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  • patch Re: kvm crash in 5.14.1?

    From Francois Le Hir@21:1/5 to All on Mon Oct 11 00:10:02 2021
    Greetings,

    I am not sure what is the correct process and I apologize if this is not the appropriate way to do it, but could you please include this patch in your next testing, unstable or experimental kernel ? 

    Re: kvm crash in 5.14.1? — Linux Kernel

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    Re: kvm crash in 5.14.1? — Linux Kernel

    Linux Kernel: Re: kvm crash in 5.14.1?
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    same thread but the actual patch is in this message: Re: kvm crash in 5.14.1? — Linux Kernel

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    Re: kvm crash in 5.14.1? — Linux Kernel

    Linux Kernel: Re: kvm crash in 5.14.1?
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    Thanks,Regards,
    Francois Le Hir



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    OfficeDocumentSettings></xml><![endif]--></head><body><div class="yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div dir="ltr" data-setdir="false">Greetings,<br></div><div dir="ltr" data-setdir="false">
    <br></div><div dir="ltr" data-setdir="false">I am not sure what is the correct process and I apologize if this is not the appropriate way to do it, but could you please include this patch in your next testing, unstable or experimental kernel ?&nbsp; <br><
    /div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false"><a href="https://www.spinics.net/lists/kernel/msg4105122.html" rel="nofollow" target="_blank" class="enhancr_card_4214829881">Re: kvm crash in 5.14.1? — Linux Kernel</
    </div><div><br></div><div id="ydpaae8e7beenhancr_card_4214829881" class="ydpaae8e7beyahoo-link-enhancr-card ydpaae8e7beyahoo-link-enhancr-not-allow-cover ydpaae8e7beymail-preserve-class ydpaae8e7beymail-preserve-style" style="max-width: 400px; font-
    family: YahooSans, &quot;Helvetica Neue&quot;, &quot;Segoe UI&quot;, Helvetica, Arial, sans-serif; position: relative;" data-url="https://www.spinics.net/lists/kernel/msg4105122.html" data-type="YENHANCER" data-size="MEDIUM" contenteditable="false"><a
    href="https://www.spinics.net/lists/kernel/msg4105122.html" style="text-decoration-line: none !important; text-decoration-style: solid !important; text-decoration-color: currentcolor !important; color: rgb(0, 0, 0) !important;" class="ydpaae8e7beyahoo-
    enhancr-cardlink" rel="nofollow" target="_blank"><table class="ydpaae8e7becard-wrapper ydpaae8e7beyahoo-ignore-table" style="max-width:400px" cellspacing="0" cellpadding="0" border="0"><tbody><tr><td width="400"><table class="ydpaae8e7becard
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    align:middle;padding:12px 24px 16px 12px;width:99%;font-family:YahooSans, &quot;Helvetica Neue&quot;, &quot;Segoe UI&quot;, Helvetica, Arial, sans-serif;border-radius:0 0 2px 0"><h2 class="ydpaae8e7becard-title" style="font-size: 14px; line-height: 19px;
    margin: 0px 0px 6px; font-family: YahooSans, &quot;Helvetica Neue&quot;, &quot;Segoe UI&quot;, Helvetica, Arial, sans-serif; color: rgb(38, 40, 42); max-width: 314px;">Re: kvm crash in 5.14.1? — Linux Kernel</h2><p class="ydpaae8e7becard-description"
    style="font-size: 12px; line-height: 16px; margin: 0px; color: rgb(151, 155, 167);">Linux Kernel: Re: kvm crash in 5.14.1?</p></td></tr></tbody></table></td></tr></tbody></table></td></tr></tbody></table></a><div class="loadingSpinnerContainer" style="
    position: absolute; top: 0px; width: 100%; height: 100%; display: flex; align-items: center; justify-content: center; background-color: rgba(255, 255, 255, 0.3);"><div class="D_F F_n gl_C ab_C H_6MGW o_h"><div class="W_6MGW H_6MGW D_X ah_1PEzoz" data-
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    path><path class="cdPFi_n cZ13pKbK_Z2aVTcY cZ1XO2Ji_dRA c2abBOT_EY cZ1vNhDV_rd cZV8aCd_pI ah_14s73" d="M12,2c5.523,0,10,4.477,10,10s-4.477,10-10,10"></path></svg></div></div></div></div><div><br></div><div dir="ltr" data-setdir="false">same thread but
    the actual patch is in this message: <a href="https://www.spinics.net/lists/kernel/msg4097233.html" rel="nofollow" target="_blank" class="enhancr_card_4156917948">Re: kvm crash in 5.14.1? — Linux Kernel</a></div><div><br></div><div id="
    ydpc3c530c1enhancr_card_4156917948" class="ydpc3c530c1yahoo-link-enhancr-card ydpc3c530c1yahoo-link-enhancr-not-allow-cover ydpc3c530c1ymail-preserve-class ydpc3c530c1ymail-preserve-style" style="max-width:400px;font-family:YahooSans, &quot;Helvetica
    Neue&quot;, &quot;Segoe UI&quot;, Helvetica, Arial, sans-serif" data-url="https://www.spinics.net/lists/kernel/msg4097233.html" data-type="YENHANCER" data-size="MEDIUM" contenteditable="false"><a href="https://www.spinics.net/lists/kernel/msg4097233.html"
    style="text-decoration-line: none !important; text-decoration-style: solid !important; text-decoration-color: currentcolor !important; color: rgb(0, 0, 0) !important;" class="ydpc3c530c1yahoo-enhancr-cardlink" rel="nofollow" target="_blank"><table class=
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    background-repeat: repeat; background-attachment: scroll; background-image: none; background-size: auto; position: relative; z-index: 2; width: 100%; max-width: 400px; border-radius: 0px 0px 2px 2px; border-top: 1px solid rgb(224, 228, 233);" cellspacing=
    "0" cellpadding="0" border="0"><tbody><tr><td style="background-color:#ffffff;padding:16px 0 16px 12px;vertical-align:top;border-radius:0 0 0 2px"></td><td style="vertical-align:middle;padding:12px 24px 16px 12px;width:99%;font-family:YahooSans, &quot;
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    Segoe UI&quot;, Helvetica, Arial, sans-serif; color: rgb(38, 40, 42); max-width: 314px;">Re: kvm crash in 5.14.1? — Linux Kernel</h2><p class="ydpc3c530c1card-description" style="font-size: 12px; line-height: 16px; margin: 0px; color: rgb(151, 155, 167)
    ;">Linux Kernel: Re: kvm crash in 5.14.1?</p></td></tr></tbody></table></td></tr></tbody></table></td></tr></tbody></table></a></div><div><br></div><div><br></div><div dir="ltr" data-setdir="false">Thanks,</div><div dir="ltr" data-setdir="false">Regards,<
    /div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">Francois Le Hir<br></div><div><br></div><div><br></div></div></body></html>

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  • From Diederik de Haas@21:1/5 to All on Mon Oct 11 15:38:08 2021
    Copy: flehir@yahoo.com (Francois Le Hir)

    Hi,

    On Sunday, 10 October 2021 23:42:39 CEST Francois Le Hir wrote:
    I am not sure what is the correct process and I apologize if this is not the appropriate way to do it, but could you please include this patch in your next testing, unstable or experimental kernel ?

    Please don't use HTML email, but plain-text email. It is (strongly) preferred and in several cases (like linux MLs) even required.

    Re: kvm crash in 5.14.1? — Linux Kernel


    Re: kvm crash in 5.14.1? — Linux Kernel

    Linux Kernel: Re: kvm crash in 5.14.1?

    The plain-text view of your mail doesn't show what this issue is about; with plain-text email that wouldn't be the case ;-)

    For reference, this is what the issue is about:
    I haven't reproduced the crash, but the code signature (CMP against an absolute address) is quite distinct, and is consistent across all three crashes. I'm pretty sure the issue is that page_is_secretmem() doesn't
    check for a null page->mapping, e.g. if the page is truncated, which IIUC
    can happen in parallel since gup() doesn't hold the lock.

    I think this should fix the problems?

    diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
    index 21c3771e6a56..988528b5da43 100644
    --- a/include/linux/secretmem.h
    +++ b/include/linux/secretmem.h
    @@ -23,7 +23,7 @@ static inline bool page_is_secretmem(struct page *page)

    mapping = (struct address_space *)

    ((unsigned long)page->mapping & ~PAGE_MAPPING_FLAGS);

    - if (mapping != page->mapping)
    + if (!mapping || mapping != page->mapping)

    return false;

    return mapping->a_ops == &secretmem_aops;

    src: https://www.spinics.net/lists/kernel/msg4094132.html

    This file was introduced in (tag) v5.14-rc1 and apparently causes a problem with KVM. I don't use KVM so I haven't experienced this issue myself.

    The best way to report an issue in the Debian kernel, is to file a bug in Debian's BTS with the 'reportbug' tool against the package you encountered the bug in. Provide all the relevant information in it. And in this case also a reference to LKML for the upstream discussion.

    To get the fix in Debian's kernel, the general procedure is to get the fix included in the upstream Linux kernel first. Both current 'master' and 'linux-5.14.y' branches do currently not contain that fix, so do/help to get that done first. When it's accepted upstream, it'll likely get backported to linux-5.14.y and then it would get picked up automatically when the Debian kernel upgrades to that version.
    In some cases it could get backported/applied to Debian before that, but the general requirement is that it is *first* applied upstream.

    HTH,
    Diederik
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