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 D7CBC2DE70B; Thu, 26 Feb 2026 20:35:15 +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=1772138115; cv=none; b=ElRN0b8dapA8kKVkzDLQbr5282ZWwMIw4uzPenrFqbww1wDWTP8pvbzb5QuiCoPzNdiCWdqenK/qoR6FhPYDXZetY0eHe/u3xyWPsk9mrBixInbNsxU0HD6p29S8XftWnPJ92udVInWjQpm0xhVT1MwCe9NN2zu5NeOak59bYUc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772138115; c=relaxed/simple; bh=ttfDVW7C9pCIAoD1kF2vqxPvmPicC5zaoO2riwOvrNg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=cJRAuepnO6DFwiXXuvidOqfaWAyf/VjOjXDYEEQGGKYxI5Pav7Cdur0CEmWK2pDYk1KJvIX3IxPKrELKf4zpT7NTbhA7o5UQLD21pFPIqZ+8Wq2AfffUVcoXjrHc1VeqaTTjRx6jw7W59lwET737Thb2FMGOEqFeUl5O9aPhZxI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Efs813WP; 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="Efs813WP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2F95FC116C6; Thu, 26 Feb 2026 20:35:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772138115; bh=ttfDVW7C9pCIAoD1kF2vqxPvmPicC5zaoO2riwOvrNg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Efs813WPjrcZZR3B89J9fe4/UEZuGmTqUNfILzdAUsK38oEDyhuMBzm6US7lNymqK jGo8tuQREBQY+2PB+BWnjwUoxHOrabxzqtARaZaeOV9boQjkgqG5iYf50CcbN9B0A+ RLTVA+Gz5+83R3Cyp4VvZ5Zhq1eMQMiqzAWodCH4ht4QUrvlss2fdROVKnhHIS888k P6Ds31RywUD2LWPvBb14z0vKIxjaejpz72AQqR8EESk+FNSqIJUAMvQIgvndqqD5qO l2u4fzVrE0jn/xT6/eR2KESK6CvD2EiKJamNcMbxme8KzG4Cv2mKp2MpMzqE6ZoWG7 a3lJ2zQjzGClg== Date: Thu, 26 Feb 2026 13:35:11 -0700 From: Nathan Chancellor To: Xingjing Deng Cc: nsc@kernel.org, rdunlap@infradead.org, masahiroy@kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] kconfig: fix potential NULL pointer dereference in conf_askvalue Message-ID: <20260226203511.GB3196155@ax162> References: <20260225072246.3475275-1-micro6947@gmail.com> <20260225194404.GD2755225@ax162> Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Thu, Feb 26, 2026 at 09:25:28AM +0800, Xingjing Deng wrote: > Nathan Chancellor 于2026年2月26日周四 03:44写道： > > > > On Wed, Feb 25, 2026 at 07:22:46AM +0000, Xingjing Deng wrote: > > > In conf_askvalue(), the 'def' argument (retrieved via sym_get_string_value) > > > can be NULL. When the symbol is not changeable, the code calls > > > printf("%s\n", def), which leads to a segmentation fault on certain > > > systems/libc implementations when passing a NULL pointer to %s. > > > > How do you reproduce this segmentation fault? Surely someone would have > > hit this if it were a real problem given the Fixes tag? Or is this a > > corner case? > > I tested printing NULL with printf locally and confirmed that it does > cause issues. In my opinion, this problem is more of a corner case—I > identified it through static program analysis and have not yet > reproduced it in practice. Thanks for confirming. I think it would be better to make this clearer in the commit message because it reads as though the problem is reproducible in practice. Also, 'def ?: ""' would do the same thing with fewer characters. Cheers, Nathan