From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) (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 D716A328610 for ; Mon, 5 Jan 2026 08:54:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767603285; cv=none; b=E7Jl5GB/hB1ZsjU0XFZAWj6kg3xh+MyVIzjGouFLr8gbkFmX/PkOWU+zMXJStwmxZGaqe7fvEQ1Bcbvs1WHYTfiihxQC9/d5nfcSVzapatYc/LDsdeSP/I2Y5dTskCGucXYylmIFditw7+1xxmYSSTh5MKsMP5wa5+iZnHvv4zY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767603285; c=relaxed/simple; bh=qs5Cc881E6Yw59DrLYnc58Rgo6i4XnVF8LHbLKZDBOk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kOsObzcmbmCfBFWj/oxSE4lWTOw78pQp+eCQSFCx/SRO5urBC7LIwyYijvXn7HXadK9WawOp9L2Z7eWlALW+R7FR8iv7PKEKOrMIS5iiirLOleSROJMdSMZpym5ouHiCrBm4L6yX6ZvGUiOFtYz0S0rq1siKIpYa/pyFxEG/o1Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=hMyeT8J/; arc=none smtp.client-ip=115.124.30.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="hMyeT8J/" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1767603272; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=r55kyqmmD/uClVKO277vu4AQCwQE5+8myu34W1wd2+s=; b=hMyeT8J/uXUvizAWj8ZqDevc/mvjiP1qDPjmbD8bpemy5Q36JDUL8fza4+FTsD6hjw1fC+sQXlof7+QqcW6iSPCoEv62vTNn/CAOT7Bim5mqixzRlsWF+FOCedlJ9azMDJk04WNdR0Zci84/8LJAlhvMrbBTjspqrAXioru61YM= Received: from 30.74.144.119(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WwM6l9s_1767603271 cluster:ay36) by smtp.aliyun-inc.com; Mon, 05 Jan 2026 16:54:31 +0800 Message-ID: <5fd5013d-89b7-4d32-b655-67bd9d103f04@linux.alibaba.com> Date: Mon, 5 Jan 2026 16:54:30 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/shmem: fix uninitialized folio in shmem_symlink To: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Barry Song , Hugh Dickins , syzbot+178fff6149127421c2cc@syzkaller.appspotmail.com References: <20251224094027.65842-1-21cnbao@gmail.com> From: Baolin Wang In-Reply-To: <20251224094027.65842-1-21cnbao@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12/24/25 5:40 PM, Barry Song wrote: > From: Barry Song > > Uninitialized folio allocated in shmem_symlink() may be accessed > during swap-out, causing KMSAN BUG: > > BUG: KMSAN: uninit-value in is_folio_zero_filled mm/page_io.c:188 [inline] > BUG: KMSAN: uninit-value in swap_writeout+0x468/0x1390 mm/page_io.c:263 > is_folio_zero_filled mm/page_io.c:188 [inline] > swap_writeout+0x468/0x1390 mm/page_io.c:263 > shmem_writeout+0x1abb/0x1f60 mm/shmem.c:1662 > writeout mm/vmscan.c:649 [inline] > pageout mm/vmscan.c:698 [inline] > shrink_folio_list+0x5920/0x7fc0 mm/vmscan.c:1418 > evict_folios+0x999d/0xbf30 mm/vmscan.c:4711 > try_to_shrink_lruvec+0x12b6/0x17e0 mm/vmscan.c:4874 > lru_gen_shrink_lruvec mm/vmscan.c:5023 [inline] > shrink_lruvec+0x46f/0x4f10 mm/vmscan.c:5784 > shrink_node_memcgs mm/vmscan.c:6020 [inline] > > This patch clears the remaining part to zero for the portion not > covered by memcpy from symname. > > Cc: Hugh Dickins > Cc: Baolin Wang > Reported-by: syzbot+178fff6149127421c2cc@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/lkml/6949370f.050a0220.1b4e0c.0038.GAE@google.com/ > Signed-off-by: Barry Song > --- LGTM. Thanks. Reviewed-by: Baolin Wang > mm/shmem.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/shmem.c b/mm/shmem.c > index ec6c01378e9d..835900a08f51 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -4131,6 +4131,7 @@ static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir, > goto out_remove_offset; > inode->i_op = &shmem_symlink_inode_operations; > memcpy(folio_address(folio), symname, len); > + folio_zero_range(folio, len, folio_size(folio) - len); > folio_mark_uptodate(folio); > folio_mark_dirty(folio); > folio_unlock(folio);