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Xen/x86: don't bail early from clear_foreign_p2m_mapping()

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Its sibling (set_foreign_p2m_mapping()) as well as the sibling of its
only caller (gnttab_map_refs()) don't clean up after themselves in case
of error. Higher level callers are expected to do so. However, in order
for that to really clean up any partially set up state, the operation
should not terminate upon encountering an entry in unexpected state. It
is particularly relevant to notice here that set_foreign_p2m_mapping()
would skip setting up a p2m entry if its grant mapping failed, but it
would continue to set up further p2m entries as long as their mappings
succeeded.

Arguably down the road set_foreign_p2m_mapping() may want its page state
related WARN_ON() also converted to an error return.

This is part of XSA-361.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: stable@vger.kernel.org
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Jan Beulich 2021-02-15 08:49:34 +01:00 committed by Juergen Gross
parent f40ddce885
commit a35f2ef3b7
1 changed files with 5 additions and 7 deletions
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12
arch/x86/xen/p2m.c
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@ -750,17 +750,15 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref *unmap_ops,
unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i])); unsigned long mfn = __pfn_to_mfn(page_to_pfn(pages[i]));
unsigned long pfn = page_to_pfn(pages[i]); unsigned long pfn = page_to_pfn(pages[i]);
if (mfn == INVALID_P2M_ENTRY || !(mfn & FOREIGN_FRAME_BIT)) { if (mfn != INVALID_P2M_ENTRY && (mfn & FOREIGN_FRAME_BIT))
set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
else
ret = -EINVAL; ret = -EINVAL;
goto out;
}
set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
} }
if (kunmap_ops) if (kunmap_ops)
ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref,
kunmap_ops, count); kunmap_ops, count) ?: ret;
out:
return ret; return ret;
} }
EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping); EXPORT_SYMBOL_GPL(clear_foreign_p2m_mapping);