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Miller" , Dietmar Eggemann , Dmitry Vyukov , "H. Peter Anvin" , Ian Rogers , Ingo Molnar , James Clark , Jinchao Wang , Jinjie Ruan , Jiri Olsa , Jonathan Corbet , Juri Lelli , Justin Stitt , kasan-dev@googlegroups.com, Kees Cook , "Liam R. Howlett" , "Liang Kan" , Linus Walleij , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-perf-users@vger.kernel.org, linux-trace-kernel@vger.kernel.org, llvm@lists.linux.dev, Lorenzo Stoakes , Mark Rutland , Masahiro Yamada , Mathieu Desnoyers , Mel Gorman , Michal Hocko , Miguel Ojeda , Nam Cao , Namhyung Kim , Nathan Chancellor , Naveen N Rao , Nick Desaulniers , Rong Xu , Sami Tolvanen , Steven Rostedt , Suren Baghdasaryan , Thomas Gleixner , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Valentin Schneider , Vincent Guittot , Vincenzo Frascino , Vlastimil Babka , Will Deacon , workflows@vger.kernel.org, x86@kernel.org Subject: [PATCH v8 14/27] mm/ksw: resolve stack watch addr and len Date: Tue, 11 Nov 2025 00:36:09 +0800 Message-ID: <20251110163634.3686676-15-wangjinchao600@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251110163634.3686676-1-wangjinchao600@gmail.com> References: <20251110163634.3686676-1-wangjinchao600@gmail.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add helpers to find the stack canary or a local variable addr and len for the probed function based on ksw_get_config(). For canary search, limits search to a fixed number of steps to avoid scanning the entire stack. Validates that the computed address and length are within the kernel stack. Signed-off-by: Jinchao Wang --- mm/kstackwatch/stack.c | 80 ++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 77 insertions(+), 3 deletions(-) diff --git a/mm/kstackwatch/stack.c b/mm/kstackwatch/stack.c index 96014eb4cb12..60371b292915 100644 --- a/mm/kstackwatch/stack.c +++ b/mm/kstackwatch/stack.c @@ -8,6 +8,7 @@ #include #include +#define MAX_CANARY_SEARCH_STEPS 128 static struct kprobe entry_probe; static struct fprobe exit_probe; @@ -58,13 +59,86 @@ static bool ksw_stack_check_ctx(bool entry) return false; } +static unsigned long ksw_find_stack_canary_addr(struct pt_regs *regs) +{ + unsigned long *stack_ptr, *stack_end, *stack_base; + unsigned long expected_canary; + unsigned int i; + + stack_ptr = (unsigned long *)kernel_stack_pointer(regs); + + stack_base = (unsigned long *)(current->stack); + + // TODO: limit it to the current frame + stack_end = (unsigned long *)((char *)current->stack + THREAD_SIZE); + + expected_canary = current->stack_canary; + + if (stack_ptr < stack_base || stack_ptr >= stack_end) { + pr_err("Stack pointer 0x%lx out of bounds [0x%lx, 0x%lx)\n", + (unsigned long)stack_ptr, (unsigned long)stack_base, + (unsigned long)stack_end); + return 0; + } + + for (i = 0; i < MAX_CANARY_SEARCH_STEPS; i++) { + if (&stack_ptr[i] >= stack_end) + break; + + if (stack_ptr[i] == expected_canary) { + pr_debug("canary found i:%d 0x%lx\n", i, + (unsigned long)&stack_ptr[i]); + return (unsigned long)&stack_ptr[i]; + } + } + + pr_debug("canary not found in first %d steps\n", + MAX_CANARY_SEARCH_STEPS); + return 0; +} + +static int ksw_stack_validate_addr(unsigned long addr, size_t size) +{ + unsigned long stack_start, stack_end; + + if (!addr || !size) + return -EINVAL; + + stack_start = (unsigned long)current->stack; + stack_end = stack_start + THREAD_SIZE; + + if (addr < stack_start || (addr + size) > stack_end) + return -ERANGE; + + return 0; +} + static int ksw_stack_prepare_watch(struct pt_regs *regs, const struct ksw_config *config, ulong *watch_addr, u16 *watch_len) { - /* implement logic will be added in following patches */ - *watch_addr = 0; - *watch_len = 0; + ulong addr; + u16 len; + + if (ksw_get_config()->auto_canary) { + addr = ksw_find_stack_canary_addr(regs); + if (!addr) + return -EINVAL; + len = sizeof(ulong); + } else { + addr = kernel_stack_pointer(regs) + ksw_get_config()->sp_offset; + len = ksw_get_config()->watch_len; + if (!len) + len = sizeof(ulong); + } + + if (ksw_stack_validate_addr(addr, len)) { + pr_err("invalid stack addr:0x%lx len :%u\n", addr, len); + return -EINVAL; + } + + *watch_addr = addr; + *watch_len = len; return 0; } -- 2.43.0