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Wed, 24 Sep 2025 04:52:25 -0700 (PDT) From: Jinchao Wang To: Andrew Morton , Masami Hiramatsu , Peter Zijlstra , Mike Rapoport , Alexander Potapenko , Randy Dunlap , 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 v5 14/23] mm/ksw: resolve stack watch addr and len Date: Wed, 24 Sep 2025 19:50:57 +0800 Message-ID: <20250924115124.194940-15-wangjinchao600@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250924115124.194940-1-wangjinchao600@gmail.com> References: <20250924115124.194940-1-wangjinchao600@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 823F314000A X-Stat-Signature: 5z9wbgahox5111t1gims1di6tg8dbqth X-HE-Tag: 1758714747-677536 X-HE-Meta: U2FsdGVkX19IvF7nwUeWd1+F2QUNhKMhCxlkE+Yv7e38RJb7aR1BDcQ6JwGssqGgt0HEqcwB4J4I/hkD6v788j1Zhslt8FUa6zeNHKcf8huJDmqeqD1YWHbVPEQFkx6D1HysPn4hECKLsxijXim4DK5VyI/Aku+aJkWIufbq4gZ9zJnxzajW8TdQIGXjq7uOTzgDNsoFMbPvtz/GhhCO5kcbdUcCErFFOIBaCXOTaFVavrwxEEBt7Oi/YFtSEzRCMkEZYdWobdd9olbqNdKcbNxksoZyOBPNM6ZUPLrBPHeLoCtDHgfVlemSy7iu5XshxF6QDZRQZVJ9so7j0sF140V81nNgjXZKqTkmXm0+IBYpxxhwQ0FeWnBWlzzy71CB28R8eBwpdBUNgAMDGP/65c3mRb5S3U4kJ5221ESA3ugCYM3/Ov4eviuaqtPB9ac0iB50xV90hCsOar7U8wHWSWpGOjyvorp9zdBtmR8A6W5kWd+XutMkUXDCS4tU57DdZH0N/Ts3yYnjrGxlHLDo6RnvoTHDienrZ+pG7AgHypVvIvLJ7t2ZvtYyUXwxU44dEG5U3L0daqp7V9+FDzZu2TVhNkfZDryJ2pWzdCtb9TFSEhEMktL3AGa1R+6HeJTBCrZ7HfgLYc0z+fXhVsYxNGPfISTt3Ja2SWjjgngPVtS2oBs2WyRqTdLUDxRk+B1FFCpsMoZUxzG+jeEfRiylusCtjp1qadikQIV71bTt3r6IKrHB4WwH/cplItEzkkxcscsTC6+IB63IP+1v8mYRLOSSuqvgfl1kLTtzcukm2Yh4OzqlfB9sRSzCV6Dw/CWLfA1xFstlLcBBkGbjWfgqIZhwTOT5CiAVi7P5kignZHL57AszE+DRHIWx3XOLG+DQ8bBqnwRVTRQAGrpQem3dxW8g9hhwBc/Gova+1L6r3yRtDLML9ujsKkZqK/AF/SrqF0SE9Ts+3NSxlN+O/xT KiqVRhm+ 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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