From nobody Wed Feb 11 04:17:42 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 6CB1B1802A2; Tue, 14 May 2024 16:14:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715703298; cv=none; b=FkIZaOt1FuP9nWFE+OMMrGu7duM9x21601BxBSehEuG1tEyhGs8VNVXUjh8/zWxG524E1rSgqrv39C7hvSXQlpuYv1mSlz+55c8vH6hGs1sq54dldibVvGrVXQPI6BvlGhLb+iHNy3D+zBf2ljw/NGqE77hPMBs1SCgVmoTakLA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715703298; c=relaxed/simple; bh=7I3klhPaxuAupmowkpMOzMleftgrCHK6TCFtEIWDYrk=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=EaFaqxoQCOiO7eSQiTk1uD+w8ud+jg9vdWLkkRog02V3c49uqx3yxb74Hl1icJbcZ0/QoJturUscjr0vL08fLNK7Xs31/zeoDq/eYQ92hoHOqvShAq/QZuzEm4E1v/WW1wNXHZ4aIVK4vG8Kdv8DIxDRAbHLkOOCYETKrv5UarI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51BAAC4DDE2; Tue, 14 May 2024 16:14:58 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1s6uoE-00000003t5Q-3wZA; Tue, 14 May 2024 12:15:22 -0400 Message-ID: <20240514161522.796744802@goodmis.org> User-Agent: quilt/0.68 Date: Tue, 14 May 2024 12:14:44 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , stable@vger.kernel.org, Zheng Yejian Subject: [for-next][PATCH 6/7] ftrace: Fix possible use-after-free issue in ftrace_location() References: <20240514161438.134250861@goodmis.org> 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 Content-Type: text/plain; charset="utf-8" From: Zheng Yejian 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(). Link: https://lore.kernel.org/linux-trace-kernel/20240509192859.1273558-1-z= hengyejian1@huawei.com Cc: stable@vger.kernel.org Cc: Cc: Cc: Fixes: ae6aa16fdc16 ("kprobes: introduce ftrace based optimization") Suggested-by: Steven Rostedt Signed-off-by: Zheng Yejian Signed-off-by: Steven Rostedt (Google) --- kernel/trace/ftrace.c | 39 +++++++++++++++++++++++---------------- 1 file changed, 23 insertions(+), 16 deletions(-) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 5a01d72f66db..2308c0a2fd29 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -1595,12 +1595,15 @@ static struct dyn_ftrace *lookup_rec(unsigned long = start, unsigned long end) unsigned long ftrace_location_range(unsigned long start, unsigned long end) { struct dyn_ftrace *rec; + unsigned long ip =3D 0; =20 + rcu_read_lock(); rec =3D lookup_rec(start, end); if (rec) - return rec->ip; + ip =3D rec->ip; + rcu_read_unlock(); =20 - return 0; + return ip; } =20 /** @@ -1614,25 +1617,22 @@ 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 /** @@ -6591,6 +6591,8 @@ 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; @@ -6804,6 +6806,9 @@ 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 */ @@ -7137,6 +7142,7 @@ 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; @@ -7178,12 +7184,8 @@ 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; @@ -7200,6 +7202,11 @@ 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 2.43.0