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Wed, 24 Sep 2025 04:52:07 -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 09/23] mm/ksw: ignore false positives from exit trampolines Date: Wed, 24 Sep 2025 19:50:52 +0800 Message-ID: <20250924115124.194940-10-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: rspam06 X-Rspamd-Queue-Id: 1156A180012 X-Stat-Signature: auqo4p37hqz8ebbmibhm7bswpqp9dy8g X-HE-Tag: 1758714728-302572 X-HE-Meta: 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 N7+2W634 14ph8hlWP9hWxOBpWajktAei7XoB1+snMvP4vrEe8RZxSQ6jJAglVd7Ei9Xcfn7b5lwv7i5fV/vUwSm3+cSK8LAZm0LAmwlDr9AhreL1XYOcJCs2vk6uYmYD0aWDUTczu+szQU+Sw4+koa0oxWmDyfESmFl9VZk8Gn3PYfe7NeieX6SHUZhfXYz1QyeACa+r0oBC4bAmghCrlGiMxcm3azwPOAg== 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: Because trampolines run after the watched function returns but before the exit_handler is called, and in the original stack frame, so the trampoline code may overwrite the watched stack address. These false positives should be ignored. is_ftrace_trampoline() does not cover all trampolines, so add a local check to handle the remaining cases. Signed-off-by: Jinchao Wang --- mm/kstackwatch/watch.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/mm/kstackwatch/watch.c b/mm/kstackwatch/watch.c index 887cc13292dc..722ffd9fda7c 100644 --- a/mm/kstackwatch/watch.c +++ b/mm/kstackwatch/watch.c @@ -2,6 +2,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include +#include #include #include #include @@ -18,10 +19,46 @@ bool panic_on_catch; module_param(panic_on_catch, bool, 0644); MODULE_PARM_DESC(panic_on_catch, "panic immediately on corruption catch"); +#define TRAMPOLINE_NAME "return_to_handler" +#define TRAMPOLINE_DEPTH 16 + +/* Resolved once, then reused */ +static unsigned long tramp_start, tramp_end; + +static void ksw_watch_resolve_trampoline(void) +{ + unsigned long sz, off; + + if (likely(tramp_start && tramp_end)) + return; + + tramp_start = kallsyms_lookup_name(TRAMPOLINE_NAME); + if (tramp_start && kallsyms_lookup_size_offset(tramp_start, &sz, &off)) + tramp_end = tramp_start + sz; +} + +static bool ksw_watch_in_trampoline(unsigned long ip) +{ + if (tramp_start && tramp_end && ip >= tramp_start && ip < tramp_end) + return true; + return false; +} static void ksw_watch_handler(struct perf_event *bp, struct perf_sample_data *data, struct pt_regs *regs) { + unsigned long entries[TRAMPOLINE_DEPTH]; + int i, nr = 0; + + nr = stack_trace_save_regs(regs, entries, TRAMPOLINE_DEPTH, 0); + for (i = 0; i < nr; i++) { + //ignore trampoline + if (is_ftrace_trampoline(entries[i])) + return; + if (ksw_watch_in_trampoline(entries[i])) + return; + } + pr_err("========== KStackWatch: Caught stack corruption =======\n"); pr_err("config %s\n", ksw_get_config()->user_input); dump_stack(); @@ -168,6 +205,7 @@ int ksw_watch_init(void) { int ret; + ksw_watch_resolve_trampoline(); ret = ksw_watch_alloc(); if (ret <= 0) return -EBUSY; -- 2.43.0