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SubjectRe: [PATCH] capabilities: Ambient capability set V2
On Sun, 1 Mar 2015, Serge E. Hallyn wrote:

> > +++ linux/security/commoncap.c 2015-02-26 16:10:02.347913397 -0600
> > @@ -347,15 +347,17 @@ static inline int bprm_caps_from_vfs_cap
> > *has_cap = true;
> >
> > CAP_FOR_EACH_U32(i) {
> > + __u32 ambient = current_cred()->cap_ambient.cap[i];
> > __u32 permitted = caps->permitted.cap[i];
> > __u32 inheritable = caps->inheritable.cap[i];
> >
> > /*
> > - * pP' = (X & fP) | (pI & fI)
> > + * pP' = (X & fP) | (pI & (fI | pA))
> > */
> > new->cap_permitted.cap[i] =
> > (new->cap_bset.cap[i] & permitted) |
> > - (new->cap_inheritable.cap[i] & inheritable);
> > + (new->cap_inheritable.cap[i] &
> > + (inheritable | ambient));
>
> So I'd say drop this change ^

Then the ambient caps get ignored for a executables that have capabilities
seton the file? I think we need to keep this one.

> > @@ -453,8 +455,18 @@ static int get_file_caps(struct linux_bi
> > if (rc == -EINVAL)
> > printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
> > __func__, rc, bprm->filename);
> > - else if (rc == -ENODATA)
> > + else if (rc == -ENODATA) {
> > rc = 0;
> > + if (!cap_isclear(current_cred()->cap_ambient)) {
> > + /*
> > + * The ambient caps are permitted for
> > + * files that have no caps
> > + */
> > + bprm->cred->cap_permitted =
> > + current_cred()->cap_ambient;
>
> and here set vcaps inheritable to current_cred()->ambient.

We do not call bprm_caps_from_vfs_cap() for files that have no caps so
this would have no effect. But we could set cap_inheritable here?

Fixup patch:



Subject: ambient_caps: Set inheritable bits too

We were not setting the inheritable bits as they ought to be set.

Signed-off-by: Christoph Lameter <cl@linux.com>

Index: linux/security/commoncap.c
===================================================================
--- linux.orig/security/commoncap.c 2015-03-05 09:22:32.123047869 -0600
+++ linux/security/commoncap.c 2015-03-05 09:22:32.119048001 -0600
@@ -461,6 +461,8 @@ static int get_file_caps(struct linux_bi
*/
bprm->cred->cap_permitted =
current_cred()->cap_ambient;
+ bprm->cred->cap_inheritable =
+ current_cred()->cap_ambient;
*effective = true;
}
}


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