From nobody Tue Sep 29 01:17:41 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 EAF36381B0C; Thu, 13 Aug 2026 21:19:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786655964; cv=none; b=tI9qMvlU0o1MngHFl5iYTn6ZP0Z1dKUim5liDMBBtCMKS2D58wMW8sm2fbb1f+YiBPv6dwj+lsdO5yvDlIHJ53owUjAQ4RbHrd68WqY0XOOIElz24gFYVirJSOFjqiQdFmYclbyKiE5qSUA9EdIPDV7+XDoqFsopufcoF7dCGxo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786655964; c=relaxed/simple; bh=drEiQ4Vb5t7drAwrcxOPtTvK5P+J6gBeRJxjCxi1YiQ=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=uvMtMhlh5ow5G6Lb5cY1Y/RTJLvR2A+XntlBH7/gib03vmC2Db05wO2aJXQuHbP88l6S8V2+v772M10VJmbh8i/5YdgLPROwo0/0GkKqLQ8zDcvKwbgriDIK1UDgQqjA4tch4DkYkTwq+fgtIp9Ng5u08ymC7+6F4iCgSCvp9Pk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=j3cOtecP; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="j3cOtecP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C20C21F00A3A; Thu, 13 Aug 2026 21:19:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786655949; bh=7TySX38qpXOkdseJZaIINs0UNHO118jzm0H0b714RJc=; h=Date:From:To:Cc:Subject:References; b=j3cOtecPiz10ZbLibZYci1buEOAcZ3YbgPR7B9lz9otO+lePyM0CFV9tXgY/CAmnU JTc55cm96sJxgJoWQM6xNUx4DtWwPyldeJ49vGWtMh/IWfJkutosZ+++3G09UWYpch SJns66SrHblRNUUkRIuTrwP1ldB8/fVy6FPz/Lj9OaCXVvBbYDCKDZj4Q3BbkkLUAW CLKwImccGrcgReuGiLbIzxggtd76EbCjbW67m7GvHVVYPa/sGh5u78yxxZKcioz4cj zos2N9byDgmYjMq2ImQFuWm4Nx0b5FnBgQny9fHx5inIDBhNZzEir43bEERKVdNnep X6xNZxYL9pKCw== Received: from rostedt by gandalf with local (Exim 4.99.4) (envelope-from ) id 1wucpi-00000003k8s-3AB6; Thu, 13 Aug 2026 17:19:26 -0400 Message-ID: <20260813211926.612218140@kernel.org> User-Agent: quilt/0.69 Date: Thu, 13 Aug 2026 17:19:14 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , stable@vger.kernel.org, syzbot+4d3143c8e28f6266c636@syzkaller.appspotmail.com, Hui Su Subject: [for-linus][PATCH 1/2] tracing: Fix NULL pointer dereference in module event cache removal References: <20260813211913.824371874@kernel.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: Hui Su A module-only event filter such as ":mod:foo" is cached with a NULL event_mod->match when foo has not been loaded. If a later write tries to remove a specific match from the same module, remove_cache_mod() passes the NULL cached match to strcmp(), causing a NULL pointer dereference. The issue can be reproduced from userspace: echo ':mod:trace_events_kunit_missing' > /sys/kernel/tracing/set_event echo '!foo_bar:mod:trace_events_kunit_missing' >> /sys/kernel/tracing/set= _event The second write must be a concatenation (">>") to not include O_TRUNC as that would cause ftrace_clear_events() to clear the cached modules lines. The crash was reproduced on x86_64 QEMU while KUnit workers contended on the event tracing path: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode RIP: 0010:strcmp+0x10/0x30 Call Trace: __ftrace_set_clr_event_nolock+0x373/0x4a0 ftrace_set_clr_event+0xf0/0x180 ftrace_event_write+0xdf/0x110 vfs_write+0xf6/0x440 ksys_write+0x68/0xe0 do_syscall_64+0xf9/0x540 entry_SYSCALL_64_after_hwframe+0x77/0x7f Check event_mod->match before comparing it, consistent with the existing NULL checks for the cached system and event fields. The mismatched removal continues to return -EINVAL; a broad cached module filter is removed with "!:mod:". Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260811173902.1927376-2-sh_def@163.com Fixes: b355247df104 ("tracing: Cache \":mod:\" events for modules not loade= d yet") Reported-by: syzbot+4d3143c8e28f6266c636@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/6a7a6b7f.9c11d2ce.289b96.00f8.GAE@goog= le.com/ Signed-off-by: Hui Su Signed-off-by: Steven Rostedt --- kernel/trace/trace_events.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index c01b10b99f67..032f741ba616 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -945,7 +945,7 @@ static int remove_cache_mod(struct trace_array *tr, con= st char *mod, if (strcmp(event_mod->module, mod) !=3D 0) continue; =20 - if (match && strcmp(event_mod->match, match) !=3D 0) + if (match && (!event_mod->match || strcmp(event_mod->match, match) !=3D = 0)) continue; =20 if (system && --=20 2.53.0 From nobody Tue Sep 29 01:17:41 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 EC90E43E4BB; Thu, 13 Aug 2026 21:19:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786655961; cv=none; b=slET7JDutdwAy8dJzAR9B797RJeBdCsvppU6j9BRGPuZ7/VJiEQS7qc/O8RfZemxng1qXl5VhSqli8FKWAmtqYBkrMfaDS4/lLrHtME5kNGt+D3YWnv+cr2SarowKl3GeSqm2uFKYWUF+ozUqqDu9xP88+RLmOdzqEXbQbYimps= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786655961; c=relaxed/simple; bh=3cUJ2kbgAda/3KuyQsg5scFPZj1YIUFT4vrVWZpCcBc=; h=Message-ID:Date:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=B+PqBv6BdaHZhxTrcWtOCsL/8Jh9sLrZs44x7O/NmTswMJjwH9qeBXxqfAlA0WX7LWAhl7FZg3Ks11HuGvQ3IA4C91PAWJOhlCQojPBj+zgyAcCEaiWMmYMLXkUFF3mVjPavRgyKtSBJj0uBk/oh4hhM0fhveBzr/Ep/xR18zas= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AYYdJvwK; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AYYdJvwK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DF43E1F00A3E; Thu, 13 Aug 2026 21:19:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786655949; bh=i+tiIW9fCiXODs9ZRk07BdX+/ESQJtYU52s3f4oUmVY=; h=Date:From:To:Cc:Subject:References; b=AYYdJvwK3fiTKhE/9OKdtyhpH0duaZiEZs7oF/Dr/74KUWgGzksHl3y3XMfeVI8ob ko0ng9aIdJW25hxV0eJeBD1VXr5QNz+TFAvevBtCJdRzbUZsytSrC1u8UYCFajCWS6 7BumFrnkH7O0NtnoqNwgombPVrfx3v08TwFuHlyMul6Qi5uonOBopJu70Uk9k0ZhnS 0K1mpVYdQEYt5H36OTN/tIHNAxZbnaAijt0fhu5TJd/jLU0DXybbhdP48hECE87duv vQQgrXtEykIf6Z30DlhYnl/KuQFfnxMBQGC/nU5lwfIZOP2K9Cn1TwxsHlNLuQvUKF 0wXW+FqujSJCQ== Received: from rostedt by gandalf with local (Exim 4.99.4) (envelope-from ) id 1wucpi-00000003k9M-3quG; Thu, 13 Aug 2026 17:19:26 -0400 Message-ID: <20260813211926.773252765@kernel.org> User-Agent: quilt/0.69 Date: Thu, 13 Aug 2026 17:19:15 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , stable@vger.kernel.org, Michael Wu Subject: [for-linus][PATCH 2/2] tracing: Fix race between update_event_fields and, event_define_fields References: <20260813211913.824371874@kernel.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: Michael Wu The following sequence may leads race between event_define_fields() and update_event_fields(): CPU0 (loads module A) CPU1 (loads module B) =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D load_module(A) load_module(B) notifier_call_chain notifier_call_chain trace_module_notify trace_module_notify mutex_lock(&event_mutex) trace_event_update_all() trace_module_add_events(A) down_write(&trace_event= _sem) __register_event(call_A) __add_event_to_tracers(call_A) event_define_fields(call_A) for each f: list_for_each_entry(f= ield, list_add(&f->link, &= class->fields, link) &class->fields) field =3D class->fi= elds->next; Where access to the class->fields is not protected by the event_mutex in trace_event_update_all(). This produces the following panic: Unable to handle kernel access ... at virtual address 0000000000000018 pc : update_event_fields+0xf8/0x368 Call trace: update_event_fields+0xf8/0x368 trace_event_update_all+0x7c/0x2b4 trace_module_notify+0x4c/0x1dc notifier_call_chain+0x84/0x168 blocking_notifier_call_chain_robust+0x64/0xd4 load_module+0x10c8/0x123c __arm64_sys_finit_module+0x230/0x31c Fix by taking event_mutex in trace_event_update_all() before trace_event_sem. Cc: stable@vger.kernel.org Fixes: b3bc8547d3be ("tracing: Have TRACE_DEFINE_ENUM affect trace event ty= pes as well") Link: https://patch.msgid.link/2e5730d2-c631-da41-3a3a-ae35bb4895f3@allwinn= ertech.com Signed-off-by: Michael Wu Signed-off-by: Steven Rostedt --- kernel/trace/trace_events.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 032f741ba616..3650d84d4f16 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -3566,6 +3566,7 @@ void trace_event_update_all(struct trace_eval_map **m= ap, int len) int last_i; int i; =20 + mutex_lock(&event_mutex); down_write(&trace_event_sem); list_for_each_entry_safe(call, p, &ftrace_events, list) { /* events are usually grouped together with systems */ @@ -3604,6 +3605,7 @@ void trace_event_update_all(struct trace_eval_map **m= ap, int len) cond_resched(); } up_write(&trace_event_sem); + mutex_unlock(&event_mutex); } =20 static bool event_in_systems(struct trace_event_call *call, --=20 2.53.0