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 988B335E92E for ; Fri, 27 Mar 2026 05:08:25 +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=1774588105; cv=none; b=uXY6A8n/ah6F+3VJrdUm9urFRL5nFDPElJqnKJdxVMRsTsso+stLsL1JiVwhSTVxSWr19NiCSJzkaNI7OLaOCHZSNSg6o2MxGecsZ/UICgSf9OQpEcfQUCeuNbHQkh6hskeyB7g40uoOPNaGxJy4IiMeTu8/iM9ijNkEDMGef+8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774588105; c=relaxed/simple; bh=jLVZdGJLJNiTat3VGSwLzz+NckJVPWrBPPP0mEtDVtk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=okX/7WE6Pb5kLcUzr4MZHp/ghXm4UGQwtJ1FvMEMBGBBNngtdXJK+IoniC8VG3kimbPBIYcsaDlhu8SVsKIf6TTJtPDYcH3nInjHGRVgSFxR3wBxBGdwQOuzMb+HUrazC26KW6BDKSi32W1dASZ01+1vNsQGmFbBK2+dRUgtHa0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ib2cxLuX; 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="ib2cxLuX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3256BC19423; Fri, 27 Mar 2026 05:08:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774588105; bh=jLVZdGJLJNiTat3VGSwLzz+NckJVPWrBPPP0mEtDVtk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ib2cxLuXrQb5riivetrfLXV+NLae0rUW28MkCQgXBjGZAN3Ny6KTDfiLSCQ+4DxD7 xH5XfAR6Mfcq1cMXeFUuBnqmRaHkqUo6xBwQ1tHRaj7sYnf7Uv0UsXyCWg1ry9Z5LQ /j10FjDAyzGUBwxauWd1pNAp/F978uroKinpw4khWxsTA3bgFTUVs069ekgs4ka+0t +jkIulvwALUR93wJSxRmx84ZFz3RJk3KyOXQJvgpbkRpIw4yBsrkre6wLx3DrBqoah JNwK+LFmWQgEaGo6dw5FUftiKyGGrltpDZFLHzjRuYYP22Z2wJRrCDshFS2FKI8rOq Lx+bheL4V2HuA== From: SeongJae Park To: Liew Rui Yan Cc: SeongJae Park , damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: (sashiko review) [RFC v5] mm/damon: add synchronous commit for commit_inputs Date: Thu, 26 Mar 2026 22:08:22 -0700 Message-ID: <20260327050823.43382-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260326061554.20466-1-aethernet65535@gmail.com> References: Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Thu, 26 Mar 2026 14:15:54 +0800 Liew Rui Yan wrote: > Hi SeongJae, > > On Wed, 25 Mar 2026 07:19:56 -0700, SeongJae Park wrote: > > > Hi Liew, > > > > On Wed, 25 Mar 2026 15:17:09 +0800 Liew Rui Yan wrote: [...] > > > I will add a patch in v6 to validate 'addr_unit' in addr_unit_store() to > > > reject non-power-of-2 inputs immediately. > > > > That's because kdamond_fn() has recently changed to exit the loop if > > damon_commit_ctx() fails in the loop for any reason. Refer to commit > > 26f775a054c3 ("mm/damon/core: avoid use of half-online-committed context") for > > more details. > > > > Adding the validation in addr_unit_store() would work, but it could be a kind > > of whack-a-mole game. I'd prefer doing the validation of all inputs in one > > place, just before the last damon_commit_ctx() call. DAMON_SYSFS is doing so, > > by making a test context and try committing user input to the test context > > before doing that to the running context. How about doing so here, too? > > Thank you for the suggestion. I have now added the check > '!src->addr_unit || ! is_power_of_2(src->addr_unit)' to > damon_commit_ctx(). No, what I'm suggesting is not adding more checks, but reusing the existing checks in damon_commit_ctx(). And, now I think bit differently. Given the purpose of this patch is making commit_inputs synchronous, I think making more complete validation check is somewhat that can be done separately. So my suggestion now is just keeping this part just as is. [...] > > So the issue already exists. But let's ensure the fix is merged before this > > patch, since this patch adds another exploitable path that can consequence in > > whole param_lock deadlock. > > Should I wait for your fix to be merged into damon/next before I post > the next version? As long as you agree about the mainline merge order, I think you don't need to wait for my fix. Please feel free to post next version. FYI, the latest version of my fix is available [1] on the mailing list. [1] https://lore.kernel.org/20260327004952.58266-1-sj@kernel.org Thanks, SJ [...]