From nobody Mon Feb 9 00:56:24 2026 Received: from canpmsgout11.his.huawei.com (canpmsgout11.his.huawei.com [113.46.200.226]) (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 4767B23ABA9; Fri, 30 Jan 2026 03:53:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.226 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769745212; cv=none; b=c+1+lXokPGXD66GNPukfSzepwBF28ixJLnY13iUUdSgcmDsSh0l2npGDMGPZJ0lQSK9dklFEezSHjawwpyXLirpTZrSfgYWw57qPfI7VRcxs119g7O/dVDEUUSKZMjL/F60WIzH5ges1w8AvnhvBTy2qEic3kwKJR1QO4ptGK9U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769745212; c=relaxed/simple; bh=c/LM9EczxNfu+vU72bfyGHTGOcdwKx3f0bdQUZKOFM0=; h=From:To:CC:Subject:Date:Message-ID:MIME-Version:Content-Type; b=ItX9zjOQaSgHOwpHCz3kO/5o1IKoc4H6uCapCZO2ocYpMBgbBdl+dTkuuVKVELwTXHvcp3FE87ry49hwpF/eC9+Er51pWO+URsJTLTAMdwt3cjDB40fbUdouhUj7AbQc/VCiO1g8bQ91EQKsbVpQqyEGqKNxnq0ejjBUMV/9hDw= 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; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=mHCRPDth; arc=none smtp.client-ip=113.46.200.226 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 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="mHCRPDth" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=WzgdnpHVg8qATTW0+oSj7X+e+2LKXvcJ6CqfBSJBTOI=; b=mHCRPDthnqkpnD/vS05zi9ts7KcWBi8az4s6mwgOg8j8sG+bycJgJkS3Wq4e3FNdt45BC852k 28ARt1w2qA0iNjAem919E0o+jqmGiVL7xSQSvA+HM/AMATfdwiIVcHXdtOAPBfzxwSmkNAmm4ti WnwgiSkwDgS2ajaGJkO1rmY= Received: from mail.maildlp.com (unknown [172.19.163.127]) by canpmsgout11.his.huawei.com (SkyGuard) with ESMTPS id 4f2MTW3PjMzKmSj; Fri, 30 Jan 2026 11:49:51 +0800 (CST) Received: from kwepemk500005.china.huawei.com (unknown [7.202.194.90]) by mail.maildlp.com (Postfix) with ESMTPS id 315EB402AB; Fri, 30 Jan 2026 11:53:21 +0800 (CST) Received: from huawei.com (10.50.85.155) by kwepemk500005.china.huawei.com (7.202.194.90) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Fri, 30 Jan 2026 11:53:20 +0800 From: Zhihao Cheng To: , CC: , , , Subject: [PATCH] dcache: Limit the minimal number of bucket to two Date: Fri, 30 Jan 2026 11:48:53 +0800 Message-ID: <20260130034853.215819-1-chengzhihao1@huawei.com> X-Mailer: git-send-email 2.52.0 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: kwepems100002.china.huawei.com (7.221.188.206) To kwepemk500005.china.huawei.com (7.202.194.90) Content-Type: text/plain; charset="utf-8" There is an OOB read problem on dentry_hashtable when user sets 'dhash_entries=3D1': BUG: unable to handle page fault for address: ffff888b30b774b0 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page Oops: Oops: 0000 [#1] SMP PTI RIP: 0010:__d_lookup+0x56/0x120 Call Trace: d_lookup.cold+0x16/0x5d lookup_dcache+0x27/0xf0 lookup_one_qstr_excl+0x2a/0x180 start_dirop+0x55/0xa0 simple_start_creating+0x8d/0xa0 debugfs_start_creating+0x8c/0x180 debugfs_create_dir+0x1d/0x1c0 pinctrl_init+0x6d/0x140 do_one_initcall+0x6d/0x3d0 kernel_init_freeable+0x39f/0x460 kernel_init+0x2a/0x260 There will be only one bucket in dentry_hashtable when dhash_entries is set as one, and d_hash_shift is calculated as 32 by dcache_init(). Then, following process will access more than one buckets(which memory region is not allocated) in dentry_hashtable: d_lookup b =3D d_hash(hash) dentry_hashtable + ((u32)hashlen >> d_hash_shift) // The C standard defines the behavior of right shift amounts // exceeding the bit width of the operand as undefined. The // result of '(u32)hashlen >> d_hash_shift' becomes 'hashlen', // so 'b' will point to an unallocated memory region. hlist_bl_for_each_entry_rcu(b) hlist_bl_first_rcu(head) h->first // read OOB! Fix it by limiting the minimal number of dentry_hashtable bucket to two, so that 'd_hash_shift' won't exceeds the bit width of type u32. Cc: stable@vger.kernel.org Signed-off-by: Zhihao Cheng Reviewed-by: Yang Erkun --- fs/dcache.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index 66dd1bb830d1..957a44d2c44a 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -3260,7 +3260,7 @@ static void __init dcache_init_early(void) HASH_EARLY | HASH_ZERO, &d_hash_shift, NULL, - 0, + 2, 0); d_hash_shift =3D 32 - d_hash_shift; =20 @@ -3292,7 +3292,7 @@ static void __init dcache_init(void) HASH_ZERO, &d_hash_shift, NULL, - 0, + 2, 0); d_hash_shift =3D 32 - d_hash_shift; =20 --=20 2.52.0