From: Josh Poimboeuf Date: Thu, 6 Aug 2026 04:56:46 +0000 (-0700) Subject: ftrace: Fix off-by-one fentry site disable in ftrace_free_mem() X-Git-Tag: v7.2-rc7~1^2~4 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=8b8292d6487c81bd57c2605a9b404b1cf8f1edfb;p=thirdparty%2Flinux.git ftrace: Fix off-by-one fentry site disable in ftrace_free_mem() When a module's init text is freed, do_init_module() calls ftrace_free_mem() with a half-open [start, end) range. However the ftrace_cmp_recs() comparator treats the upper bound as inclusive, as all its other users do, passing 'ip + size - 1'. So ftrace_free_mem() can delete a record sitting exactly at 'end', which is outside the freed range. For a kernel without CFI or IBT, the first record of a function is at the function start, which for the first function in a module is also the base of its text allocation. As the module allocator packs its regions, that address is often the 'end' passed by a neighboring module's do_init_module(), causing the first function's ftrace location to get disabled, preventing an attempt to livepatch it: livepatch: failed to find location for function 'pcspkr_probe' Convert the exclusive end to the inclusive 'end - 1' the comparator expects, and return early for an empty range to avoid the subtraction from underflowing when the init text size is zero. Cc: stable@vger.kernel.org Fixes: 42c269c88dc1 ("ftrace: Allow for function tracing to record init functions on boot up") Link: https://patch.msgid.link/1b5ccfa8095bdb1277f84af1c2c2e2205aca03ae.1785992188.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt --- diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 414e425c2d80..7c50f8ae5a0c 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -8305,7 +8305,8 @@ static void add_to_clear_hash_list(struct list_head *clear_list, void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr) { unsigned long start = (unsigned long)(start_ptr); - unsigned long end = (unsigned long)(end_ptr); + /* end is inclusive and end_ptr is exclusive */ + unsigned long end = (unsigned long)(end_ptr) - 1; struct ftrace_page **last_pg = &ftrace_pages_start; struct ftrace_page *tmp_page = NULL; struct ftrace_page *pg; @@ -8315,6 +8316,9 @@ void ftrace_free_mem(struct module *mod, void *start_ptr, void *end_ptr) struct ftrace_init_func *func, *func_next; LIST_HEAD(clear_hash); + if (start_ptr >= end_ptr) + return; + key.ip = start; key.flags = end; /* overload flags, as it is unsigned long */