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Thu, 11 Jul 2024 13:47:12 -0700 (PDT) MIME-Version: 1.0 References: <20240118133504.2910955-1-shy828301@gmail.com> <2d7bd8b2b9736d4a7d0a26169978372b5e002a62.camel@debian.org> In-Reply-To: <2d7bd8b2b9736d4a7d0a26169978372b5e002a62.camel@debian.org> From: Yang Shi Date: Thu, 11 Jul 2024 13:47:00 -0700 Message-ID: Subject: Re: [PATCH] mm: huge_memory: don't force huge page alignment on 32 bit To: Yves-Alexis Perez Cc: jirislaby@kernel.org, surenb@google.com, riel@surriel.com, willy@infradead.org, cl@linux.com, akpm@linux-foundation.org, yang@os.amperecomputing.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Salvatore Bonaccorso , Ben Hutchings Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: AE0B54000C X-Stat-Signature: aj4gdgh1f8kkikih5ncb611et544doez X-HE-Tag: 1720730834-313643 X-HE-Meta: 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 4QA7NK8D iWS0sfybdoepUhlKBNgN6AS7Qnta4wkubppsMIj+x+asQCRDhxyEFv1flhlKSssXlDJy+YTVh038a01s6ZH505if5owKsepHJkLD63u7aodnugScyQBrxnbfxHCPNFUrjMAxkLI9YhQ/Pu4X2wFespI19uAf1pNqVOG6P/4uZNsp04/PomnejLjy0xiMOSnVd5k1LqlKgDukQ6PEvhWsqYjPWSDG5RbaDTk0jF8RGtPbGE+d/cB+hhYmael3PLBKihlfvXP/vFp+Fu2GHmkR+rlEvVEmrSKPMIz0Cs1TRWbDkLkjyDuvl9Cv9nFUxFHbhX6F8AHseRF+iRnRDAQcbXqVnM19Fk+IcADpX3w67p3qa/Rz1j2N1fnmoeiyO6sW3ec6MdYMx+/3kXDJ7HTXqs/UPdRbbTg7WEnRzPJRncqRkHG3Cds4gmT0Z6jdrjbBML5/c0R4FXSkssa0JBe3hWrnLig== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000107, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 11, 2024 at 1:10=E2=80=AFPM Yves-Alexis Perez wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA256 > > On Thu, 2024-01-18 at 05:35 -0800, Yang Shi wrote: > > The commit efa7df3e3bb5 ("mm: align larger anonymous mappings on THP > > boundaries") caused two issues [1] [2] reported on 32 bit system or com= pat > > userspace. > > > > It doesn't make too much sense to force huge page alignment on 32 bit > > system due to the constrained virtual address space. > > Hi people, > > sorry for beeing so late. I've looked at this following the OpenSSH issue > (CVE-2024-6387 [1]) and especially the impact on IA-32 installations wher= e > ASLR is apparently broken. > > There was a recent thread [2] on oss-security discussing the issue. > > Looking at the commit log I think the intention was to fix this both for: > - - 32 bit process running on 64 bit kernels: in_compat_syscall() > - - all processes running on 32 bit kernels: IS_ENABLED(CONFIG_32BIT) Yes. It is supposed to cover all 32 bit machines. > > Unfortunately, as far as I can tell, CONFIG_32BIT is not enabled on 32bit= x86 > kernels. Maybe CONFIG_X86_32 would be the right one there? I have not been working on 32 bit machine for years. I'm a little bit surprised CONFIG_32BIT is not enough for x86_32. Sorry for overlooking this. The below patch should fix your problem. diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 2120f7478e55..2944b3fc88a5 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -857,7 +857,8 @@ static unsigned long __thp_get_unmapped_area(struct file *filp, loff_t off_align =3D round_up(off, size); unsigned long len_pad, ret, off_sub; - if (IS_ENABLED(CONFIG_32BIT) || in_compat_syscall()) + if (IS_ENABLED(CONFIG_32BIT) || IS_ENABLED(CONFIG_X86_32) || + in_compat_syscall()) return 0; if (off_end <=3D off_align || (off_end - off_align) < size) > > [1] https://www.openwall.com/lists/oss-security/2024/07/01/3 > [2] https://www.openwall.com/lists/oss-security/2024/07/08/3 > - -- > Yves-Alexis > -----BEGIN PGP SIGNATURE----- > > iQEzBAEBCAAdFiEE8vi34Qgfo83x35gF3rYcyPpXRFsFAmaQPCQACgkQ3rYcyPpX > RFvSHQf/VE7td7scTTsrK7Cx0F3MmDLFgjUDbMDuyPq6lNQqnDbd2zc00JP1eeLs > /mW1uZNbR92bn6xq2sPJu7c6tB3MJuiQme+ZqnPfIgyoWc89i6V6WUXTZN077lIl > xJZxHLMei5KreHz66AYU66HdU89knMTcX362YyyI8dEZKXS3FlP0SLSoBM0UKY0G > HYM6+GetE+fINhfNSMpHgqkTQB825Vqdq5UBsBjHYMg5RJ92/fDgUo5RD7qm/HVz > SDDNSGwpVwYZ20RnnD+DOS9rsnyR4FcAP0m0dcTmQdM8GcY4SyjnEux5idvCicjy > a1jmvsSLxCMZ9mZsrsipIZoNhSHlDA=3D=3D > =3Df0Lk > -----END PGP SIGNATURE-----