From mboxrd@z Thu Jan 1 00:00:00 1970 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 BEB74335BA7; Mon, 20 Apr 2026 16:12:24 +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=1776701544; cv=none; b=mZ46QL8lDLVNVDLa5b4IxsouQWFFSiSsDVwdolQTr8zAy9FmjLoS9iwGhrNJoOVeG1M5MFfthz6hzicx7GiY6GpsRdaXRZI1rMWwdrltp9b8v6jHUh3QZmRBoIGRnLc+6TeX1N4x3ljXGNg91u8CfEW7IObID6QaeYcMEEhmmrs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776701544; c=relaxed/simple; bh=LIGHbh45xoKeLgBIY23DxuhSmXmjO6BYVDoU+1KnJl4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=I3bKd9nmCS9to8HuyzHg5/oAVciPudNHelTIHyCMCplkebHLnksCL7mpyBnhLOe0hITVVo+y6mR1vLoRoif6SZm19FqDVhIlKjaysZp7UoMxdNOcnUpUpgRdpTjE9yMSCJgZb9fVG6d74c5nBZkjrgGHTVaFp/zQkcD/5zkID3M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BTGdVSxR; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="BTGdVSxR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 549D6C19425; Mon, 20 Apr 2026 16:12:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1776701544; bh=LIGHbh45xoKeLgBIY23DxuhSmXmjO6BYVDoU+1KnJl4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BTGdVSxRNyRHyT7p5iE0ZdpTH6Lq+Vy+isfklzw4tlAcnzWjeBsTqcMp8VOH8mBcm z6u8fCyl4cEfva8dLlzIMiJb590q9+O81PPHH9ndu5CPsUzJILVI+dV7vllfv1Nc01 EWkTEbUM+Xj8amdBxlDBj1yl6eMHJ4BxcmydphhE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zhihao Cheng , Yang Erkun , Christian Brauner Subject: [PATCH 6.12 123/162] dcache: Limit the minimal number of bucket to two Date: Mon, 20 Apr 2026 17:42:35 +0200 Message-ID: <20260420153931.497160702@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260420153927.006696811@linuxfoundation.org> References: <20260420153927.006696811@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zhihao Cheng commit f08fe8891c3eeb63b73f9f1f6d97aa629c821579 upstream. There is an OOB read problem on dentry_hashtable when user sets 'dhash_entries=1': 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 = 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 Link: https://patch.msgid.link/20260130034853.215819-1-chengzhihao1@huawei.com Reviewed-by: Yang Erkun Signed-off-by: Christian Brauner Signed-off-by: Greg Kroah-Hartman --- fs/dcache.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/fs/dcache.c +++ b/fs/dcache.c @@ -3127,7 +3127,7 @@ static void __init dcache_init_early(voi HASH_EARLY | HASH_ZERO, &d_hash_shift, NULL, - 0, + 2, 0); d_hash_shift = 32 - d_hash_shift; @@ -3158,7 +3158,7 @@ static void __init dcache_init(void) HASH_ZERO, &d_hash_shift, NULL, - 0, + 2, 0); d_hash_shift = 32 - d_hash_shift;