[PATCH] rangeset: make inquiry functions tolerate NULL inputs

[PATCH] rangeset: make inquiry functions tolerate NULL inputs

[Jan Beulich]

Rather than special casing the ->iomem_caps check in x86's
get_page_from_l1e() for the dom_xen case, let's be more tolerant in
general, along the lines of rangeset_is_empty(): A never allocated
rangeset can't possibly contain or overlap any range.

Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/common/rangeset.c
+++ b/xen/common/rangeset.c
@@ -256,6 +256,9 @@ bool_t rangeset_contains_range(
 
     ASSERT(s <= e);
 
+    if ( !r )
+        return false;
+
     read_lock(&r->lock);
     x = find_range(r, s);
     contains = (x && (x->e >= e));
@@ -272,6 +275,9 @@ bool_t rangeset_overlaps_range(
 
     ASSERT(s <= e);
 
+    if ( !r )
+        return false;
+
     read_lock(&r->lock);
     x = find_range(r, e);
     overlaps = (x && (s <= x->e));




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Re: [PATCH] rangeset: make inquiry functions tolerate NULL inputs

[Roger Pau Monné]

On Fri, Aug 17, 2018 at 03:20:11AM -0600, Jan Beulich wrote:
> Rather than special casing the ->iomem_caps check in x86's
> get_page_from_l1e() for the dom_xen case, let's be more tolerant in
> general, along the lines of rangeset_is_empty(): A never allocated
> rangeset can't possibly contain or overlap any range.
> 
> Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

LGTM:

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

As said in the commit message, this is done to avoid an extra check in
get_page_from_l1e I assume, so should the extra check also be dropped
here?

Thanks, Roger.

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Re: [PATCH] rangeset: make inquiry functions tolerate NULL inputs

[Jan Beulich]

>>> On 17.08.18 at 11:29, <roger.pau@citrix.com> wrote:
> On Fri, Aug 17, 2018 at 03:20:11AM -0600, Jan Beulich wrote:
>> Rather than special casing the ->iomem_caps check in x86's
>> get_page_from_l1e() for the dom_xen case, let's be more tolerant in
>> general, along the lines of rangeset_is_empty(): A never allocated
>> rangeset can't possibly contain or overlap any range.
>> 
>> Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> 
> LGTM:
> 
> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks.

> As said in the commit message, this is done to avoid an extra check in
> get_page_from_l1e I assume, so should the extra check also be dropped
> here?

I'm afraid I don't understand: I indeed mean to avoid adding a
NULL check in get_page_from_l1e(). But what check are you thinking
of that could be dropped? Or in other words, what is "here" in
your reply?

Jan


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Re: [PATCH] rangeset: make inquiry functions tolerate NULL inputs

[Wei Liu]

On Fri, Aug 17, 2018 at 03:20:11AM -0600, Jan Beulich wrote:
> Rather than special casing the ->iomem_caps check in x86's
> get_page_from_l1e() for the dom_xen case, let's be more tolerant in
> general, along the lines of rangeset_is_empty(): A never allocated
> rangeset can't possibly contain or overlap any range.
> 
> Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Wei Liu <wei.liu2@citrix.com>

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Re: [PATCH] rangeset: make inquiry functions tolerate NULL inputs

[Roger Pau Monné]

On Fri, Aug 17, 2018 at 03:41:31AM -0600, Jan Beulich wrote:
> >>> On 17.08.18 at 11:29, <roger.pau@citrix.com> wrote:
> > As said in the commit message, this is done to avoid an extra check in
> > get_page_from_l1e I assume, so should the extra check also be dropped
> > here?
> 
> I'm afraid I don't understand: I indeed mean to avoid adding a
> NULL check in get_page_from_l1e(). But what check are you thinking
> of that could be dropped? Or in other words, what is "here" in
> your reply?

Oh, I understand now, this is to prevent adding a check, not to remove
a check that's already in the code.

'here' meant the patch, since I wrongly assumed that this was to
remove a check that was already in the code base.

Thanks, Roger.

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