[{"id":3676739,"web_url":"http://patchwork.ozlabs.org/comment/3676739/","msgid":"<58f27c58-e782-4c4d-8929-cde1f275dea7@redhat.com>","list_archive_url":null,"date":"2026-04-13T13:18:39","subject":"Re: [PATCH] posix: fix false regex match with backrefs and $ anchor","submitter":{"id":22438,"url":"http://patchwork.ozlabs.org/api/people/22438/","name":"Carlos O'Donell","email":"carlos@redhat.com"},"content":"On 4/12/26 3:39 PM, Collin Funk wrote:\n> This fixes the $ anchor being ignored in the following grep command:\n> \n> $ grep -E '^(.?)(.?).?\\2\\1$' <<< ab\n> ab\n> \n> However, the regular expression should only match palindromes.\n> \n> This patch is mostly copied from a commit in Gnulib from Jim Meyering\n> [1]. It was found by Ed Morton in GNU sed [2].\n> \n> [1] https://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commit;h=8c22765403cc34e87ad953cb3f6901e723c937f5\n> [2] https://bugs.gnu.org/68725\n\nMay you please file a glibc bug for this so we can track?\n\nDo you think this would have security impact?","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","libc-alpha@sourceware.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","libc-alpha@sourceware.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=Sd7IDAog;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org\n (client-ip=2620:52:6:3111::32; helo=vm01.sourceware.org;\n envelope-from=libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org;\n receiver=patchwork.ozlabs.org)","sourceware.org;\n\tdkim=pass (1024-bit key,\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=Sd7IDAog","sourceware.org; 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charset=UTF-8; format=flowed","Content-Transfer-Encoding":"7bit","X-BeenThere":"libc-alpha@sourceware.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Libc-alpha mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org"}},{"id":3676855,"web_url":"http://patchwork.ozlabs.org/comment/3676855/","msgid":"<87pl42lrdk.fsf@gmail.com>","list_archive_url":null,"date":"2026-04-13T17:08:55","subject":"Re: [PATCH] posix: fix false regex match with backrefs and $ anchor","submitter":{"id":88687,"url":"http://patchwork.ozlabs.org/api/people/88687/","name":"Collin Funk","email":"collin.funk1@gmail.com"},"content":"Carlos O'Donell writes:\n\n> On 4/12/26 3:39 PM, Collin Funk wrote:\n>> This fixes the $ anchor being ignored in the following grep command:\n>> $ grep -E '^(.?)(.?).?\\2\\1$' <<< ab\n>> ab\n>> However, the regular expression should only match palindromes.\n>> This patch is mostly copied from a commit in Gnulib from Jim\n>> Meyering\n>> [1]. It was found by Ed Morton in GNU sed [2].\n>> [1]\n>> https://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commit;h=8c22765403cc34e87ad953cb3f6901e723c937f5\n>> [2] https://bugs.gnu.org/68725\n>\n> May you please file a glibc bug for this so we can track?\n\nSure, I opened one now [1].\n\n> Do you think this would have security impact?\n\nProbably, since it is a false match. Though, in practice I'm not sure\nhow severe it is. I'm not sure how many security sensitive applications\nare using backreferences like this.\n\nCollin\n\n[1] https://sourceware.org/bugzilla/show_bug.cgi?id=34073","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","libc-alpha@sourceware.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","libc-alpha@sourceware.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=pN15cQtN;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org\n (client-ip=2620:52:6:3111::32; helo=vm01.sourceware.org;\n envelope-from=libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org;\n receiver=patchwork.ozlabs.org)","sourceware.org;\n\tdkim=pass (2048-bit key,\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=pN15cQtN","sourceware.org;\n dmarc=pass (p=none dis=none) header.from=gmail.com","sourceware.org; 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a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1776102023;\n h=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n to:to:cc:cc:mime-version:mime-version:content-type:content-type:\n in-reply-to:in-reply-to:references:references;\n bh=BKW9Cne0DdrM5gibpjjnesM3bUk1vpTL6vF9H/OIrCc=;\n b=TuCi3gSnBfQE/plzlAoad/ZN2j7F/sAOT+zqC4UPEVJCS+nVuwPrhppAjX/0VJLqGBN0cQ\n Td95l6bBmfQNqbttayOGyAk3KBs/4+I1qZxg6SYOR8J+YzqpRujhkhxaZgtxAapLfRO806\n 4tkd66VQ9+ut35TVX0d9nIfRAjgYxsM=","X-MC-Unique":"oBPzqwaOPd6QuEqXT0kxIQ-1","X-Mimecast-MFC-AGG-ID":"oBPzqwaOPd6QuEqXT0kxIQ_1776102018","From":"Florian Weimer ","To":"Collin Funk ","Cc":"libc-alpha@sourceware.org, Jim Meyering , Paul\n Eggert ","Subject":"Re: [PATCH] posix: fix false regex match with backrefs and $ anchor","In-Reply-To":"\n <01d8d5b649d0ce7ad68debec90e86bd9d4838266.1776022765.git.collin.funk1@gmail.com>\n (Collin Funk's message of \"Sun, 12 Apr 2026 12:39:25 -0700\")","References":"\n <01d8d5b649d0ce7ad68debec90e86bd9d4838266.1776022765.git.collin.funk1@gmail.com>","Date":"Mon, 13 Apr 2026 19:40:13 +0200","Message-ID":"","User-Agent":"Gnus/5.13 (Gnus v5.13)","MIME-Version":"1.0","X-Scanned-By":"MIMEDefang 3.4.1 on 10.30.177.4","X-Mimecast-Spam-Score":"0","X-Mimecast-MFC-PROC-ID":"7FI5Q0zmCpJkrWBYdxR5yYWDGSZN1Zgcuz8_eukQyUw_1776102018","X-Mimecast-Originator":"redhat.com","Content-Type":"text/plain","X-BeenThere":"libc-alpha@sourceware.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Libc-alpha mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org"}},{"id":3676913,"web_url":"http://patchwork.ozlabs.org/comment/3676913/","msgid":"<79c0c3cf-3fb7-4100-9c49-bfa9afcf8bc1@cs.ucla.edu>","list_archive_url":null,"date":"2026-04-13T20:29:12","subject":"Re: [PATCH] posix: fix false regex match with backrefs and $ anchor","submitter":{"id":4434,"url":"http://patchwork.ozlabs.org/api/people/4434/","name":"Paul Eggert","email":"eggert@CS.UCLA.EDU"},"content":"On 2026-04-13 10:40, Florian Weimer wrote:\n> Wouldn't it make sense to call check_halt_state_context only once?\n\nYes it would, and thanks. I installed the attached into Gnulib, and we \nshould propagate this into glibc when we propagate the other fixes.","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","libc-alpha@sourceware.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","libc-alpha@sourceware.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=cs.ucla.edu header.i=@cs.ucla.edu header.a=rsa-sha256\n header.s=9D0B346E-2AEB-11ED-9476-E14B719DCE6C header.b=Ccg+Ykul;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org\n (client-ip=2620:52:6:3111::32; helo=vm01.sourceware.org;\n envelope-from=libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org;\n receiver=patchwork.ozlabs.org)","sourceware.org;\n\tdkim=pass (2048-bit key,\n unprotected) header.d=cs.ucla.edu header.i=@cs.ucla.edu header.a=rsa-sha256\n header.s=9D0B346E-2AEB-11ED-9476-E14B719DCE6C header.b=Ccg+Ykul","sourceware.org;\n dmarc=pass (p=none dis=none) header.from=cs.ucla.edu","sourceware.org; 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boundary=\"------------tnTw6R6eewWG7YB90mzHsYuP\"","Message-ID":"<79c0c3cf-3fb7-4100-9c49-bfa9afcf8bc1@cs.ucla.edu>","Date":"Mon, 13 Apr 2026 13:29:12 -0700","MIME-Version":"1.0","User-Agent":"Mozilla Thunderbird","Subject":"Re: [PATCH] posix: fix false regex match with backrefs and $ anchor","To":"Florian Weimer ","Cc":"libc-alpha@sourceware.org, Jim Meyering ,\n Gnulib bugs , Collin Funk ","References":"\n <01d8d5b649d0ce7ad68debec90e86bd9d4838266.1776022765.git.collin.funk1@gmail.com>\n ","Content-Language":"en-US","From":"Paul Eggert ","Autocrypt":"addr=eggert@cs.ucla.edu; keydata=\n xsFNBEyAcmQBEADAAyH2xoTu7ppG5D3a8FMZEon74dCvc4+q1XA2J2tBy2pwaTqfhpxxdGA9\n Jj50UJ3PD4bSUEgN8tLZ0san47l5XTAFLi2456ciSl5m8sKaHlGdt9XmAAtmXqeZVIYX/UFS\n 96fDzf4xhEmm/y7LbYEPQdUdxu47xA5KhTYp5bltF3WYDz1Ygd7gx07Auwp7iw7eNvnoDTAl\n KAl8KYDZzbDNCQGEbpY3efZIvPdeI+FWQN4W+kghy+P6au6PrIIhYraeua7XDdb2LS1en3Ss\n mE3QjqfRqI/A2ue8JMwsvXe/WK38Ezs6x74iTaqI3AFH6ilAhDqpMnd/msSESNFt76DiO1ZK\n QMr9amVPknjfPmJISqdhgB1DlEdw34sROf6V8mZw0xfqT6PKE46LcFefzs0kbg4GORf8vjG2\n Sf1tk5eU8MBiyN/bZ03bKNjNYMpODDQQwuP84kYLkX2wBxxMAhBxwbDVZudzxDZJ1C2VXujC\n OJVxq2kljBM9ETYuUGqd75AW2LXrLw6+MuIsHFAYAgRr7+KcwDgBAfwhPBYX34nSSiHlmLC+\n KaHLeCLF5ZI2vKm3HEeCTtlOg7xZEONgwzL+fdKo+D6SoC8RRxJKs8a3sVfI4t6CnrQzvJbB\n n6gxdgCu5i29J1QCYrCYvql2UyFPAK+do99/1jOXT4m2836j1wARAQABzSBQYXVsIEVnZ2Vy\n dCA8ZWdnZXJ0QGNzLnVjbGEuZWR1PsLBlQQTAQgAPwIbAwYLCQgHAwIGFQgCCQoLBBYCAwEC\n HgECF4AWIQR+N5Kp2Kz31jO8FYjtl+kOYqp+NAUCabswsgUJHxsOjAAKCRDtl+kOYqp+NJlw\n D/9OSN9yKUVlhMG0/k9WfOogQbifE5TmYZ/9Iyl1l1hRURXNqeFDX8S0yme1c+++/61jl85V\n Xt+Fv8UzUpULvmPcIetf1vWZeHysbHJ1ZOHIMWnf7C9gxEbne+z90B51QTRCYcOlBHvuVeS0\n DbaSJf2A41Bnsaa4DGpcTG6pzgGZLIpA6YOMDLC+pif1jiwieJp67Xj6oggzckKuOeD3pdKO\n hL7hLkzCFyWvIwnUOZWQp15w3pklQpSL7+yudfnlHuuG+As6zjHdz/51/vQJIb7keScZSmSC\n I76NEIrCPr7bIksZADLD8y/HnlzbWO+uUnKK4SvfnILLkp4o4ODZH1gjbZZDqFi1HawyWbYL\n lCU3k6I9MSWiLU7IafhMIaVf+oUcomA4Sa/H15dLaxQ0UkkUpSG8CqfU2ffFMUm7b/6GecOf\n y7WI4IztYzKV2rtT+OuzuHlc3uDCRthN84WggEsDbfHvIvXmYQG660W90qPxfB54ddi+SoEW\n RP0VkEIJm29rkbcz7apR2Y0i9BQk736khBQ6cT5G7INlmnkFv2jw3Z3lwAbUuvVsjMZBfELY\n iiQtP8fJbXQ7P5FTCqN+u6G2TPTMzwfvPIsrmNpM6/iwAu8b3y239ZxV6Vm1K5uYywjcL3z8\n kLO7Zx1/ajPFOFd4oW1cPlFnMZCBBY7DYwtH8s7BTQRMgHJkARAApoXrvxP3DIfjCNOtXU/P\n dwMShKdX/RlSs5PfunV1wbKP8herXHrvQdFVqECaTSxmlhzbk8X0PkY9gcVaU2O49T3qsOd1\n cHeF52YFGEt0LhsBeMjgNX5uZ1V76r8gyeVlFpWWb0SIwJUBHrDXexF67upeRb2vdHBjYDNe\n ySn+0B7gFEqvVmZu+LadudDp6kQLjatFvHQHUSGNshBnkkcaTbiI9Pst0GCc2aiznBiPPA2W\n QxAPlPRh3OGTsn5THADmbjqY6FEMLasVX8DSCblMvLwNeO/8SxziBidhqLpJCqdQRWHku5Xx\n gIkGeKOz5OLDvXHWJyafrEYjjkS6Ak6B5z6svKliClWnjHQcjlPzyoFFgKTEfcqDxCj4RY0D\n 0DgtFD0NfyeOidrSB/SzTe2hwryQE3rpSiqo+0cGdzh4yAHKYJ+UrXZ4p93ZhjGfKD1xlrNY\n DlWyW9PGmbvqFuDmiIAQf9WD/wzEfICc+F+uDDI+uYkRxUFp92ykmdhDEFg1yjYsU8iGU69a\n Hyvhq36z4zctvbqhRNzOWB1bVJ/dIMDvsExGcXQVDIT7sDNXv0wE3jKSKpp7NDG1oXUXL+2+\n SF99Kjy753AbQSAmH617fyBNwhJWvQYg+mUvPpiGOtses9EXUI3lS4v0MEaPG43flEs1UR+1\n rpFQWVHo1y1OO+sAEQEAAcLBfAQYAQgAJgIbDBYhBH43kqnYrPfWM7wViO2X6Q5iqn40BQJp\n uzCyBQkfGw6MAAoJEO2X6Q5iqn40Q5IQAIyyh3N1m6LgSN2Rf86kLL2ICijK3cPH9l0KvwWL\n SZ7GwkAQCsz4w5C3LYcPqY5BtCrwSaHH0Wv3EcQPy3vqXf/8dR+d5K3171HDx4YD9182G4sp\n 8ENKwqZB1At7DUDtS7ogOME3Jou+5ExKEIoTBgrFOkVW7dhpiRLH3p3Mbchlt+UBkjdGEE+7\n 3L1ttcGvEImBsN01oMYqgmVj5unwD7fwPXN56aLpBylRrlmvuxZyQVRvC1y2vJqIWJ7a2HhF\n 8C03O6oi8OhCQwoyqnpRTeRJb+kcIFj5RDw8v4W6T1LWtw7z6q+zYmvzhNbvwX5pvadWlFj6\n 3RPvfcJY6+RyuyMNPio1yhYakJKpvxJVpSsIbPyeEeiPez6dLl8/CMH4p8P3p0W+EmfENreR\n HfbOv5hXuAnR2eD/DzNrrIVRRjiFoEaYlKj5SDTNTsRjzrgTnSlE9eldkakIoxn9cQ/oD+mx\n 3dSD/vuWZ2v/RroxxxT9PJiLEPg2/Z8R3VL9Ff+RzCUIql6cY4NG7/mkU/Ed6u55S9IWcSI8\n vFBto2TvYSv1woVRiF6rR0fWhY47BLweQwaK5vJa8XnvB7xFY/91Zll1P3z7iBaxg6GstGIl\n 9bIIO73BetYMj1ZvNgz2I6lsrpWQDYa/81II3XsGG/etr63vzAAY3wb4QAPYTZQKKey3","Organization":"UCLA Computer Science Department","In-Reply-To":"","X-BeenThere":"libc-alpha@sourceware.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Libc-alpha mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org"}},{"id":3676932,"web_url":"http://patchwork.ozlabs.org/comment/3676932/","msgid":"<878qaqlflf.fsf@gmail.com>","list_archive_url":null,"date":"2026-04-13T21:23:24","subject":"Re: [PATCH] posix: fix false regex match with backrefs and $ anchor","submitter":{"id":88687,"url":"http://patchwork.ozlabs.org/api/people/88687/","name":"Collin Funk","email":"collin.funk1@gmail.com"},"content":"Dropping bug-gnulib, since my message doesn't apply there.\n\nPaul Eggert writes:\n\n> On 2026-04-13 10:40, Florian Weimer wrote:\n>> Wouldn't it make sense to call check_halt_state_context only once?\n>\n> Yes it would, and thanks. I installed the attached into Gnulib, and we\n> should propagate this into glibc when we propagate the other fixes.\n\nThanks, I had planned to send the other fixes separately with bug\nreports after this one. I figured glibc would prefer things that way.\n\nI submitted a v2 with your adjustments [1]. In case anyone is wondering\nwhy the links it my commit messages lead to nowhere, GNU's cgit and\ngitweb interfaces haven't picked up commits since a week ago. They\nshould work once that is fixed. I sent a message to\nsavannah-hackers-public.\n\nCollin\n\n[1] https://inbox.sourceware.org/libc-alpha/d2fb83f75b54b6be662a2501bc3c6a2d68dfd0b0.1776115137.git.collin.funk1@gmail.com/T/#u","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","libc-alpha@sourceware.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","libc-alpha@sourceware.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=gbW+j2W4;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org\n (client-ip=2620:52:6:3111::32; helo=vm01.sourceware.org;\n envelope-from=libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org;\n receiver=patchwork.ozlabs.org)","sourceware.org;\n\tdkim=pass (2048-bit key,\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=gbW+j2W4","sourceware.org;\n dmarc=pass (p=none dis=none) header.from=gmail.com","sourceware.org; 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It was found by Ed Morton in GNU sed [2].\n>>> [1]\n>>> https://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commit;h=8c22765403cc34e87ad953cb3f6901e723c937f5\n>>> [2] https://bugs.gnu.org/68725\n>>\n>> May you please file a glibc bug for this so we can track?\n>\n> Sure, I opened one now [1].\n>\n>> Do you think this would have security impact?\n>\n> Probably, since it is a false match. Though, in practice I'm not sure\n> how severe it is. I'm not sure how many security sensitive applications\n> are using backreferences like this.\n\nI think we've quite a few bugs like this, and none of the seemed to have\nsecurity implications in actual applications. We need to draw a line\nsomewhere. If every bug becomes a security vulnerability, the\ndistinction becomes meaningless.\n\nThanks,\nFlorian","headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","libc-alpha@sourceware.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","libc-alpha@sourceware.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=YHWFq3sA;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org\n (client-ip=2620:52:6:3111::32; helo=vm01.sourceware.org;\n envelope-from=libc-alpha-bounces~incoming=patchwork.ozlabs.org@sourceware.org;\n receiver=patchwork.ozlabs.org)","sourceware.org;\n\tdkim=pass (1024-bit key,\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=YHWFq3sA","sourceware.org; dmarc=pass (p=quarantine dis=none)\n header.from=redhat.com","sourceware.org; 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