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Re: [libvirt] [PATCH 09/10] qemuDomainAttachDeviceMknod: Deal with symlinks



On 02/07/2017 11:57 AM, Martin Kletzander wrote:
> On Fri, Jan 20, 2017 at 10:42:49AM +0100, Michal Privoznik wrote:
>> Similarly to one of the previous commits, we need to deal
>> properly with symlinks in hotplug case too.
>>
>> Signed-off-by: Michal Privoznik <mprivozn redhat com>
>> ---
>> src/qemu/qemu_domain.c | 120
>> ++++++++++++++++++++++++++++++++++++++-----------
>> 1 file changed, 94 insertions(+), 26 deletions(-)
>>
> 
> ACK to this, but ...
> 
>> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
>> index 448583313..bcfb2446f 100644
>> --- a/src/qemu/qemu_domain.c
>> +++ b/src/qemu/qemu_domain.c
>> @@ -7701,17 +7763,22 @@ qemuDomainAttachDeviceMknod(virQEMUDriverPtr
>> driver,
>>     }
>> #endif
>>
>> -    if (virSecurityManagerPreFork(driver->securityManager) < 0)
>> -        goto cleanup;
>> +    if (STRPREFIX(file, DEVPREFIX)) {
>> +        if (virSecurityManagerPreFork(driver->securityManager) < 0)
>> +            goto cleanup;
>>
>> -    if (virProcessRunInMountNamespace(vm->pid,
>> -                                      qemuDomainAttachDeviceMknodHelper,
>> -                                      &data) < 0) {
>> +        if (virProcessRunInMountNamespace(vm->pid,
>> +                                         
>> qemuDomainAttachDeviceMknodHelper,
>> +                                          &data) < 0) {
> 
> ... I'm sure you have patches for this somewhere that are not posted or
> something =D However now we actually fork for every level of the
> symlink.  Even when everyone is scared of every single fork().  Can't we
> use transactions for this as well?  If not, could we enhance them so
> that we can use them?

Transactions are security driver specific. But we can imitate them here
too. Instead of direct fork() we would have a list to which we append
all the symlinks we want to create and then fork() once and execute the
list. Good point. I will work on that.

Michal


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