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Thu, 09 Oct 2025 03:58:02 -0700 (PDT) From: Jinchao Wang To: Andrew Morton , Masami Hiramatsu , Peter Zijlstra , Mike Rapoport , Alexander Potapenko , Randy Dunlap , Marco Elver , Jonathan Corbet , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. 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Miller" , Mathieu Desnoyers , linux-trace-kernel@vger.kernel.org Cc: Jinchao Wang Subject: [PATCH v7 14/23] mm/ksw: resolve stack watch addr and len Date: Thu, 9 Oct 2025 18:55:50 +0800 Message-ID: <20251009105650.168917-15-wangjinchao600@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251009105650.168917-1-wangjinchao600@gmail.com> References: <20251009105650.168917-1-wangjinchao600@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: mmcem3g3yzz9qosu85ifhhkzzeq7dsm9 X-Rspamd-Queue-Id: 1761E180005 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1760007483-177753 X-HE-Meta: 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 bRRlKfQP 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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: 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 | 77 ++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 74 insertions(+), 3 deletions(-) diff --git a/mm/kstackwatch/stack.c b/mm/kstackwatch/stack.c index e596ef97222d..3c4cb6d5b58a 100644 --- a/mm/kstackwatch/stack.c +++ b/mm/kstackwatch/stack.c @@ -9,6 +9,7 @@ #include "kstackwatch.h" +#define MAX_CANARY_SEARCH_STEPS 128 static struct kprobe entry_probe; static struct fprobe exit_probe; @@ -59,13 +60,83 @@ 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; + + // default is to watch the canary + if (!ksw_get_config()->watch_len) { + addr = ksw_find_stack_canary_addr(regs); + len = sizeof(ulong); + } else { + addr = kernel_stack_pointer(regs) + ksw_get_config()->sp_offset; + len = ksw_get_config()->watch_len; + } + + 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