Re: [Cocci] Incorrect match with when != condition

[Denis Efremov]

On 3/17/21 11:32 PM, Julia Lawall wrote:



On Wed, 17 Mar 2021, Denis Efremov wrote:


Hi,

I'm trying to write the check to detect the absence of commit
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=51b2ee7d006a736a9126e8111d1f24e4fd0afaa6
in kernel. The pattern can be:

@err exists@
identifier namlen, dchild, dparent, exp;
position p;
statement S;
@@

compose_entry_fh(..., int namlen, ...)
{
...
if (namlen == 2) {
*   dchild =@p dget_parent(dparent);
... when != dparent == exp->ex_path.dentry


add when forall here.  There does exist a path that does not contain the
dparent == exp->ex_path.dentry test.  That is the path that takesthe first
goto out.


This solved the problem, thanks!
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Re: [Cocci] Incorrect match with when != condition

[Julia Lawall]

On Wed, 17 Mar 2021, Denis Efremov wrote:

> Hi,
>
> I'm trying to write the check to detect the absence of commit
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=51b2ee7d006a736a9126e8111d1f24e4fd0afaa6
> in kernel. The pattern can be:
>
> @err exists@
> identifier namlen, dchild, dparent, exp;
> position p;
> statement S;
> @@
>
> compose_entry_fh(..., int namlen, ...)
> {
>   ...
>   if (namlen == 2) {
> * dchild =@p dget_parent(dparent);
>   ... when != dparent == exp->ex_path.dentry

add when forall here.  There does exist a path that does not contain the
dparent == exp->ex_path.dentry test.  That is the path that takesthe first
goto out.

julia

>   } else S
>   ...
> }
>
> But unfortunately, it matches even the fixed source. I think
> that condition "... when != dparent == exp->ex_path.dentry" doesn't
> work as expected. Steps to reproduce:
>
> $ cd linux # latest master branch
> $ wget
> https://raw.githubusercontent.com/evdenis/cvehound/b2d109c959c299dce10274c1806406fc5653e5d0/cvehound/cve/CVE-2021-3178.cocci
> $ spatch -D detect --cocci-file CVE-2021-3178.cocci fs/nfsd/nfs3xdr.c
> fs/nfsd/nfs3xdr.c:935:10-11: ERROR: CVE-2021-3178
> diff =
> --- fs/nfsd/nfs3xdr.c
> +++ /tmp/cocci-output-526900-b87df1-nfs3xdr.c
> @@ -932,7 +932,6 @@ compose_entry_fh(struct nfsd3_readdirres
>  if (isdotent(name, namlen)) {
> if (namlen == 2) {
>   // !!! shouldn't match because of if (dparent ==
> exp->ex_path.dentry) goto out; check after
> -   dchild = dget_parent(dparent);
> /*
>  * Don't return filehandle for ".." if we're at
>  * the filesystem or export root:
> $ spatch --version
> spatch version 1.1.0 compiled with OCaml version 4.11.1
>
> Thanks,
> Denis
>
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[Cocci] Incorrect match with when != condition

[Denis Efremov]

Hi,

I'm trying to write the check to detect the absence of commit
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=51b2ee7d006a736a9126e8111d1f24e4fd0afaa6
in kernel. The pattern can be:

@err exists@
identifier namlen, dchild, dparent, exp;
position p;
statement S;
@@

compose_entry_fh(..., int namlen, ...)
{
...
if (namlen == 2) {
*   dchild =@p dget_parent(dparent);
... when != dparent == exp->ex_path.dentry
} else S
...
}

But unfortunately, it matches even the fixed source. I think
that condition "... when != dparent == exp->ex_path.dentry" doesn't
work as expected. Steps to reproduce:

$ cd linux # latest master branch
$ wget 
https://raw.githubusercontent.com/evdenis/cvehound/b2d109c959c299dce10274c1806406fc5653e5d0/cvehound/cve/CVE-2021-3178.cocci
$ spatch -D detect --cocci-file CVE-2021-3178.cocci fs/nfsd/nfs3xdr.c
fs/nfsd/nfs3xdr.c:935:10-11: ERROR: CVE-2021-3178
diff =
--- fs/nfsd/nfs3xdr.c
+++ /tmp/cocci-output-526900-b87df1-nfs3xdr.c
@@ -932,7 +932,6 @@ compose_entry_fh(struct nfsd3_readdirres
 
if (isdotent(name, namlen)) {

if (namlen == 2) {
// !!! shouldn't match because of if (dparent == 
exp->ex_path.dentry) goto out; check after
-   dchild = dget_parent(dparent);
/*
 * Don't return filehandle for ".." if we're at
 * the filesystem or export root:
$ spatch --version
spatch version 1.1.0 compiled with OCaml version 4.11.1

Thanks,
Denis
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