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[69.131.150.190]) by smtp.gmail.com with ESMTPSA id 00721157ae682-7bd6656d218sm17775697b3.22.2026.05.01.17.21.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 01 May 2026 17:21:41 -0700 (PDT) Message-ID: Date: Fri, 1 May 2026 20:21:27 -0400 Precedence: bulk X-Mailing-List: iwd@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [oss-security] CVE-2026-31431: CopyFail: linux local privilege scalation To: Eric Biggers Cc: oss-security@lists.openwall.com, Jan Schaumann , iwd@lists.linux.dev References: <87se8dgicq.fsf@gentoo.org> <20260430071917.GB54208@sol> <177abb5d-8ba9-4bb9-8b23-9fbc868ed3cd@gmail.com> <20260501180028.GA2260@sol> <19837ef5-e5b6-45f4-8336-3ce07423dfb1@gmail.com> <20260501201841.GA2540@quark> Content-Language: en-US From: Demi Marie Obenour Autocrypt: addr=demiobenour@gmail.com; keydata= xsFNBFp+A0oBEADffj6anl9/BHhUSxGTICeVl2tob7hPDdhHNgPR4C8xlYt5q49yB+l2nipd aq+4Gk6FZfqC825TKl7eRpUjMriwle4r3R0ydSIGcy4M6eb0IcxmuPYfbWpr/si88QKgyGSV Z7GeNW1UnzTdhYHuFlk8dBSmB1fzhEYEk0RcJqg4AKoq6/3/UorR+FaSuVwT7rqzGrTlscnT DlPWgRzrQ3jssesI7sZLm82E3pJSgaUoCdCOlL7MMPCJwI8JpPlBedRpe9tfVyfu3euTPLPx wcV3L/cfWPGSL4PofBtB8NUU6QwYiQ9Hzx4xOyn67zW73/G0Q2vPPRst8LBDqlxLjbtx/WLR 6h3nBc3eyuZ+q62HS1pJ5EvUT1vjyJ1ySrqtUXWQ4XlZyoEFUfpJxJoN0A9HCxmHGVckzTRl 5FMWo8TCniHynNXsBtDQbabt7aNEOaAJdE7to0AH3T/Bvwzcp0ZJtBk0EM6YeMLtotUut7h2 Bkg1b//r6bTBswMBXVJ5H44Qf0+eKeUg7whSC9qpYOzzrm7+0r9F5u3qF8ZTx55TJc2g656C 9a1P1MYVysLvkLvS4H+crmxA/i08Tc1h+x9RRvqba4lSzZ6/Tmt60DPM5Sc4R0nSm9BBff0N m0bSNRS8InXdO1Aq3362QKX2NOwcL5YaStwODNyZUqF7izjK4QARAQABzTxEZW1pIE1hcmll IE9iZW5vdXIgKGxvdmVyIG9mIGNvZGluZykgPGRlbWlvYmVub3VyQGdtYWlsLmNvbT7CwXgE EwECACIFAlp+A0oCGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJELKItV//nCLBhr8Q AK/xrb4wyi71xII2hkFBpT59ObLN+32FQT7R3lbZRjVFjc6yMUjOb1H/hJVxx+yo5gsSj5LS 9AwggioUSrcUKldfA/PKKai2mzTlUDxTcF3vKx6iMXKA6AqwAw4B57ZEJoMM6egm57TV19kz PMc879NV2nc6+elaKl+/kbVeD3qvBuEwsTe2Do3HAAdrfUG/j9erwIk6gha/Hp9yZlCnPTX+ VK+xifQqt8RtMqS5R/S8z0msJMI/ajNU03kFjOpqrYziv6OZLJ5cuKb3bZU5aoaRQRDzkFIR 6aqtFLTohTo20QywXwRa39uFaOT/0YMpNyel0kdOszFOykTEGI2u+kja35g9TkH90kkBTG+a EWttIht0Hy6YFmwjcAxisSakBuHnHuMSOiyRQLu43ej2+mDWgItLZ48Mu0C3IG1seeQDjEYP tqvyZ6bGkf2Vj+L6wLoLLIhRZxQOedqArIk/Sb2SzQYuxN44IDRt+3ZcDqsPppoKcxSyd1Ny 2tpvjYJXlfKmOYLhTWs8nwlAlSHX/c/jz/ywwf7eSvGknToo1Y0VpRtoxMaKW1nvH0OeCSVJ itfRP7YbiRVc2aNqWPCSgtqHAuVraBRbAFLKh9d2rKFB3BmynTUpc1BQLJP8+D5oNyb8Ts4x Xd3iV/uD8JLGJfYZIR7oGWFLP4uZ3tkneDfYzsFNBFp+A0oBEAC9ynZI9LU+uJkMeEJeJyQ/ 8VFkCJQPQZEsIGzOTlPnwvVna0AS86n2Z+rK7R/usYs5iJCZ55/JISWd8xD57ue0eB47bcJv VqGlObI2DEG8TwaW0O0duRhDgzMEL4t1KdRAepIESBEA/iPpI4gfUbVEIEQuqdqQyO4GAe+M kD0Hy5JH/0qgFmbaSegNTdQg5iqYjRZ3ttiswalql1/iSyv1WYeC1OAs+2BLOAT2NEggSiVO txEfgewsQtCWi8H1SoirakIfo45Hz0tk/Ad9ZWh2PvOGt97Ka85o4TLJxgJJqGEnqcFUZnJJ riwoaRIS8N2C8/nEM53jb1sH0gYddMU3QxY7dYNLIUrRKQeNkF30dK7V6JRH7pleRlf+wQcN fRAIUrNlatj9TxwivQrKnC9aIFFHEy/0mAgtrQShcMRmMgVlRoOA5B8RTulRLCmkafvwuhs6 dCxN0GNAORIVVFxjx9Vn7OqYPgwiofZ6SbEl0hgPyWBQvE85klFLZLoj7p+joDY1XNQztmfA rnJ9x+YV4igjWImINAZSlmEcYtd+xy3Li/8oeYDAqrsnrOjb+WvGhCykJk4urBog2LNtcyCj kTs7F+WeXGUo0NDhbd3Z6AyFfqeF7uJ3D5hlpX2nI9no/ugPrrTVoVZAgrrnNz0iZG2DVx46 x913pVKHl5mlYQARAQABwsFfBBgBAgAJBQJafgNKAhsMAAoJELKItV//nCLBwNIP/AiIHE8b oIqReFQyaMzxq6lE4YZCZNj65B/nkDOvodSiwfwjjVVE2V3iEzxMHbgyTCGA67+Bo/d5aQGj gn0TPtsGzelyQHipaUzEyrsceUGWYoKXYyVWKEfyh0cDfnd9diAm3VeNqchtcMpoehETH8fr RHnJdBcjf112PzQSdKC6kqU0Q196c4Vp5HDOQfNiDnTf7gZSj0BraHOByy9LEDCLhQiCmr+2 E0rW4tBtDAn2HkT9uf32ZGqJCn1O+2uVfFhGu6vPE5qkqrbSE8TG+03H8ecU2q50zgHWPdHM OBvy3EhzfAh2VmOSTcRK+tSUe/u3wdLRDPwv/DTzGI36Kgky9MsDC5gpIwNbOJP2G/q1wT1o Gkw4IXfWv2ufWiXqJ+k7HEi2N1sree7Dy9KBCqb+ca1vFhYPDJfhP75I/VnzHVssZ/rYZ9+5 1yDoUABoNdJNSGUYl+Yh9Pw9pE3Kt4EFzUlFZWbE4xKL/NPno+z4J9aWemLLszcYz/u3XnbO vUSQHSrmfOzX3cV4yfmjM5lewgSstoxGyTx2M8enslgdXhPthZlDnTnOT+C+OTsh8+m5tos8 HQjaPM01MKBiAqdPgksm1wu2DrrwUi6ChRVTUBcj6+/9IJ81H2P2gJk3Ls3AVIxIffLoY34E +MYSfkEjBz0E8CLOcAw7JIwAaeBT In-Reply-To: <20260501201841.GA2540@quark> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------NMvqjR7yB9G5Z77VGoqgNxzT" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------------NMvqjR7yB9G5Z77VGoqgNxzT Content-Type: multipart/mixed; boundary="------------0QVf0uxUmjkLyYkdSuo003iL"; protected-headers="v1" Message-ID: Date: Fri, 1 May 2026 20:21:27 -0400 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [oss-security] CVE-2026-31431: CopyFail: linux local privilege scalation To: Eric Biggers Cc: oss-security@lists.openwall.com, Jan Schaumann , iwd@lists.linux.dev References: <87se8dgicq.fsf@gentoo.org> <20260430071917.GB54208@sol> <177abb5d-8ba9-4bb9-8b23-9fbc868ed3cd@gmail.com> <20260501180028.GA2260@sol> <19837ef5-e5b6-45f4-8336-3ce07423dfb1@gmail.com> <20260501201841.GA2540@quark> Content-Language: en-US From: Demi Marie Obenour Autocrypt: addr=demiobenour@gmail.com; keydata= xsFNBFp+A0oBEADffj6anl9/BHhUSxGTICeVl2tob7hPDdhHNgPR4C8xlYt5q49yB+l2nipd aq+4Gk6FZfqC825TKl7eRpUjMriwle4r3R0ydSIGcy4M6eb0IcxmuPYfbWpr/si88QKgyGSV Z7GeNW1UnzTdhYHuFlk8dBSmB1fzhEYEk0RcJqg4AKoq6/3/UorR+FaSuVwT7rqzGrTlscnT DlPWgRzrQ3jssesI7sZLm82E3pJSgaUoCdCOlL7MMPCJwI8JpPlBedRpe9tfVyfu3euTPLPx wcV3L/cfWPGSL4PofBtB8NUU6QwYiQ9Hzx4xOyn67zW73/G0Q2vPPRst8LBDqlxLjbtx/WLR 6h3nBc3eyuZ+q62HS1pJ5EvUT1vjyJ1ySrqtUXWQ4XlZyoEFUfpJxJoN0A9HCxmHGVckzTRl 5FMWo8TCniHynNXsBtDQbabt7aNEOaAJdE7to0AH3T/Bvwzcp0ZJtBk0EM6YeMLtotUut7h2 Bkg1b//r6bTBswMBXVJ5H44Qf0+eKeUg7whSC9qpYOzzrm7+0r9F5u3qF8ZTx55TJc2g656C 9a1P1MYVysLvkLvS4H+crmxA/i08Tc1h+x9RRvqba4lSzZ6/Tmt60DPM5Sc4R0nSm9BBff0N m0bSNRS8InXdO1Aq3362QKX2NOwcL5YaStwODNyZUqF7izjK4QARAQABzTxEZW1pIE1hcmll IE9iZW5vdXIgKGxvdmVyIG9mIGNvZGluZykgPGRlbWlvYmVub3VyQGdtYWlsLmNvbT7CwXgE EwECACIFAlp+A0oCGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJELKItV//nCLBhr8Q AK/xrb4wyi71xII2hkFBpT59ObLN+32FQT7R3lbZRjVFjc6yMUjOb1H/hJVxx+yo5gsSj5LS 9AwggioUSrcUKldfA/PKKai2mzTlUDxTcF3vKx6iMXKA6AqwAw4B57ZEJoMM6egm57TV19kz PMc879NV2nc6+elaKl+/kbVeD3qvBuEwsTe2Do3HAAdrfUG/j9erwIk6gha/Hp9yZlCnPTX+ VK+xifQqt8RtMqS5R/S8z0msJMI/ajNU03kFjOpqrYziv6OZLJ5cuKb3bZU5aoaRQRDzkFIR 6aqtFLTohTo20QywXwRa39uFaOT/0YMpNyel0kdOszFOykTEGI2u+kja35g9TkH90kkBTG+a EWttIht0Hy6YFmwjcAxisSakBuHnHuMSOiyRQLu43ej2+mDWgItLZ48Mu0C3IG1seeQDjEYP tqvyZ6bGkf2Vj+L6wLoLLIhRZxQOedqArIk/Sb2SzQYuxN44IDRt+3ZcDqsPppoKcxSyd1Ny 2tpvjYJXlfKmOYLhTWs8nwlAlSHX/c/jz/ywwf7eSvGknToo1Y0VpRtoxMaKW1nvH0OeCSVJ itfRP7YbiRVc2aNqWPCSgtqHAuVraBRbAFLKh9d2rKFB3BmynTUpc1BQLJP8+D5oNyb8Ts4x Xd3iV/uD8JLGJfYZIR7oGWFLP4uZ3tkneDfYzsFNBFp+A0oBEAC9ynZI9LU+uJkMeEJeJyQ/ 8VFkCJQPQZEsIGzOTlPnwvVna0AS86n2Z+rK7R/usYs5iJCZ55/JISWd8xD57ue0eB47bcJv VqGlObI2DEG8TwaW0O0duRhDgzMEL4t1KdRAepIESBEA/iPpI4gfUbVEIEQuqdqQyO4GAe+M kD0Hy5JH/0qgFmbaSegNTdQg5iqYjRZ3ttiswalql1/iSyv1WYeC1OAs+2BLOAT2NEggSiVO txEfgewsQtCWi8H1SoirakIfo45Hz0tk/Ad9ZWh2PvOGt97Ka85o4TLJxgJJqGEnqcFUZnJJ riwoaRIS8N2C8/nEM53jb1sH0gYddMU3QxY7dYNLIUrRKQeNkF30dK7V6JRH7pleRlf+wQcN fRAIUrNlatj9TxwivQrKnC9aIFFHEy/0mAgtrQShcMRmMgVlRoOA5B8RTulRLCmkafvwuhs6 dCxN0GNAORIVVFxjx9Vn7OqYPgwiofZ6SbEl0hgPyWBQvE85klFLZLoj7p+joDY1XNQztmfA rnJ9x+YV4igjWImINAZSlmEcYtd+xy3Li/8oeYDAqrsnrOjb+WvGhCykJk4urBog2LNtcyCj kTs7F+WeXGUo0NDhbd3Z6AyFfqeF7uJ3D5hlpX2nI9no/ugPrrTVoVZAgrrnNz0iZG2DVx46 x913pVKHl5mlYQARAQABwsFfBBgBAgAJBQJafgNKAhsMAAoJELKItV//nCLBwNIP/AiIHE8b oIqReFQyaMzxq6lE4YZCZNj65B/nkDOvodSiwfwjjVVE2V3iEzxMHbgyTCGA67+Bo/d5aQGj gn0TPtsGzelyQHipaUzEyrsceUGWYoKXYyVWKEfyh0cDfnd9diAm3VeNqchtcMpoehETH8fr RHnJdBcjf112PzQSdKC6kqU0Q196c4Vp5HDOQfNiDnTf7gZSj0BraHOByy9LEDCLhQiCmr+2 E0rW4tBtDAn2HkT9uf32ZGqJCn1O+2uVfFhGu6vPE5qkqrbSE8TG+03H8ecU2q50zgHWPdHM OBvy3EhzfAh2VmOSTcRK+tSUe/u3wdLRDPwv/DTzGI36Kgky9MsDC5gpIwNbOJP2G/q1wT1o Gkw4IXfWv2ufWiXqJ+k7HEi2N1sree7Dy9KBCqb+ca1vFhYPDJfhP75I/VnzHVssZ/rYZ9+5 1yDoUABoNdJNSGUYl+Yh9Pw9pE3Kt4EFzUlFZWbE4xKL/NPno+z4J9aWemLLszcYz/u3XnbO vUSQHSrmfOzX3cV4yfmjM5lewgSstoxGyTx2M8enslgdXhPthZlDnTnOT+C+OTsh8+m5tos8 HQjaPM01MKBiAqdPgksm1wu2DrrwUi6ChRVTUBcj6+/9IJ81H2P2gJk3Ls3AVIxIffLoY34E +MYSfkEjBz0E8CLOcAw7JIwAaeBT In-Reply-To: <20260501201841.GA2540@quark> --------------0QVf0uxUmjkLyYkdSuo003iL Content-Type: multipart/mixed; boundary="------------w4C00V60bApXcn0Va6koytM9" --------------w4C00V60bApXcn0Va6koytM9 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 5/1/26 16:18, Eric Biggers wrote: > On Fri, May 01, 2026 at 03:24:51PM -0400, Demi Marie Obenour wrote: >> On 5/1/26 14:00, Eric Biggers wrote: (snip)=20 >>> But people need to help. Send patches to iwd, bluez, cryptsetup, etc= =2E >>> that make them use userspace crypto libraries instead of AF_ALG and >>> KEYCTL_PKEY_*. If the maintainers aren't convinced yet, then patch >>> downstream in your distro as a starting point (and disable the UAPIs = in >>> your kernel). Or help in other ways like writing blog posts that >>> promote attack surface reduction and the alternatives to these UAPIs.= >>> >>> I'd also like to explore some more incremental approaches, such as >>> making these UAPIs require CAP_SYS_ADMIN, possibly configurable by a >>> sysctl. If anyone knows of anything important that would be broken b= y a >>> CAP_SYS_ADMIN requirement on AF_ALG and KEYCTL_PKEY_*, let me know. >> >> Cryptsetup needs CAP_SYS_ADMIN, but iwd definitely does not, and >> presumably BlueZ should not use have it either. >> >> Cryptsetup is a special case because there are times when it may not >> be safe to allocate memory: if I/O to the swap partition is suspended,= >> and the kernel tries to page data out to it, the system may deadlock. >> So calling into arbitrary third-party libraries might not be the best >> idea. Thankfully, Nettle should meet all of cryptsetup's requirements= =2E >=20 > Cryptsetup only uses AF_ALG for certain operations like keyslot > encryption, and only in certain cases: Cryptsetup's default settings > work fine with all CONFIG_CRYPTO_USER_API_* options disabled in the > kernel. The actual I/O to/from encrypted partitions is handled by > dm-crypt in the kernel and has nothing to do with AF_ALG. >=20 > Cryptsetup even already supports userspace crypto libraries as well. I= t > seems there are just some gaps in how it's using them. For example for= > AES-GCM it seems to just go directly to AF_ALG, despite the cryptsetup > binary already being linked to OpenSSL, which means a complete userspac= e > implementation of AES-GCM is already present in its address space! That's really annoying, yikes! >>> I think there should also be an allowlist of algorithms, and the spli= ce >>> support should be removed. (Interestingly, there's precedent for >>> removing splice support from AF_ALG: it was already removed from the = 6.1 >>> LTS kernel last year, seemingly accidentally. That's why the copy.fa= il >>> exploit didn't work on 6.1 but did work on other versions.) >>> >>> - Eric >> >> Would an allowlist and removing splice support allow migrating to >> the crypto library code? I looked at the list of CVEs you provided, >> and I think it would prevent most of the recent ones. The crypto >> library is (as you pointed out) so much easier to use. >=20 > I'm hoping that at least some of these ideas for attack surface > reduction (requiring CAP_SYS_ADMIN, allowlisting the algorithms, > removing splice support) can be implemented in parallel without waiting= > for every userspace program to stop using these UAPIs. Full removal > needs to be the goal, though. CAP_SYS_ADMIN isn't going to be an option for iwd at least. Requiring a Wi-Fi daemon to run as root would be counterproductive. A more flexible option would be to require membership in a specific group, which isn't equivalent to full root privileges. I think the single biggest hardening win for AF_ALG would be to move to the crypto library. The recent CVEs you mentioned mostly seem to relate to the crypto API, and with a hard-coded list of allowed algorithms there's no need to use the crypto API anymore. I'm not familiar enough with kernel code to do this easily, but for anyone with basic knowledge of the existing code it should (hopefully) be straightforward. In the meantime, only using synchronous algorithms and not using hardware drivers would also be a useful simplification. The latter would make it especially clear that AF_ALG is deprecated, because its one potential advantage (being able to use hardware acceleration) would no longer be present. >> Also CCing the iwd mailing list. iwd uses the kernel crypto APIs >> wherever possible, which is a serious problem. However, it already >> needs to perform cryptography in userspace because of ECC. >> >> Nettle provides trivial no-allocation cryptographic APIs. Nettle's >> licensing (LGPLv3+ or GPLv2+) might prevent this, though. OpenSSL has= >> a horrible API, but AWS-LC has a much better one. It also implements >> TLS, which would might allow iwd to get rid of its built-in TLS code >> for EAP-TLS. >=20 > It's unfortunate that the situation with userspace crypto libraries is > fragmented, with the de facto standard one (OpenSSL) not being all that= > great. But that's no excuse to say "put it all in the kernel". Even > using OpenSSL would still be much better. >=20 > - Eric I think there *might* be embedded systems that simply cannot use OpenSSL because the memory (RAM and/or flash) needed for it simply is not there. 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