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Re: New Defects reported by Coverity Scan for XenProject
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 2 Apr 2025 16:19:43 +0200
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- Delivery-date: Wed, 02 Apr 2025 14:19:56 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 02.04.2025 14:56, scan-admin@xxxxxxxxxxxx wrote:
> ** CID 1645573: Null pointer dereferences (FORWARD_NULL)
>
>
> ________________________________________________________________________________________________________
> *** CID 1645573: Null pointer dereferences (FORWARD_NULL)
> /xen/arch/x86/mm/p2m.c: 346 in get_page_from_mfn_and_type()
> 340
> 341 if ( p2m_is_ram(t) )
> 342 {
> 343 if ( p2m_is_shared(t) )
> 344 d = dom_cow;
> 345
>>>> CID 1645573: Null pointer dereferences (FORWARD_NULL)
>>>> Passing null pointer "d" to "get_page", which dereferences it.
> 346 if ( get_page(page, d) )
> 347 return page;
> 348 }
I wonder how the tool concludes d is NULL. The only vague guess I could come
up with is that it checks a MEM_SHARING=n build, where dom_cow is always
NULL. Yet in such a build p2m_shared() is also always false. Should we perhaps
help it by forcing P2M_SHARED_TYPES (maybe also P2M_SHARABLE_TYPES) to 0 when
MEM_SHARING=n? We do such already for MEM_PAGING=n ...
Jan
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