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 C8889265CAB for ; Tue, 16 Sep 2025 07:28:34 +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=1758007714; cv=none; b=Lmp+mQxNnn4HJWYItX95bLl/dUAT70oyFc8GFtJXcKX58ViydtvDvinh6gJ3jceAjSVa7Xot98psVikNdaJ5cXdThoTwraEsFu6qQ1RJnPK/gmvU1UgC2Gb5SYAcJKCLudi73npI3/uuIdHPlN5sm0roy6P+4pN3mWOV5IxyYJc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758007714; c=relaxed/simple; bh=DYAXQCcr75Fy8fYpNafpW9dWhyLeE+JscgT1dXk3NdM=; h=Message-ID:Date:MIME-Version:Cc:Subject:To:References:From: In-Reply-To:Content-Type; b=fr2pjoLOGoFvlqwVL5qZ3egnfIm1JyIAg4Ae7tbke28Qxlc8pnHTPl5ZZ+U861nG4njW+UvUZZPnvxA53mQ2j7BShy1bCY0DFFLB57Ijut2aiSYwDLALU4J2QsWvm1XqnJxbsWw2HncPx4ggujSt7HPx/jQlhDlDBKgySnOMhOY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RCwihVVo; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="RCwihVVo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D972FC4CEEB; Tue, 16 Sep 2025 07:28:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1758007714; bh=DYAXQCcr75Fy8fYpNafpW9dWhyLeE+JscgT1dXk3NdM=; h=Date:Cc:Subject:To:References:From:In-Reply-To:From; b=RCwihVVoCEMEZy0QGLPEtqnRHMl82oj9JD8ScaARQCN0K9DldLxgZA8aBies5hi+d UxPaq7mnGqY7VeTOhp/vVLvY6x4nr79Ci3X/WXjDS1W/FotCWusHE27z/hIa0nv/LP 2n2Kxh8Le6D8wYrJPKf5QpjhZn3AYjJgvDuVaF3Fj0WR+h7wIlPK1GqP19pygXIqI2 gbIlELwW4kNxAW0Bhl28z8XWiJTpFOtcotgUpKGz9grO8M6aq1zc7EwOITUm1DZPqB +MS9+/GjR3dtUfWjXRA6qyIXipHdDUZ0DHOM67CgliII5V8HIioPkJHWC3SsYAVaOz qYuxMoRn+EdqA== Message-ID: <62d7f4d3-cc9c-429f-8b7e-0e80e2aa24e4@kernel.org> Date: Tue, 16 Sep 2025 15:28:30 +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 Cc: chao@kernel.org, bintian.wang@honor.com, feng.han@honor.com, jaegeuk@kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [f2fs-dev] [PATCH v2 2/2] f2fs: fix infinite loop in __insert_extent_tree() To: wangzijie References: <20250916070946.231825-1-wangzijie1@honor.com> Content-Language: en-US From: Chao Yu In-Reply-To: <20250916070946.231825-1-wangzijie1@honor.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 9/16/25 15:09, wangzijie wrote: >> On 9/16/25 13:22, wangzijie wrote: >>>> On 09/15, wangzijie wrote: >>>>> When we get wrong extent info data, and look up extent_node in rb tree, >>>>> it will cause infinite loop (CONFIG_F2FS_CHECK_FS=n). Avoiding this by >>>>> return NULL. >>>> >>>> This is the exact buggy case which we should fix the original one. Have >>>> you seen this error? In that case, can we consider writing some kernel >>>> message and handle the error properly? >>> >>> Hi Jaegeuk, >>> The original one is the bug I mentioned in the first patch of this patch set >>> ("f2fs: fix zero-sized extent for precache extents"). >> >> Zijie, >> >> Did you suffer this problem in product? right? > > Hi Chao, > Yes, and I can confirm that infinite loop cases I suffered are caused by the bug I > mentioned in the first patch of this patch set. But I'm not sure if there are > other cases that can cause this infinite loop. > >>> >>> When we use a wrong extent_info(zero-sized) to do update, and there exists a >>> extent_node which has same fofs as the wrong one, we will skip "invalidate all extent >>> nodes in range [fofs, fofs + len - 1]"(en->ei.fofs = end = tei->fofs + tei->len = tei->fofs), >>> which cause the infinite loop in __insert_extent_tree(). >>> >>> So we can add f2fs_bug_on() when there occurs zero-sized extent >>> in f2fs_update_read_extent_cache_range(), and give up this zero-sized >>> extent update to handle other unknown buggy cases. Do you think this will be better? >>> >>> And do we need to solve this infinite loop? >> >> IMO, it's worth to end such loop if there is any corrupted extent in rbtree to >> avoid kernel hang, no matter it is caused by software bug or hardware flaw >> potentially. >> >> Thanks, > > And do you think we need this? > "add f2fs_bug_on() when there occurs zero-sized extent in f2fs_update_read_extent_cache_range(), > and give up this zero-sized extent update to handle other unknown buggy cases". Oh, I was testing below patch..., does this what you want to do? I think we can keep all your patches, and appending below patch to detect any potential cases who will update a zero-sized extent. >From 439d61ef3715fafa5c9f2d1b7f8026cdd2564ca7 Mon Sep 17 00:00:00 2001 From: Chao Yu Date: Tue, 16 Sep 2025 11:52:30 +0800 Subject: [PATCH] f2fs: add sanity check on ei.len in __update_extent_tree_range() Add a sanity check in __update_extent_tree_range() to detect any zero-sized extent update. Signed-off-by: Chao Yu --- fs/f2fs/extent_cache.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c index 199c1e7a83ef..9544323767be 100644 --- a/fs/f2fs/extent_cache.c +++ b/fs/f2fs/extent_cache.c @@ -664,6 +664,15 @@ static void __update_extent_tree_range(struct inode *inode, if (!et) return; + if (unlikely(len == 0)) { + f2fs_bug_on(sbi, 1); + f2fs_err_ratelimited(sbi, "%s: extent len is zero, type: %d, " + "extent [%u, %u, %u], age [%llu, %llu]", + __func__, type, tei->fofs, tei->blk, tei->len, + tei->age, tei->last_blocks); + return; + } + if (type == EX_READ) trace_f2fs_update_read_extent_tree_range(inode, fofs, len, tei->blk, 0); -- 2.49.0 > > > >>> >>> >>>>> >>>>> Signed-off-by: wangzijie >>>>> --- >>>>> fs/f2fs/extent_cache.c | 1 + >>>>> 1 file changed, 1 insertion(+) >>>>> >>>>> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c >>>>> index 199c1e7a8..6ed6f3d1d 100644 >>>>> --- a/fs/f2fs/extent_cache.c >>>>> +++ b/fs/f2fs/extent_cache.c >>>>> @@ -605,6 +605,7 @@ static struct extent_node *__insert_extent_tree(struct f2fs_sb_info *sbi, >>>>> leftmost = false; >>>>> } else { >>>>> f2fs_bug_on(sbi, 1); >>>>> + return NULL; >>>>> } >>>>> } >>>>> >>>>> -- >>>>> 2.25.1 >