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[PATCH 1/6] kexec: fix a memory leak in crash_shrink_memory()

Zhen Lei posted 6 patches 2 years, 8 months ago
[PATCH 1/6] kexec: fix a memory leak in crash_shrink_memory()
Posted by Zhen Lei 2 years, 8 months ago 
If the value of parameter 'new_size' is in the semi-open and semi-closed
interval (crashk_res.end - KEXEC_CRASH_MEM_ALIGN + 1, crashk_res.end], the
calculation result of ram_res is:
	ram_res->start = crashk_res.end + 1
	ram_res->end   = crashk_res.end
The operation of function insert_resource() fails, and ram_res is not
added to iomem_resource. As a result, the memory of the control block
ram_res is leaked.

In fact, on all architectures, the start address and size of crashk_res
are already aligned by KEXEC_CRASH_MEM_ALIGN. Therefore, we do not need to
round up crashk_res.start again. Instead, we should round up 'new_size'
in advance.

Fixes: 6480e5a09237 ("kdump: add missing RAM resource in crash_shrink_memory()")
Fixes: 06a7f711246b ("kexec: premit reduction of the reserved memory size")
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 kernel/kexec_core.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 3d578c6fefee385..22acee18195a591 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1122,6 +1122,7 @@ int crash_shrink_memory(unsigned long new_size)
 	start = crashk_res.start;
 	end = crashk_res.end;
 	old_size = (end == 0) ? 0 : end - start + 1;
+	new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
 	if (new_size >= old_size) {
 		ret = (new_size == old_size) ? 0 : -EINVAL;
 		goto unlock;
@@ -1133,9 +1134,7 @@ int crash_shrink_memory(unsigned long new_size)
 		goto unlock;
 	}
 
-	start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
-	end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
-
+	end = start + new_size;
 	crash_free_reserved_phys_range(end, crashk_res.end);
 
 	if ((start == end) && (crashk_res.parent != NULL))
-- 
2.25.1
Re: [PATCH 1/6] kexec: fix a memory leak in crash_shrink_memory()
Posted by Baoquan He 2 years, 8 months ago 
On 05/27/23 at 08:34pm, Zhen Lei wrote:
> If the value of parameter 'new_size' is in the semi-open and semi-closed
> interval (crashk_res.end - KEXEC_CRASH_MEM_ALIGN + 1, crashk_res.end], the
> calculation result of ram_res is:
> 	ram_res->start = crashk_res.end + 1
> 	ram_res->end   = crashk_res.end

If the new_size is smaller than KEXEC_CRASH_MEM_ALIGN, does it make
any sense except of testing purpose? Do we need to fail this kind of
shrinking, or just shrink all the left crash memory?

> The operation of function insert_resource() fails, and ram_res is not
> added to iomem_resource. As a result, the memory of the control block
> ram_res is leaked.
> 
> In fact, on all architectures, the start address and size of crashk_res
> are already aligned by KEXEC_CRASH_MEM_ALIGN. Therefore, we do not need to
> round up crashk_res.start again. Instead, we should round up 'new_size'
> in advance.
> 
> Fixes: 6480e5a09237 ("kdump: add missing RAM resource in crash_shrink_memory()")
> Fixes: 06a7f711246b ("kexec: premit reduction of the reserved memory size")
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
>  kernel/kexec_core.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index 3d578c6fefee385..22acee18195a591 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -1122,6 +1122,7 @@ int crash_shrink_memory(unsigned long new_size)
>  	start = crashk_res.start;
>  	end = crashk_res.end;
>  	old_size = (end == 0) ? 0 : end - start + 1;
> +	new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
>  	if (new_size >= old_size) {
>  		ret = (new_size == old_size) ? 0 : -EINVAL;
>  		goto unlock;
> @@ -1133,9 +1134,7 @@ int crash_shrink_memory(unsigned long new_size)
>  		goto unlock;
>  	}
>  
> -	start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
> -	end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
> -
> +	end = start + new_size;
>  	crash_free_reserved_phys_range(end, crashk_res.end);
>  
>  	if ((start == end) && (crashk_res.parent != NULL))
> -- 
> 2.25.1
>
Re: [PATCH 1/6] kexec: fix a memory leak in crash_shrink_memory()
Posted by Leizhen (ThunderTown) 2 years, 8 months ago 

On 2023/5/31 8:13, Baoquan He wrote:
> On 05/27/23 at 08:34pm, Zhen Lei wrote:
>> If the value of parameter 'new_size' is in the semi-open and semi-closed
>> interval (crashk_res.end - KEXEC_CRASH_MEM_ALIGN + 1, crashk_res.end], the
>> calculation result of ram_res is:
>> 	ram_res->start = crashk_res.end + 1
>> 	ram_res->end   = crashk_res.end
> 
> If the new_size is smaller than KEXEC_CRASH_MEM_ALIGN, does it make
> any sense except of testing purpose? Do we need to fail this kind of
> shrinking, or just shrink all the left crash memory?

We can't give a fixed value, that is, how much crash memory is reserved to
ensure that the capture kernel runs. The size of KEXEC_CRASH_MEM_ALIGN is
only one page on non-s390 platforms. So, it's better to keep the code simple,
and let the user(administrator) shrink the crash memory reasonably.

include/linux/kexec.h
#define KEXEC_CRASH_MEM_ALIGN	PAGE_SIZE

> 
>> The operation of function insert_resource() fails, and ram_res is not
>> added to iomem_resource. As a result, the memory of the control block
>> ram_res is leaked.
>>
>> In fact, on all architectures, the start address and size of crashk_res
>> are already aligned by KEXEC_CRASH_MEM_ALIGN. Therefore, we do not need to
>> round up crashk_res.start again. Instead, we should round up 'new_size'
>> in advance.
>>
>> Fixes: 6480e5a09237 ("kdump: add missing RAM resource in crash_shrink_memory()")
>> Fixes: 06a7f711246b ("kexec: premit reduction of the reserved memory size")
>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>> ---
>>  kernel/kexec_core.c | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
>> index 3d578c6fefee385..22acee18195a591 100644
>> --- a/kernel/kexec_core.c
>> +++ b/kernel/kexec_core.c
>> @@ -1122,6 +1122,7 @@ int crash_shrink_memory(unsigned long new_size)
>>  	start = crashk_res.start;
>>  	end = crashk_res.end;
>>  	old_size = (end == 0) ? 0 : end - start + 1;
>> +	new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
>>  	if (new_size >= old_size) {
>>  		ret = (new_size == old_size) ? 0 : -EINVAL;
>>  		goto unlock;
>> @@ -1133,9 +1134,7 @@ int crash_shrink_memory(unsigned long new_size)
>>  		goto unlock;
>>  	}
>>  
>> -	start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
>> -	end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
>> -
>> +	end = start + new_size;
>>  	crash_free_reserved_phys_range(end, crashk_res.end);
>>  
>>  	if ((start == end) && (crashk_res.parent != NULL))
>> -- 
>> 2.25.1
>>
> 
> .
> 

-- 
Regards,
  Zhen Lei
Re: [PATCH 1/6] kexec: fix a memory leak in crash_shrink_memory()
Posted by Baoquan He 2 years, 8 months ago 
On 05/31/23 at 09:16am, Leizhen (ThunderTown) wrote:
> 
> 
> On 2023/5/31 8:13, Baoquan He wrote:
> > On 05/27/23 at 08:34pm, Zhen Lei wrote:
> >> If the value of parameter 'new_size' is in the semi-open and semi-closed
> >> interval (crashk_res.end - KEXEC_CRASH_MEM_ALIGN + 1, crashk_res.end], the
> >> calculation result of ram_res is:
> >> 	ram_res->start = crashk_res.end + 1
> >> 	ram_res->end   = crashk_res.end
> > 
> > If the new_size is smaller than KEXEC_CRASH_MEM_ALIGN, does it make
> > any sense except of testing purpose? Do we need to fail this kind of
> > shrinking, or just shrink all the left crash memory?

OK, I misread your log. You are saying the new_size is close to
crashk_res.end but has a tiny difference in your example, I
thought the new_size is smaller than KEXEC_CRASH_MEM_ALIGN which is just
in the opposite direction.

Yea, it does have the possibility to waste a ram_res but does nothing
even though the chance is very small.

Acked-by: Baoquan He <bhe@redhat.com>

> 
> We can't give a fixed value, that is, how much crash memory is reserved to
> ensure that the capture kernel runs. The size of KEXEC_CRASH_MEM_ALIGN is
> only one page on non-s390 platforms. So, it's better to keep the code simple,
> and let the user(administrator) shrink the crash memory reasonably.
> 
> include/linux/kexec.h
> #define KEXEC_CRASH_MEM_ALIGN	PAGE_SIZE

> 
> > 
> >> The operation of function insert_resource() fails, and ram_res is not
> >> added to iomem_resource. As a result, the memory of the control block
> >> ram_res is leaked.
> >>
> >> In fact, on all architectures, the start address and size of crashk_res
> >> are already aligned by KEXEC_CRASH_MEM_ALIGN. Therefore, we do not need to
> >> round up crashk_res.start again. Instead, we should round up 'new_size'
> >> in advance.
> >>
> >> Fixes: 6480e5a09237 ("kdump: add missing RAM resource in crash_shrink_memory()")
> >> Fixes: 06a7f711246b ("kexec: premit reduction of the reserved memory size")
> >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> >> ---
> >>  kernel/kexec_core.c | 5 ++---
> >>  1 file changed, 2 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> >> index 3d578c6fefee385..22acee18195a591 100644
> >> --- a/kernel/kexec_core.c
> >> +++ b/kernel/kexec_core.c
> >> @@ -1122,6 +1122,7 @@ int crash_shrink_memory(unsigned long new_size)
> >>  	start = crashk_res.start;
> >>  	end = crashk_res.end;
> >>  	old_size = (end == 0) ? 0 : end - start + 1;
> >> +	new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
> >>  	if (new_size >= old_size) {
> >>  		ret = (new_size == old_size) ? 0 : -EINVAL;
> >>  		goto unlock;
> >> @@ -1133,9 +1134,7 @@ int crash_shrink_memory(unsigned long new_size)
> >>  		goto unlock;
> >>  	}
> >>  
> >> -	start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
> >> -	end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
> >> -
> >> +	end = start + new_size;
> >>  	crash_free_reserved_phys_range(end, crashk_res.end);
> >>  
> >>  	if ((start == end) && (crashk_res.parent != NULL))
> >> -- 
> >> 2.25.1
> >>
> > 
> > .
> > 
> 
> -- 
> Regards,
>   Zhen Lei
>

Patchew 2.1-devel-b67e4c2

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