef CONFIG_MEMCG struct slabobj_ext obj_exts; #endif @@ -141,6 +143,6 @@ enum kfence_error_type { void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *regs, const struct kfence_metadata *meta, enum kfence_error_type type); -void kfence_print_object(struct seq_file *seq, const struct kfence_metadata *meta); +void kfence_print_object(struct seq_file *seq, const struct kfence_metadata *meta) __must_hold(&meta->lock); #endif /* MM_KFENCE_KFENCE_H */ diff --git a/mm/kfence/report.c b/mm/kfence/report.c index 10e6802a2edf..787e87c26926 100644 --- a/mm/kfence/report.c +++ b/mm/kfence/report.c @@ -106,6 +106,7 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries static void kfence_print_stack(struct seq_file *seq, const struct kfence_metadata *meta, bool show_alloc) + __must_hold(&meta->lock) { const struct kfence_track *track = show_alloc ? &meta->alloc_track : &meta->free_track; u64 ts_sec = track->ts_nsec; @@ -207,8 +208,6 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r if (WARN_ON(type != KFENCE_ERROR_INVALID && !meta)) return; - if (meta) - lockdep_assert_held(&meta->lock); /* * Because we may generate reports in printk-unfriendly parts of the * kernel, such as scheduler code, the use of printk() could deadlock. @@ -263,6 +262,7 @@ void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *r stack_trace_print(stack_entries + skipnr, num_stack_entries - skipnr, 0); if (meta) { + lockdep_assert_held(&meta->lock); pr_err("\n"); kfence_print_object(NULL, meta); } -- 2.51.0.384.g4c02a37b29-goog