1. Patchew
  2. QEMU
  3. View series

[PATCH-for-6.1 v2] softmmu/physmem: fix wrong assertion in qemu_ram_alloc_internal()

David Hildenbrand posted 1 patch 2 years, 9 months ago
Test checkpatch passed
Patches applied successfully (tree, apply log)
git fetch https://github.com/patchew-project/qemu tags/patchew/20210805092350.31195-1-david@redhat.com
softmmu/physmem.c | 1 -
1 file changed, 1 deletion(-)
[PATCH-for-6.1 v2] softmmu/physmem: fix wrong assertion in qemu_ram_alloc_internal()
Posted by David Hildenbrand 2 years, 9 months ago 
When adding RAM_NORESERVE, we forgot to remove the old assertion when
adding the updated one, most probably when reworking the patches or
rebasing. We can easily crash QEMU by adding
  -object memory-backend-ram,id=mem0,size=500G,reserve=off
to the QEMU cmdline:
  qemu-system-x86_64: ../softmmu/physmem.c:2146: qemu_ram_alloc_internal:
  Assertion `(ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC))
  == 0' failed.

Fix it by removing the old assertion.

Fixes: 8dbe22c6868b ("memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()")
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---

v1 -> v2:
- Added rbs
- Tagged for 6.1 inclusion

---
 softmmu/physmem.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 3c1912a1a0..2e18947598 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -2143,7 +2143,6 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
     RAMBlock *new_block;
     Error *local_err = NULL;
 
-    assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) == 0);
     assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
                           RAM_NORESERVE)) == 0);
     assert(!host ^ (ram_flags & RAM_PREALLOC));
-- 
2.31.1
Re: [PATCH-for-6.1 v2] softmmu/physmem: fix wrong assertion in qemu_ram_alloc_internal()
Posted by Pankaj Gupta 2 years, 9 months ago 
> When adding RAM_NORESERVE, we forgot to remove the old assertion when
> adding the updated one, most probably when reworking the patches or
> rebasing. We can easily crash QEMU by adding
>   -object memory-backend-ram,id=mem0,size=500G,reserve=off
> to the QEMU cmdline:
>   qemu-system-x86_64: ../softmmu/physmem.c:2146: qemu_ram_alloc_internal:
>   Assertion `(ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC))
>   == 0' failed.
>
> Fix it by removing the old assertion.
>
> Fixes: 8dbe22c6868b ("memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()")
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>
> v1 -> v2:
> - Added rbs
> - Tagged for 6.1 inclusion
>
> ---
>  softmmu/physmem.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> index 3c1912a1a0..2e18947598 100644
> --- a/softmmu/physmem.c
> +++ b/softmmu/physmem.c
> @@ -2143,7 +2143,6 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
>      RAMBlock *new_block;
>      Error *local_err = NULL;
>
> -    assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) == 0);
>      assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
>                            RAM_NORESERVE)) == 0);
>      assert(!host ^ (ram_flags & RAM_PREALLOC));
> --
> 2.31.1

Reviewed-by: Pankaj Gupta <pankaj.gupta@ionos.com>

>
>
Re: [PATCH-for-6.1 v2] softmmu/physmem: fix wrong assertion in qemu_ram_alloc_internal()
Posted by Peter Xu 2 years, 9 months ago 
On Thu, Aug 05, 2021 at 11:23:50AM +0200, David Hildenbrand wrote:
> When adding RAM_NORESERVE, we forgot to remove the old assertion when
> adding the updated one, most probably when reworking the patches or
> rebasing. We can easily crash QEMU by adding
>   -object memory-backend-ram,id=mem0,size=500G,reserve=off
> to the QEMU cmdline:
>   qemu-system-x86_64: ../softmmu/physmem.c:2146: qemu_ram_alloc_internal:
>   Assertion `(ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC))
>   == 0' failed.
> 
> Fix it by removing the old assertion.
> 
> Fixes: 8dbe22c6868b ("memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()")
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> 
> v1 -> v2:
> - Added rbs
> - Tagged for 6.1 inclusion
> 
> ---
>  softmmu/physmem.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> index 3c1912a1a0..2e18947598 100644
> --- a/softmmu/physmem.c
> +++ b/softmmu/physmem.c
> @@ -2143,7 +2143,6 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
>      RAMBlock *new_block;
>      Error *local_err = NULL;
>  
> -    assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) == 0);
>      assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
>                            RAM_NORESERVE)) == 0);
>      assert(!host ^ (ram_flags & RAM_PREALLOC));
> -- 
> 2.31.1
> 

Today I just noticed this patch is still missing for 6.1. How many users are
there with reserve=off?  Would it be worth rc4 or not?

-- 
Peter Xu
Re: [PATCH-for-6.1 v2] softmmu/physmem: fix wrong assertion in qemu_ram_alloc_internal()
Posted by David Hildenbrand 2 years, 9 months ago 
On 16.08.21 22:52, Peter Xu wrote:
> On Thu, Aug 05, 2021 at 11:23:50AM +0200, David Hildenbrand wrote:
>> When adding RAM_NORESERVE, we forgot to remove the old assertion when
>> adding the updated one, most probably when reworking the patches or
>> rebasing. We can easily crash QEMU by adding
>>    -object memory-backend-ram,id=mem0,size=500G,reserve=off
>> to the QEMU cmdline:
>>    qemu-system-x86_64: ../softmmu/physmem.c:2146: qemu_ram_alloc_internal:
>>    Assertion `(ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC))
>>    == 0' failed.
>>
>> Fix it by removing the old assertion.
>>
>> Fixes: 8dbe22c6868b ("memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()")
>> Reviewed-by: Peter Xu <peterx@redhat.com>
>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Peter Xu <peterx@redhat.com>
>> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
>> Signed-off-by: David Hildenbrand <david@redhat.com>
>> ---
>>
>> v1 -> v2:
>> - Added rbs
>> - Tagged for 6.1 inclusion
>>
>> ---
>>   softmmu/physmem.c | 1 -
>>   1 file changed, 1 deletion(-)
>>
>> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
>> index 3c1912a1a0..2e18947598 100644
>> --- a/softmmu/physmem.c
>> +++ b/softmmu/physmem.c
>> @@ -2143,7 +2143,6 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
>>       RAMBlock *new_block;
>>       Error *local_err = NULL;
>>   
>> -    assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) == 0);
>>       assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
>>                             RAM_NORESERVE)) == 0);
>>       assert(!host ^ (ram_flags & RAM_PREALLOC));
>> -- 
>> 2.31.1
>>
> 
> Today I just noticed this patch is still missing for 6.1. How many users are
> there with reserve=off?  Would it be worth rc4 or not?
> 

Indeed, I forgot to follow up, thanks for bringing this up.

Libvirt does not support virtio-mem yet and consequently doesn't support 
reserve=off yet. (there are use cases without virtio-mem, but I don't 
think anybody is using it yet)

It's an easy way to crash QEMU, but we could also fix in the -stable 
tree instead.

(most probably you and me should also be doing PULL requests for "Memory 
API", we'll have to discuss with Paolo)

-- 
Thanks,

David / dhildenb
Re: [PATCH-for-6.1 v2] softmmu/physmem: fix wrong assertion in qemu_ram_alloc_internal()
Posted by Peter Xu 2 years, 9 months ago 
On Tue, Aug 17, 2021 at 09:14:32AM +0200, David Hildenbrand wrote:
> Libvirt does not support virtio-mem yet and consequently doesn't support
> reserve=off yet. (there are use cases without virtio-mem, but I don't think
> anybody is using it yet)
> 
> It's an easy way to crash QEMU, but we could also fix in the -stable tree
> instead.

I hit this when trying with some extreme bitmap tests then I remembered this
patch, but that shouldn't really be used by any real customer for sure.

Sounds good then, thanks.

-- 
Peter Xu
Re: [PATCH-for-6.1 v2] softmmu/physmem: fix wrong assertion in qemu_ram_alloc_internal()
Posted by Peter Maydell 2 years, 9 months ago 
On Tue, 17 Aug 2021 at 08:14, David Hildenbrand <david@redhat.com> wrote:
>
> On 16.08.21 22:52, Peter Xu wrote:
> > On Thu, Aug 05, 2021 at 11:23:50AM +0200, David Hildenbrand wrote:
> >> When adding RAM_NORESERVE, we forgot to remove the old assertion when
> >> adding the updated one, most probably when reworking the patches or
> >> rebasing. We can easily crash QEMU by adding
> >>    -object memory-backend-ram,id=mem0,size=500G,reserve=off
> >> to the QEMU cmdline:
> >>    qemu-system-x86_64: ../softmmu/physmem.c:2146: qemu_ram_alloc_internal:
> >>    Assertion `(ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC))
> >>    == 0' failed.
> >>
> >> Fix it by removing the old assertion.
> >>
> >> Fixes: 8dbe22c6868b ("memory: Introduce RAM_NORESERVE and wire it up in qemu_ram_mmap()")
> >> Reviewed-by: Peter Xu <peterx@redhat.com>
> >> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> >> Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> >> Cc: Paolo Bonzini <pbonzini@redhat.com>
> >> Cc: Peter Xu <peterx@redhat.com>
> >> Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
> >> Signed-off-by: David Hildenbrand <david@redhat.com>
> >> ---
> >>
> >> v1 -> v2:
> >> - Added rbs
> >> - Tagged for 6.1 inclusion
> >>
> >> ---
> >>   softmmu/physmem.c | 1 -
> >>   1 file changed, 1 deletion(-)
> >>
> >> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> >> index 3c1912a1a0..2e18947598 100644
> >> --- a/softmmu/physmem.c
> >> +++ b/softmmu/physmem.c
> >> @@ -2143,7 +2143,6 @@ RAMBlock *qemu_ram_alloc_internal(ram_addr_t size, ram_addr_t max_size,
> >>       RAMBlock *new_block;
> >>       Error *local_err = NULL;
> >>
> >> -    assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC)) == 0);
> >>       assert((ram_flags & ~(RAM_SHARED | RAM_RESIZEABLE | RAM_PREALLOC |
> >>                             RAM_NORESERVE)) == 0);
> >>       assert(!host ^ (ram_flags & RAM_PREALLOC));
> >> --
> >> 2.31.1
> >>
> >
> > Today I just noticed this patch is still missing for 6.1. How many users are
> > there with reserve=off?  Would it be worth rc4 or not?
> >
>
> Indeed, I forgot to follow up, thanks for bringing this up.
>
> Libvirt does not support virtio-mem yet and consequently doesn't support
> reserve=off yet. (there are use cases without virtio-mem, but I don't
> think anybody is using it yet)
>
> It's an easy way to crash QEMU, but we could also fix in the -stable
> tree instead.

It is a really obvious right fix, though, so I'm going to apply
it for rc4 anyway.

thanks
-- PMM

Patchew 2.1-devel-0870f84

© 2016 - 2024 Red Hat, Inc.