From nobody Tue Dec 16 16:00:02 2025 X-Original-To: dev-commits-src-main@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4dW1ps2qX9z6L8vL; Tue, 16 Dec 2025 16:00:05 +0000 (UTC) (envelope-from cy.schubert@cschubert.com) Received: from omta003.cacentral1.a.cloudfilter.net (omta001.cacentral1.a.cloudfilter.net [3.97.99.32]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "Client", Issuer "CA" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4dW1ps0y0Xz40r4; Tue, 16 Dec 2025 16:00:05 +0000 (UTC) (envelope-from cy.schubert@cschubert.com) Authentication-Results: mx1.freebsd.org; none Received: from shw-obgw-4003b.ext.cloudfilter.net ([10.228.9.157]) by cmsmtp with ESMTPS id VRVUvvqDWAPFJVXT2v6U2l; Tue, 16 Dec 2025 16:00:04 +0000 Received: from spqr.komquats.com ([70.66.136.217]) by cmsmtp with ESMTPSA id VXT0vuLwS24TSVXT1vaWzY; Tue, 16 Dec 2025 16:00:04 +0000 X-Auth-User: cschuber X-Authority-Analysis: v=2.4 cv=Ie+KmGqa c=1 sm=1 tr=0 ts=69418204 a=h7br+8Ma+Xn9xscxy5znUg==:117 a=h7br+8Ma+Xn9xscxy5znUg==:17 a=kj9zAlcOel0A:10 a=wP3pNCr1ah4A:10 a=6I5d2MoRAAAA:8 a=EkcXrb_YAAAA:8 a=VxmjJ2MpAAAA:8 a=pGLkceISAAAA:8 a=YxBL1-UpAAAA:8 a=031C1j8QFwABdqN2fNoA:9 a=CjuIK1q_8ugA:10 a=LK5xJRSDVpKd5WXXoEvA:22 a=7gXAzLPJhVmCkEl4_tsf:22 a=Ia-lj3WSrqcvXOmTRaiG:22 Received: from slippy.cwsent.com (slippy.cwsent.com [10.1.1.91]) by spqr.komquats.com (Postfix) with ESMTP id A78D0234; Tue, 16 Dec 2025 08:00:02 -0800 (PST) Received: by slippy.cwsent.com (Postfix, from userid 1000) id A65D63D6; Tue, 16 Dec 2025 08:00:02 -0800 (PST) X-Mailer: exmh version 2.9.0 11/07/2018 with nmh-1.8+dev Reply-to: Cy Schubert From: Cy Schubert X-os: FreeBSD X-Sender: cy@cwsent.com X-URL: http://www.cschubert.com/ To: Cy Schubert cc: Robert Clausecker , src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: Re: git: 66eb78377bf1 - main - libc/amd64: fix overread conditions in stpncpy() In-reply-to: <20251216135709.46D25203@slippy.cwsent.com> References: <693ee0f1.3662d.650a5e21@gitrepo.freebsd.org> <20251216135709.46D25203@slippy.cwsent.com> Comments: In-reply-to Cy Schubert message dated "Tue, 16 Dec 2025 05:57:09 -0800." List-Id: Commit messages for the main branch of the src repository List-Archive: https://lists.freebsd.org/archives/dev-commits-src-main List-Help: List-Post: List-Subscribe: List-Unsubscribe: X-BeenThere: dev-commits-src-main@freebsd.org Sender: owner-dev-commits-src-main@FreeBSD.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Tue, 16 Dec 2025 08:00:02 -0800 Message-Id: <20251216160002.A65D63D6@slippy.cwsent.com> X-CMAE-Envelope: MS4xfCpCpTU5n7gVDkjPw//yDq9vzrL09Ceto+KwzZ4q2aZNHja8g8MryLabV+1qlcXEY8t89kPJWSE/5EJGAk//RllmcwX+0gwvuj+PA5KEBNs8xAkpzRxI YMfc7f4nMi21AVaDH9pFl6n6/jTiTao9DED4qE7GjqWudEM1Z+YNRQHX9ssbWxKviVr1WX6w6XW0Pr9jxPHIkRluOcgw/w61VNjXDa2RghatiaejlBS6H6pk LPmMKaXc+5U5NKvULfqmj3gsWqqKkiybGnC5FrIrCyFiE6DIgaoBx/I3H/WSVC5pRFNOWCziRAIVehRorVMexmafYDwr63FtnW2KYZDaP2Y= X-Spamd-Bar: ---- X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:16509, ipnet:3.96.0.0/15, country:US] X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Rspamd-Queue-Id: 4dW1ps0y0Xz40r4 In message <20251216135709.46D25203@slippy.cwsent.com>, Cy Schubert writes: > In message <693ee0f1.3662d.650a5e21@gitrepo.freebsd.org>, Robert Clausecker > wri > tes: > > The branch main has been updated by fuz: > > > > URL: https://cgit.FreeBSD.org/src/commit/?id=66eb78377bf109af1d9e25626bf254 > b4 > > 369436ec > > > > commit 66eb78377bf109af1d9e25626bf254b4369436ec > > Author: Robert Clausecker > > AuthorDate: 2025-12-10 20:45:18 +0000 > > Commit: Robert Clausecker > > CommitDate: 2025-12-14 16:06:05 +0000 > > > > libc/amd64: fix overread conditions in stpncpy() > > > > Due to incorrect unit test design, two overread conditions went > > undetected in the amd64 baseline stpncpy() implementation. > > For buffers of 1--16 and 32 bytes that do not contain nul bytes > > and end exactly at a page boundary, the code would incorrectly > > read 16 bytes from the next page, possibly crossing into an > > unmapped page and crashing the program. If the next page was > > mapped, the code would then proceed with the expected behaviour > > of the stpncpy() function. > > > > Three changes were made to fix the bug: > > > > - an off-by-one error is fixed in the code deciding whether to > > enter the runt case or not, entering it for 0 > instead of 0 > - in the runt case, the logic to skip reading a second 16-byte > > chunk if the buffer ends in the first chunk was fixed to > > account for buffers that end at a 16-byte boundary but do not > > hold a nul byte. > > - in the runt case, the logic to transform the location of the > > end of the input buffer into a bit mask was fixed to allow > > the case of n==32, which was previously impossible due to the > > incorrect logic for entering said case. > > > > The performance impact should be minimal. > > > > PR: 291359 > > See also: D54169 > > Reported by: Collin Funk > > Reviewed by: getz > > Approved by: markj (mentor) > > MFC after: 1 week > > Fixes: 90253d49db09a9b1490c448d05314f3e4bbfa468 (D42519) > > Differential Revision: https://reviews.freebsd.org/D54170 > > --- > > lib/libc/amd64/string/stpncpy.S | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/lib/libc/amd64/string/stpncpy.S b/lib/libc/amd64/string/stpncp > y. > > S > > index 5ce0dd093a9e..df22bb9f0c53 100644 > > --- a/lib/libc/amd64/string/stpncpy.S > > +++ b/lib/libc/amd64/string/stpncpy.S > > @@ -100,7 +100,7 @@ ARCHENTRY(__stpncpy, baseline) > > movdqa (%rsi), %xmm0 # load head > > and $0xf, %ecx # offset from alignment > > mov $-1, %r9d > > - lea -32(%rcx), %rax # set up overflow-proof compari > > son rdx+rcx<=32 > > + lea -33(%rcx), %rax # set up overflow-proof compari > > son rdx+rcx<=32 > > shl %cl, %r9d # mask of bytes belonging to th > > e string > > sub %rcx, %rdi # adjust RDI to correspond to R > > SI > > pxor %xmm1, %xmm1 > > @@ -223,8 +223,9 @@ ARCHENTRY(__stpncpy, baseline) > > > > /* 1--32 bytes to copy, bounce through the stack */ > > .Lrunt: movdqa %xmm1, bounce+16(%rsp) # clear out rest of on- > > stack copy > > - bts %r10d, %r8d # treat end of buffer as end of > > string > > - and %r9w, %r8w # end of string within first bu > > ffer? > > + bts %r10, %r8 # treat end of buffer as end of > > string > > + and %r9d, %r8d # mask out head before string > > + test $0x1ffff, %r8d # end of string within first ch > > unk or right after? > > jnz 0f # if yes, do not inspect second > > buffer > > > > movdqa 16(%rsi), %xmm0 # load second chunk of input > > > > I've opened PR/291720 regarding a significant regression caused by this > commit. It affects my older machines, resulting in enviornment (getenv) > corruption. It does not affect my newer (and with more RAM) machines. BTW, this brought my postfix server effectively offline. I have not been able to send or receive email until this commit was reverted locally. -- Cheers, Cy Schubert FreeBSD UNIX: Web: https://FreeBSD.org NTP: Web: https://nwtime.org e**(i*pi)+1=0