From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 7895841A503 for ; Mon, 24 Aug 2026 12:02:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787572972; cv=none; b=N1dLB28MRXeoD3EjRf5gsCiCuULMP3xBAqRZ2O7X2v6exIyuNX0+SJrhY69ISTjdyqwhl4Ml0fB8aoI4MoZfDYZh/YDaqNBK1bX6gwq41wjJHKA5kBHFlrNvvS47psnQ+hcCTfI3W9Cgk3i68dlgh/DA6q5BRC7kdxt3EiivvAc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787572972; c=relaxed/simple; bh=QrVxkC1qUai+LkpCyw0Tz6tntuP4Wpe1tMlKeqdSWwU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fOL7b6InCjk1nm5LGgVBKJKXJpQHXLzlALg5PlcEJo72PX9QFzE8CHJ3nKdvBU1KgGM4ZsgTU0cIAx6BgizGNRFDBVBv+WuHhA0K6Rr8CQ2hkoBDgdP4T5ULSYlCMd+0f5R05FVN9qe5im7ZX54YOsDy2+wL6Z2/CWWCBxgvkZE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=S27GhQoi; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="S27GhQoi" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1787572969; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hoJL241RSoxtycntHxJVxwYZyJBhwGJRmdZEHBFJJr0=; b=S27GhQoi57XgQYJ3kkJDI7q9TqHkBhc9zRUvUwXoAfekt4z5YSwy6UPJxeERF/F8X/Kk3k b448Hii9lWY1NA2yUvZA1FiyyubjnNzFdViy8DJRKYCKxLnXBJp3Xj83yFc+PyCRrIdeOt ehlMl4poGJj3s5Lnysk0jxqNC30OwDE= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-634-PXsIUWAfMBqM0Rgk4A1ljw-1; Mon, 24 Aug 2026 08:02:46 -0400 X-MC-Unique: PXsIUWAfMBqM0Rgk4A1ljw-1 X-Mimecast-MFC-AGG-ID: PXsIUWAfMBqM0Rgk4A1ljw_1787572965 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 1665C1977038; Mon, 24 Aug 2026 12:02:45 +0000 (UTC) Received: from warthog.com (unknown [10.44.32.15]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 3D7851955F07; Mon, 24 Aug 2026 12:02:42 +0000 (UTC) From: David Howells To: Christian Brauner Cc: David Howells , Paulo Alcantara , netfs@lists.linux.dev, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 3/3] cachefiles: Fix potential UAF/KASAN warning Date: Mon, 24 Aug 2026 13:02:22 +0100 Message-ID: <20260824120224.504575-4-dhowells@redhat.com> In-Reply-To: <20260824120224.504575-1-dhowells@redhat.com> References: <20260824120224.504575-1-dhowells@redhat.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 Currently, trace_cachefiles_coherency() is being passed a pointer to a __be64 lain over the coherency data in struct cachefiles_xattr so that it can display the first 8 bytes. However, the data is of variable length and could even be 0 bytes. This could lead to a UAF or KASAN warning. Fix this by making sure the buffer has room for at least 8 bytes and that those 8 bytes are pre-cleared. Further, those bytes are not 8-byte aligned, so fix the tracepoint to extract the data as four 2-byte words (they are 2-byte aligned) and reassemble the __be64. The compiler will convert this into a single 8-byte load where the CPU supports it. Fixes: 229105e5cfd9 ("cachefiles: Add auxiliary data trace") Link: https://sashiko.dev/#/patchset/20260810144746.574036-1-dhowells%40redhat.com Signed-off-by: David Howells cc: Paulo Alcantara cc: netfs@lists.linux.dev cc: linux-fsdevel@vger.kernel.org --- fs/cachefiles/xattr.c | 16 ++++++++-------- include/trace/events/cachefiles.h | 19 +++++++++++++++++-- 2 files changed, 25 insertions(+), 10 deletions(-) diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c index f8ae78b3f7b6..92990cfdcca7 100644 --- a/fs/cachefiles/xattr.c +++ b/fs/cachefiles/xattr.c @@ -13,6 +13,7 @@ #include #include #include +#include #include "internal.h" #define CACHEFILES_COOKIE_TYPE_DATA 1 @@ -50,7 +51,7 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object) _enter("%x,#%d", object->debug_id, len); - buf = kmalloc(sizeof(struct cachefiles_xattr) + len, GFP_KERNEL); + buf = kmalloc(sizeof(struct cachefiles_xattr) + min(len, sizeof(__be64)), GFP_KERNEL); if (!buf) return -ENOMEM; @@ -60,6 +61,7 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object) buf->content = object->content_info; if (test_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags)) buf->content = CACHEFILES_CONTENT_DIRTY; + put_unaligned_be64(0, (__be64 *)buf->data); if (len > 0) memcpy(buf->data, fscache_get_aux(object->cookie), len); @@ -77,8 +79,7 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object) trace_cachefiles_vfs_error(object, file_inode(file), ret, cachefiles_trace_setxattr_error); trace_cachefiles_coherency(object, file_inode(file)->i_ino, - be64_to_cpup((__be64 *)buf->data), - buf->content, + buf->data, buf->content, cachefiles_coherency_set_fail); if (ret != -ENOMEM) cachefiles_io_error_obj( @@ -86,8 +87,7 @@ int cachefiles_set_object_xattr(struct cachefiles_object *object) "Failed to set xattr with error %d", ret); } else { trace_cachefiles_coherency(object, file_inode(file)->i_ino, - be64_to_cpup((__be64 *)buf->data), - buf->content, + buf->data, buf->content, cachefiles_coherency_set_ok); } @@ -110,9 +110,10 @@ int cachefiles_check_auxdata(struct cachefiles_object *object, struct file *file int ret = -ESTALE; tlen = sizeof(struct cachefiles_xattr) + len; - buf = kmalloc(tlen, GFP_KERNEL); + buf = kmalloc(sizeof(struct cachefiles_xattr) + min(len, sizeof(__be64)), GFP_KERNEL); if (!buf) return -ENOMEM; + put_unaligned_be64(0, (__be64 *)buf->data); xlen = cachefiles_inject_read_error(); if (xlen == 0) @@ -148,8 +149,7 @@ int cachefiles_check_auxdata(struct cachefiles_object *object, struct file *file out: trace_cachefiles_coherency(object, file_inode(file)->i_ino, - be64_to_cpup((__be64 *)buf->data), - buf->content, why); + buf->data, buf->content, why); kfree(buf); return ret; } diff --git a/include/trace/events/cachefiles.h b/include/trace/events/cachefiles.h index 9259bc71049e..927338f8fe85 100644 --- a/include/trace/events/cachefiles.h +++ b/include/trace/events/cachefiles.h @@ -372,7 +372,7 @@ TRACE_EVENT(cachefiles_rename, TRACE_EVENT(cachefiles_coherency, TP_PROTO(struct cachefiles_object *obj, ino_t ino, - u64 disk_aux, + const void *disk_aux, enum cachefiles_content content, enum cachefiles_coherency_trace why), @@ -389,12 +389,27 @@ TRACE_EVENT(cachefiles_coherency, ), TP_fast_assign( + union { + __be16 s[4]; + __be64 ll; + } x; + __entry->obj = obj->debug_id; __entry->why = why; __entry->content = content; __entry->ino = ino; __entry->aux = be64_to_cpup((__be64 *)obj->cookie->inline_aux); - __entry->disk_aux = disk_aux; + + /* cachefiles_xattr::data is not 64-byte aligned. */ + if (disk_aux) { + x.s[0] = ((__be16 *)disk_aux)[0]; + x.s[1] = ((__be16 *)disk_aux)[1]; + x.s[2] = ((__be16 *)disk_aux)[2]; + x.s[3] = ((__be16 *)disk_aux)[3]; + __entry->disk_aux = be64_to_cpu(x.ll); + } else { + __entry->disk_aux = 0; + } ), TP_printk("o=%08x %s B=%llx c=%u aux=%llx dsk=%llx",