Date: Thu, 8 Feb 2018 08:36:38 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Steven Hartland <steven.hartland@multiplay.co.uk>, src-committers@FreeBSD.org, svn-src-all@FreeBSD.org, svn-src-head@FreeBSD.org Subject: Re: svn commit: r328996 - head/sys/kern Message-ID: <4b73bfc1-9b08-11e6-85a6-2b8e4d689a81@FreeBSD.org> In-Reply-To: <1076365a-db07-0b28-9f97-3a7cc2a73dd6@multiplay.co.uk> References: <201802072152.w17Lq0gd048728@repo.freebsd.org> <1076365a-db07-0b28-9f97-3a7cc2a73dd6@multiplay.co.uk>
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On 08/02/2018 00:41, Steven Hartland wrote: > What would be the expected behavior if this was triggered, app crash or kernel > panic...? To be honest, I haven't analyzed it much. I would expect either a crash when trying to unbusy a page that is not busy or hanging while forever waiting for a leaked page to get unbusied or hitting some KASSERT. > On 07/02/2018 21:52, Andriy Gapon wrote: >> Author: avg >> Date: Wed Feb 7 21:51:59 2018 >> New Revision: 328996 >> URL: https://svnweb.freebsd.org/changeset/base/328996 >> >> Log: >> exec_map_first_page: fix an inverse condition introduced in r254138 >> >> While the bug itself was serious, as we could either pass a non-busied >> page to vm_pager_get_pages() or leak a busy page, it could only be >> triggered under a very rare condition where the page is already inserted >> into the object, but it is not valid yet. >> >> Reviewed by: kib >> MFC after: 2 weeks >> >> Modified: >> head/sys/kern/kern_exec.c >> >> Modified: head/sys/kern/kern_exec.c >> ============================================================================== >> --- head/sys/kern/kern_exec.c Wed Feb 7 20:36:37 2018 (r328995) >> +++ head/sys/kern/kern_exec.c Wed Feb 7 21:51:59 2018 (r328996) >> @@ -1009,7 +1009,7 @@ exec_map_first_page(imgp) >> if ((ma[i] = vm_page_next(ma[i - 1])) != NULL) { >> if (ma[i]->valid) >> break; >> - if (vm_page_tryxbusy(ma[i])) >> + if (!vm_page_tryxbusy(ma[i])) >> break; >> } else { >> ma[i] = vm_page_alloc(object, i, >> > -- Andriy Gapon
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