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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id f10-20020a170902860a00b0015e8d4eb1fcsm1871783plo.70.2022.05.05.11.39.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 May 2022 11:39:18 -0700 (PDT) Date: Thu, 5 May 2022 11:39:17 -0700 From: Kees Cook To: Paul Moore Cc: "Gustavo A. R. Silva" , Steffen Klassert , Herbert Xu , "David S. Miller" , Stephen Smalley , Eric Paris , Nick Desaulniers , Xiu Jianfeng , Christian =?iso-8859-1?Q?G=F6ttsche?= , netdev@vger.kernel.org, selinux@vger.kernel.org, Alexei Starovoitov , alsa-devel@alsa-project.org, Al Viro , Andrew Gabbasov , Andrew Morton , Andy Gross , Andy Lavr , Arend van Spriel , Baowen Zheng , Bjorn Andersson , Boris Ostrovsky , Bradley Grove , brcm80211-dev-list.pdl@broadcom.com, Christian Brauner , Christian Lamparter , Chris Zankel , Cong Wang , Daniel Axtens , Daniel Vetter , Dan Williams , David Gow , David Howells , Dennis Dalessandro , devicetree@vger.kernel.org, Dexuan Cui , Dmitry Kasatkin , Eli Cohen , Eric Dumazet , Eugeniu Rosca , Felipe Balbi , Francis Laniel , Frank Rowand , Franky Lin , Greg Kroah-Hartman , Gregory Greenman , Guenter Roeck , Haiyang Zhang , Hante Meuleman , Hulk Robot , Jakub Kicinski , "James E.J. Bottomley" , James Morris , Jarkko Sakkinen , Jaroslav Kysela , Jason Gunthorpe , Jens Axboe , Johan Hedberg , Johannes Berg , Johannes Berg , John Keeping , Juergen Gross , Kalle Valo , Keith Packard , keyrings@vger.kernel.org, kunit-dev@googlegroups.com, Kuniyuki Iwashima , "K. Y. Srinivasan" , Lars-Peter Clausen , Lee Jones , Leon Romanovsky , Liam Girdwood , linux1394-devel@lists.sourceforge.net, linux-afs@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-hardening@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-integrity@vger.kernel.org, linux-rdma@vger.kernel.org, linux-scsi@vger.kernel.org, linux-security-module@vger.kernel.org, linux-usb@vger.kernel.org, linux-wireless@vger.kernel.org, linux-xtensa@linux-xtensa.org, llvm@lists.linux.dev, Loic Poulain , Louis Peens , Luca Coelho , Luiz Augusto von Dentz , Marc Dionne , Marcel Holtmann , Mark Brown , "Martin K. Petersen" , Max Filippov , Mimi Zohar , Muchun Song , Nathan Chancellor , Nuno =?iso-8859-1?Q?S=E1?= , Paolo Abeni , Rich Felker , Rob Herring , Russell King , "Serge E. Hallyn" , SHA-cyfmac-dev-list@infineon.com, Simon Horman , Stefano Stabellini , Stefan Richter , Stephen Hemminger , Tadeusz Struk , Takashi Iwai , Tom Rix , Udipto Goswami , Vincenzo Frascino , wcn36xx@lists.infradead.org, Wei Liu , xen-devel@lists.xenproject.org, Yang Yingliang Subject: Re: [PATCH 28/32] selinux: Use mem_to_flex_dup() with xfrm and sidtab Message-ID: <202205051124.6D80ABAE32@keescook> References: <20220504014440.3697851-1-keescook@chromium.org> <20220504014440.3697851-29-keescook@chromium.org> <20220504234324.GA12556@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Wed, May 04, 2022 at 11:14:42PM -0400, Paul Moore wrote: > On Wed, May 4, 2022 at 7:34 PM Gustavo A. R. Silva > wrote: > > > > Hi Paul, > > > > On Wed, May 04, 2022 at 06:57:28PM -0400, Paul Moore wrote: > > > On Tue, May 3, 2022 at 9:57 PM Kees Cook wrote: > > > > [..] > > > > > > +++ b/include/uapi/linux/xfrm.h > > > > @@ -31,9 +31,9 @@ struct xfrm_id { > > > > struct xfrm_sec_ctx { > > > > __u8 ctx_doi; > > > > __u8 ctx_alg; > > > > - __u16 ctx_len; > > > > + __DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(__u16, ctx_len); > > > > __u32 ctx_sid; > > > > - char ctx_str[0]; > > > > + __DECLARE_FLEX_ARRAY_ELEMENTS(char, ctx_str); > > > > }; > > > > > > While I like the idea of this in principle, I'd like to hear about the > > > testing you've done on these patches. A previous flex array > > > conversion in the audit uapi headers ended up causing a problem with > > > > I'm curious about which commit caused those problems...? > > Commit ed98ea2128b6 ("audit: replace zero-length array with > flexible-array member"), however, as I said earlier, the problem was > actually with SWIG, it just happened to be triggered by the kernel > commit. There was a brief fedora-devel mail thread about the problem, > see the link below: > > * https://www.spinics.net/lists/fedora-devel/msg297991.html Wow, that's pretty weird -- it looks like SWIG was scraping the headers to build its conversions? I assume SWIG has been fixed now? > To reiterate, I'm supportive of changes like this, but I would like to > hear how it was tested to ensure there are no unexpected problems with > userspace. If there are userspace problems it doesn't mean we can't > make changes like this, it just means we need to ensure that the > userspace issues are resolved first. Well, as this is the first and only report of any problems with [0] -> [] conversions (in UAPI or anywhere) that I remember seeing, and they've been underway since at least v5.9, I hadn't been doing any new testing. So, for this case, I guess I should ask what tests you think would be meaningful here? Anything using #include should be fine: https://codesearch.debian.net/search?q=linux%2Fxfrm.h&literal=1&perpkg=1 Which leaves just this, which may be doing something weird: libabigail_2.0-1/tests/data/test-diff-filter/test-PR27569-v0.abi But I see that SWIG doesn't show up in a search for linux/audit.h: https://codesearch.debian.net/search?q=linux%2Faudit.h&literal=1&perpkg=1 So this may not be a sufficient analysis... -- Kees Cook