Re: [Cocci] [PATCH v3 2/3] coccinelle: api: extend memdup_user rule with vmemdup_user()

Re: [Cocci] [PATCH v3 2/3] coccinelle: api: extend memdup_user rule with vmemdup_user()

[Julia Lawall]

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On Tue, 21 Jul 2020, Markus Elfring wrote:

> …
> > +++ b/scripts/coccinelle/api/memdup_user.cocci
> > @@ -39,6 +39,28 @@ …
> …
> > +@depends on patch@
> > +expression from,to,size;
> > +identifier l1,l2;
> > +@@
> > +
> > +-  to = \(kvmalloc\|kvzalloc\)(size,\(GFP_KERNEL\|GFP_USER\));
> > ++  to = vmemdup_user(from,size);
>
> I propose to combine the desired adjustment with the previous SmPL rule
> by using another disjunction.
>
>
> > +@rv depends on !patch@
> > +expression from,to,size;
> > +position p;
> > +statement S1,S2;
> > +@@
> > +
> > +*  to = \(kvmalloc@p\|kvzalloc@p\)(size,\(GFP_KERNEL\|GFP_USER\));
> > +   if (to==NULL || ...) S1
> > +   if (copy_from_user(to, from, size) != 0)
> > +   S2
>
> * Can it be helpful to omit the SmPL asterisk functionality from
>   the operation modes “org” and “report”?
>
> * Should the operation mode “context” work without an extra position metavariable?

This is fine as is in all three aspects.

julia

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Re: [Cocci] [PATCH v3 2/3] coccinelle: api: extend memdup_user rule with vmemdup_user()

[Julia Lawall]

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On Wed, 22 Jul 2020, Markus Elfring wrote:

> >>> +@depends on patch@
> >>> +expression from,to,size;
> >>> +identifier l1,l2;
> >>> +@@
> >>> +
> >>> +-  to = \(kvmalloc\|kvzalloc\)(size,\(GFP_KERNEL\|GFP_USER\));
> >>> ++  to = vmemdup_user(from,size);
> >>
> >> I propose to combine the desired adjustment with the previous SmPL rule
> >> by using another disjunction.
>
> How do you think about to check run time characteristics for
> the following SmPL script sketches?
>
> A)
> @R1@
> @@
> // Change something
>
> @R2@
> @@
> // Change another thing
>
>
> B)
> @Replacement_with_disjunction@
> @@
> (
> // R1: Change something
> |
> // R2: Change another thing
> )

Markus, you are welcome to try this since you are concerned about it.
But it doesn't matter.

julia

>
>
> >>> +@rv depends on !patch@
> >>> +expression from,to,size;
> >>> +position p;
> >>> +statement S1,S2;
> >>> +@@
> >>> +
> >>> +*  to = \(kvmalloc@p\|kvzalloc@p\)(size,\(GFP_KERNEL\|GFP_USER\));
> >>> +   if (to==NULL || ...) S1
> >>> +   if (copy_from_user(to, from, size) != 0)
> >>> +   S2
> >>
> >> * Can it be helpful to omit the SmPL asterisk functionality from
> >>   the operation modes “org” and “report”?
> >>
> >> * Should the operation mode “context” work without an extra position metavariable?
> >
> > This is fine as is in all three aspects.
>
> Is every technique from the Coccinelle software required for
> each operation mode in such data processing approaches?
>
> Regards,
> Markus
>

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Re: [Cocci] [v3 2/3] coccinelle: api: extend memdup_user rule with vmemdup_user()

[Julia Lawall]

On Wed, 22 Jul 2020, Markus Elfring wrote:

> > Markus, you are welcome to try this since you are concerned about it.
>
> I dare to point software design variations for some reasons.
>
>
> > But it doesn't matter.
>
> Under which circumstances would you begin to care more for involved differences
> in corresponding run time characteristics?

When the difference is hours vs seconds.  In this case, there are
tradeoffs between the two options, andI don't know which would be faster,
but I think it is extremely unlikely that the difference is noticible.
But if you are concerned about it, you are welcome to try.

julia
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[Cocci] [PATCH v3 2/3] coccinelle: api: extend memdup_user rule with vmemdup_user()

[Denis Efremov]

Add vmemdup_user() transformations to the memdup_user.cocci rule.
Commit 50fd2f298bef ("new primitive: vmemdup_user()") introduced
vmemdup_user(). The function uses kvmalloc with GPF_USER flag.

Signed-off-by: Denis Efremov <efremov@linux.com>
---
 scripts/coccinelle/api/memdup_user.cocci | 45 ++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/scripts/coccinelle/api/memdup_user.cocci b/scripts/coccinelle/api/memdup_user.cocci
index 0e29d41ecab8..60027e21c5e6 100644
--- a/scripts/coccinelle/api/memdup_user.cocci
+++ b/scripts/coccinelle/api/memdup_user.cocci
@@ -39,6 +39,28 @@ identifier l1,l2;
 -    ...+>
 -  }
 
+@depends on patch@
+expression from,to,size;
+identifier l1,l2;
+@@
+
+-  to = \(kvmalloc\|kvzalloc\)(size,\(GFP_KERNEL\|GFP_USER\));
++  to = vmemdup_user(from,size);
+   if (
+-      to==NULL
++      IS_ERR(to)
+                 || ...) {
+   <+... when != goto l1;
+-  -ENOMEM
++  PTR_ERR(to)
+   ...+>
+   }
+-  if (copy_from_user(to, from, size) != 0) {
+-    <+... when != goto l2;
+-    -EFAULT
+-    ...+>
+-  }
+
 @r depends on !patch@
 expression from,to,size;
 position p;
@@ -52,6 +74,17 @@ statement S1,S2;
    if (copy_from_user(to, from, size) != 0)
    S2
 
+@rv depends on !patch@
+expression from,to,size;
+position p;
+statement S1,S2;
+@@
+
+*  to = \(kvmalloc@p\|kvzalloc@p\)(size,\(GFP_KERNEL\|GFP_USER\));
+   if (to==NULL || ...) S1
+   if (copy_from_user(to, from, size) != 0)
+   S2
+
 @script:python depends on org@
 p << r.p;
 @@
@@ -63,3 +96,15 @@ p << r.p;
 @@
 
 coccilib.report.print_report(p[0], "WARNING opportunity for memdup_user")
+
+@script:python depends on org@
+p << rv.p;
+@@
+
+coccilib.org.print_todo(p[0], "WARNING opportunity for vmemdup_user")
+
+@script:python depends on report@
+p << rv.p;
+@@
+
+coccilib.report.print_report(p[0], "WARNING opportunity for vmemdup_user")
-- 
2.26.2

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