From nobody Fri May 17 11:05:30 2024 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 13FE0E54C; Wed, 17 Apr 2024 03:27:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.188 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713324471; cv=none; b=lE8bRdNXHxD/qhlKq37qbYRyw4ACwZKWnq0FgvV5WbhR+6bOxlRf/qRMXwWp9HulDUWjssyV/3tn1LxVbwRr2aK6XkAiRN/NrryOGQGZ2REnu8oLlKRE4l6pnd4NR3N5QvEpMt9c+h+B4KXAHDoUy3U61KAh8ylPGekHjOWY9Q8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713324471; c=relaxed/simple; bh=r4KiFE+z6Yjl+E0UrlArfx0WhhGiKdnxIypFv3feVE8=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=i1ssXyW7UeDYRxpFkoylZ2ykHlemk5sfKZb4lnO6MslPUVBM0mHZxFjIpF1ddmJxKKBy+81IBSiRzRQYp4haMHSx10EF7qnBj2mr1gX/ITeedvU5MVny0PYmOTc0fshm7p8FiTXnM+XI+DBZ3yyo3gJbUd1oVfqgHUzVaglgVyw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.163.252]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4VK5tF1ztvzYdQ8; Wed, 17 Apr 2024 11:26:45 +0800 (CST) Received: from dggpeml500012.china.huawei.com (unknown [7.185.36.15]) by mail.maildlp.com (Postfix) with ESMTPS id 7EB1E18006D; Wed, 17 Apr 2024 11:27:46 +0800 (CST) Received: from localhost.localdomain (10.67.175.61) by dggpeml500012.china.huawei.com (7.185.36.15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.35; Wed, 17 Apr 2024 11:27:46 +0800 From: Zheng Yejian To: , , , CC: , , , Subject: [PATCH v3] ftrace: Fix possible use-after-free issue in ftrace_location() Date: Wed, 17 Apr 2024 11:28:30 +0800 Message-ID: <20240417032830.1764690-1-zhengyejian1@huawei.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240401125543.1282845-1-zhengyejian1@huawei.com> References: <20240401125543.1282845-1-zhengyejian1@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpeml500012.china.huawei.com (7.185.36.15) Content-Type: text/plain; charset="utf-8" KASAN reports a bug: BUG: KASAN: use-after-free in ftrace_location+0x90/0x120 Read of size 8 at addr ffff888141d40010 by task insmod/424 CPU: 8 PID: 424 Comm: insmod Tainted: G W 6.9.0-rc2+ [...] Call Trace: dump_stack_lvl+0x68/0xa0 print_report+0xcf/0x610 kasan_report+0xb5/0xe0 ftrace_location+0x90/0x120 register_kprobe+0x14b/0xa40 kprobe_init+0x2d/0xff0 [kprobe_example] do_one_initcall+0x8f/0x2d0 do_init_module+0x13a/0x3c0 load_module+0x3082/0x33d0 init_module_from_file+0xd2/0x130 __x64_sys_finit_module+0x306/0x440 do_syscall_64+0x68/0x140 entry_SYSCALL_64_after_hwframe+0x71/0x79 The root cause is that, in lookup_rec(), ftrace record of some address is being searched in ftrace pages of some module, but those ftrace pages at the same time is being freed in ftrace_release_mod() as the corresponding module is being deleted: CPU1 | CPU2 register_kprobes() { | delete_module() { check_kprobe_address_safe() { | arch_check_ftrace_location() { | ftrace_location() { | lookup_rec() // USE! | ftrace_release_mod() // Free! To fix this issue: 1. Hold rcu lock as accessing ftrace pages in ftrace_location_range(); 2. Use ftrace_location_range() instead of lookup_rec() in ftrace_location(); 3. Call synchronize_rcu() before freeing any ftrace pages both in ftrace_process_locs()/ftrace_release_mod()/ftrace_free_mem(). Fixes: ae6aa16fdc16 ("kprobes: introduce ftrace based optimization") Suggested-by: Steven Rostedt Signed-off-by: Zheng Yejian --- kernel/trace/ftrace.c | 46 ++++++++++++++++++++++++++++--------------- 1 file changed, 30 insertions(+), 16 deletions(-) v3: - Complete the commit description and add Suggested-by tag - Add comments around where synchronize_rcu() is called v2: - Link: https://lore.kernel.org/all/20240416112459.1444612-1-zhengyejian1@= huawei.com/ - Use RCU lock instead of holding ftrace_lock as suggested by Steve. Link: https://lore.kernel.org/all/20240410112823.1d084c8f@gandalf.local.= home/ v1: - Link: https://lore.kernel.org/all/20240401125543.1282845-1-zhengyejian1@= huawei.com/ diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index da1710499698..e05d3e3dc06a 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1581,7 +1581,7 @@ static struct dyn_ftrace *lookup_rec(unsigned long st= art, unsigned long end) } =20 /** - * ftrace_location_range - return the first address of a traced location + * ftrace_location_range_rcu - return the first address of a traced locati= on * if it touches the given ip range * @start: start of range to search. * @end: end of range to search (inclusive). @end points to the last byte @@ -1592,7 +1592,7 @@ static struct dyn_ftrace *lookup_rec(unsigned long st= art, unsigned long end) * that is either a NOP or call to the function tracer. It checks the ftra= ce * internal tables to determine if the address belongs or not. */ -unsigned long ftrace_location_range(unsigned long start, unsigned long end) +static unsigned long ftrace_location_range_rcu(unsigned long start, unsign= ed long end) { struct dyn_ftrace *rec; =20 @@ -1603,6 +1603,16 @@ unsigned long ftrace_location_range(unsigned long st= art, unsigned long end) return 0; } =20 +unsigned long ftrace_location_range(unsigned long start, unsigned long end) +{ + unsigned long loc; + + rcu_read_lock(); + loc =3D ftrace_location_range_rcu(start, end); + rcu_read_unlock(); + return loc; +} + /** * ftrace_location - return the ftrace location * @ip: the instruction pointer to check @@ -1614,25 +1624,22 @@ unsigned long ftrace_location_range(unsigned long s= tart, unsigned long end) */ unsigned long ftrace_location(unsigned long ip) { - struct dyn_ftrace *rec; + unsigned long loc; unsigned long offset; unsigned long size; =20 - rec =3D lookup_rec(ip, ip); - if (!rec) { + loc =3D ftrace_location_range(ip, ip); + if (!loc) { if (!kallsyms_lookup_size_offset(ip, &size, &offset)) goto out; =20 /* map sym+0 to __fentry__ */ if (!offset) - rec =3D lookup_rec(ip, ip + size - 1); + loc =3D ftrace_location_range(ip, ip + size - 1); } =20 - if (rec) - return rec->ip; - out: - return 0; + return loc; } =20 /** @@ -6596,6 +6603,8 @@ static int ftrace_process_locs(struct module *mod, /* We should have used all pages unless we skipped some */ if (pg_unuse) { WARN_ON(!skipped); + /* Need to synchronize with ftrace_location_range() */ + synchronize_rcu(); ftrace_free_pages(pg_unuse); } return ret; @@ -6809,6 +6818,9 @@ void ftrace_release_mod(struct module *mod) out_unlock: mutex_unlock(&ftrace_lock); =20 + /* Need to synchronize with ftrace_location_range() */ + if (tmp_page) + synchronize_rcu(); for (pg =3D tmp_page; pg; pg =3D tmp_page) { =20 /* Needs to be called outside of ftrace_lock */ @@ -7142,6 +7154,7 @@ void ftrace_free_mem(struct module *mod, void *start_= ptr, void *end_ptr) unsigned long start =3D (unsigned long)(start_ptr); unsigned long end =3D (unsigned long)(end_ptr); struct ftrace_page **last_pg =3D &ftrace_pages_start; + struct ftrace_page *tmp_page =3D NULL; struct ftrace_page *pg; struct dyn_ftrace *rec; struct dyn_ftrace key; @@ -7183,12 +7196,8 @@ void ftrace_free_mem(struct module *mod, void *start= _ptr, void *end_ptr) ftrace_update_tot_cnt--; if (!pg->index) { *last_pg =3D pg->next; - if (pg->records) { - free_pages((unsigned long)pg->records, pg->order); - ftrace_number_of_pages -=3D 1 << pg->order; - } - ftrace_number_of_groups--; - kfree(pg); + pg->next =3D tmp_page; + tmp_page =3D pg; pg =3D container_of(last_pg, struct ftrace_page, next); if (!(*last_pg)) ftrace_pages =3D pg; @@ -7205,6 +7214,11 @@ void ftrace_free_mem(struct module *mod, void *start= _ptr, void *end_ptr) clear_func_from_hashes(func); kfree(func); } + /* Need to synchronize with ftrace_location_range() */ + if (tmp_page) { + synchronize_rcu(); + ftrace_free_pages(tmp_page); + } } =20 void __init ftrace_free_init_mem(void) --=20 2.25.1