From: Xiao Guangrong <guangrong.xiao@gmail.com> To: Eric Blake <eblake@redhat.com>, pbonzini@redhat.com, mst@redhat.com, mtosatti@redhat.com Cc: kvm@vger.kernel.org, Xiao Guangrong <xiaoguangrong@tencent.com>, qemu-devel@nongnu.org, peterx@redhat.com, dgilbert@redhat.com, wei.w.wang@intel.com, jiang.biao2@zte.com.cn Subject: Re: [PATCH] migration: introduce decompress-error-check Date: Fri, 27 Apr 2018 11:15:37 +0800 [thread overview] Message-ID: <a14b1b5b-4f0c-c085-35b8-9539afa5091f@gmail.com> (raw) In-Reply-To: <32eaad8e-35a0-5240-37a2-4242b7890ab9@redhat.com> On 04/26/2018 10:01 PM, Eric Blake wrote: > On 04/26/2018 04:15 AM, guangrong.xiao@gmail.com wrote: >> From: Xiao Guangrong <xiaoguangrong@tencent.com> >> >> QEMU 2.13 enables strict check for compression & decompression to >> make the migration more robuster, that depends on the source to fix > > s/robuster/robust/ > Will fix, thank you for pointing it out. >> the internal design which triggers the unexpected error conditions > > 2.13 hasn't been released yet. Why do we need a knob to explicitly turn > off strict checking? Can we not instead make 2.13 automatically smart > enough to tell if the incoming stream is coming from an older qemu > (which might fail if the strict checks are enabled) vs. a newer qemu > (the sender gave us what we need to ensure the strict checks are > worthwhile)? > Really smart. How about introduce a new command, MIG_CMD_DECOMPRESS_ERR_CHECK, the destination will do strict check if got this command (i.e, new QEMU is running on the source), otherwise, turn the check off. >> >> To make it work for migrating old version QEMU to 2.13 QEMU, we >> introduce this parameter to disable the error check on the >> destination >> >> Signed-off-by: Xiao Guangrong <xiaoguangrong@tencent.com> >> --- > >> +++ b/qapi/migration.json >> @@ -455,6 +455,17 @@ >> # compression, so set the decompress-threads to the number about 1/4 >> # of compress-threads is adequate. >> # >> +# @decompress-error-check: check decompression errors. When false, the errors >> +# triggered by memory decompression are ignored. > > What are the consequences of such an error? Is it a security hole to > leave this at false, when a malicious migration stream can cause us to > misbehave by ignoring the errors? The issue fixed by strict error check is avoiding VM corruption if zlib failed to compress & decompress the memory, i.e, catch error conditions returned by zlib API. > >> +# When true, migration is aborted if the errors are >> +# detected. For the old QEMU versions (< 2.13) the >> +# internal design will cause decompression to fail >> +# so the destination should completely ignore the >> +# error conditions, i.e, make it be false if these >> +# QEMUs are going to be migrated. Since 2.13, this >> +# design is fixed, make it be true to avoid corrupting >> +# the VM silently (Since 2.13) > > Rather wordy; I'd suggest: > > @decompress-error-check: Set to true to abort the migration if > decompression errors are detected at the destination. Should be > left at false (default) for qemu older than 2.13, since only > newer qemu sends streams that do not trigger spurious > decompression errors. (Since 2.13) > Yup, much better. > But that's if we even need it (it SHOULD be possible to design something > into the migration stream so that you can detect this property > automatically instead of relying on the user to set the property). > Yes, can not agree with you more. :)
WARNING: multiple messages have this Message-ID (diff)
From: Xiao Guangrong <guangrong.xiao@gmail.com> To: Eric Blake <eblake@redhat.com>, pbonzini@redhat.com, mst@redhat.com, mtosatti@redhat.com Cc: kvm@vger.kernel.org, Xiao Guangrong <xiaoguangrong@tencent.com>, qemu-devel@nongnu.org, peterx@redhat.com, dgilbert@redhat.com, wei.w.wang@intel.com, jiang.biao2@zte.com.cn Subject: Re: [Qemu-devel] [PATCH] migration: introduce decompress-error-check Date: Fri, 27 Apr 2018 11:15:37 +0800 [thread overview] Message-ID: <a14b1b5b-4f0c-c085-35b8-9539afa5091f@gmail.com> (raw) In-Reply-To: <32eaad8e-35a0-5240-37a2-4242b7890ab9@redhat.com> On 04/26/2018 10:01 PM, Eric Blake wrote: > On 04/26/2018 04:15 AM, guangrong.xiao@gmail.com wrote: >> From: Xiao Guangrong <xiaoguangrong@tencent.com> >> >> QEMU 2.13 enables strict check for compression & decompression to >> make the migration more robuster, that depends on the source to fix > > s/robuster/robust/ > Will fix, thank you for pointing it out. >> the internal design which triggers the unexpected error conditions > > 2.13 hasn't been released yet. Why do we need a knob to explicitly turn > off strict checking? Can we not instead make 2.13 automatically smart > enough to tell if the incoming stream is coming from an older qemu > (which might fail if the strict checks are enabled) vs. a newer qemu > (the sender gave us what we need to ensure the strict checks are > worthwhile)? > Really smart. How about introduce a new command, MIG_CMD_DECOMPRESS_ERR_CHECK, the destination will do strict check if got this command (i.e, new QEMU is running on the source), otherwise, turn the check off. >> >> To make it work for migrating old version QEMU to 2.13 QEMU, we >> introduce this parameter to disable the error check on the >> destination >> >> Signed-off-by: Xiao Guangrong <xiaoguangrong@tencent.com> >> --- > >> +++ b/qapi/migration.json >> @@ -455,6 +455,17 @@ >> # compression, so set the decompress-threads to the number about 1/4 >> # of compress-threads is adequate. >> # >> +# @decompress-error-check: check decompression errors. When false, the errors >> +# triggered by memory decompression are ignored. > > What are the consequences of such an error? Is it a security hole to > leave this at false, when a malicious migration stream can cause us to > misbehave by ignoring the errors? The issue fixed by strict error check is avoiding VM corruption if zlib failed to compress & decompress the memory, i.e, catch error conditions returned by zlib API. > >> +# When true, migration is aborted if the errors are >> +# detected. For the old QEMU versions (< 2.13) the >> +# internal design will cause decompression to fail >> +# so the destination should completely ignore the >> +# error conditions, i.e, make it be false if these >> +# QEMUs are going to be migrated. Since 2.13, this >> +# design is fixed, make it be true to avoid corrupting >> +# the VM silently (Since 2.13) > > Rather wordy; I'd suggest: > > @decompress-error-check: Set to true to abort the migration if > decompression errors are detected at the destination. Should be > left at false (default) for qemu older than 2.13, since only > newer qemu sends streams that do not trigger spurious > decompression errors. (Since 2.13) > Yup, much better. > But that's if we even need it (it SHOULD be possible to design something > into the migration stream so that you can detect this property > automatically instead of relying on the user to set the property). > Yes, can not agree with you more. :)
next prev parent reply other threads:[~2018-04-27 3:15 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-04-26 9:15 [PATCH] migration: introduce decompress-error-check guangrong.xiao 2018-04-26 9:15 ` [Qemu-devel] " guangrong.xiao 2018-04-26 9:19 ` Xiao Guangrong 2018-04-26 9:19 ` [Qemu-devel] " Xiao Guangrong 2018-04-26 9:34 ` Dr. David Alan Gilbert 2018-04-26 9:34 ` [Qemu-devel] " Dr. David Alan Gilbert 2018-04-26 13:18 ` Xiao Guangrong 2018-04-26 13:18 ` [Qemu-devel] " Xiao Guangrong 2018-04-26 14:01 ` Eric Blake 2018-04-26 14:01 ` [Qemu-devel] " Eric Blake 2018-04-27 3:15 ` Xiao Guangrong [this message] 2018-04-27 3:15 ` Xiao Guangrong 2018-04-27 9:31 ` Peter Xu 2018-04-27 9:31 ` [Qemu-devel] " Peter Xu 2018-04-27 10:40 ` Xiao Guangrong 2018-04-27 10:40 ` [Qemu-devel] " Xiao Guangrong 2018-05-02 3:03 ` Peter Xu 2018-05-02 3:03 ` [Qemu-devel] " Peter Xu 2018-05-02 14:57 ` Dr. David Alan Gilbert 2018-05-02 14:57 ` [Qemu-devel] " Dr. David Alan Gilbert 2018-05-03 2:10 ` Peter Xu 2018-05-03 2:10 ` [Qemu-devel] " Peter Xu 2018-04-27 11:29 ` Dr. David Alan Gilbert 2018-04-27 11:29 ` [Qemu-devel] " Dr. David Alan Gilbert 2018-04-28 6:13 ` Xiao Guangrong 2018-04-28 6:13 ` [Qemu-devel] " Xiao Guangrong
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