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Date: Mon, 9 May 2016 04:23:47 +0000 From: Serge Hallyn <serge.hallyn@...ntu.com> To: Tyler Hicks <tyhicks@...onical.com> Cc: linux-security-module@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Serge Hallyn <serge.hallyn@...onical.com>, "David S . Miller" <davem@...emloft.net> Subject: Re: [PATCH 1/2] kernel: Add noaudit variant of ns_capable() Quoting Tyler Hicks (tyhicks@...onical.com): > When checking the current cred for a capability in a specific user > namespace, it isn't always desirable to have the LSMs audit the check. > This patch adds a noaudit variant of ns_capable() for when those > situations arise. > > The common logic between ns_capable() and the new ns_capable_noaudit() > is moved into a single, shared function to keep duplicated code to a > minimum and ease maintainability. > > Signed-off-by: Tyler Hicks <tyhicks@...onical.com> Acked-by: Serge E. Hallyn <serge.hallyn@...ntu.com> > --- > include/linux/capability.h | 5 +++++ > kernel/capability.c | 46 ++++++++++++++++++++++++++++++++++++---------- > 2 files changed, 41 insertions(+), 10 deletions(-) > > diff --git a/include/linux/capability.h b/include/linux/capability.h > index 00690ff..5f3c63d 100644 > --- a/include/linux/capability.h > +++ b/include/linux/capability.h > @@ -206,6 +206,7 @@ extern bool has_ns_capability_noaudit(struct task_struct *t, > struct user_namespace *ns, int cap); > extern bool capable(int cap); > extern bool ns_capable(struct user_namespace *ns, int cap); > +extern bool ns_capable_noaudit(struct user_namespace *ns, int cap); > #else > static inline bool has_capability(struct task_struct *t, int cap) > { > @@ -233,6 +234,10 @@ static inline bool ns_capable(struct user_namespace *ns, int cap) > { > return true; > } > +static inline bool ns_capable_noaudit(struct user_namespace *ns, int cap) > +{ > + return true; > +} > #endif /* CONFIG_MULTIUSER */ > extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap); > extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap); > diff --git a/kernel/capability.c b/kernel/capability.c > index 45432b5..00411c8 100644 > --- a/kernel/capability.c > +++ b/kernel/capability.c > @@ -361,6 +361,24 @@ bool has_capability_noaudit(struct task_struct *t, int cap) > return has_ns_capability_noaudit(t, &init_user_ns, cap); > } > > +static bool ns_capable_common(struct user_namespace *ns, int cap, bool audit) > +{ > + int capable; > + > + if (unlikely(!cap_valid(cap))) { > + pr_crit("capable() called with invalid cap=%u\n", cap); > + BUG(); > + } > + > + capable = audit ? security_capable(current_cred(), ns, cap) : > + security_capable_noaudit(current_cred(), ns, cap); > + if (capable == 0) { > + current->flags |= PF_SUPERPRIV; > + return true; > + } > + return false; > +} > + > /** > * ns_capable - Determine if the current task has a superior capability in effect > * @ns: The usernamespace we want the capability in > @@ -374,19 +392,27 @@ bool has_capability_noaudit(struct task_struct *t, int cap) > */ > bool ns_capable(struct user_namespace *ns, int cap) > { > - if (unlikely(!cap_valid(cap))) { > - pr_crit("capable() called with invalid cap=%u\n", cap); > - BUG(); > - } > - > - if (security_capable(current_cred(), ns, cap) == 0) { > - current->flags |= PF_SUPERPRIV; > - return true; > - } > - return false; > + return ns_capable_common(ns, cap, true); > } > EXPORT_SYMBOL(ns_capable); > > +/** > + * ns_capable_noaudit - Determine if the current task has a superior capability > + * (unaudited) in effect > + * @ns: The usernamespace we want the capability in > + * @cap: The capability to be tested for > + * > + * Return true if the current task has the given superior capability currently > + * available for use, false if not. > + * > + * This sets PF_SUPERPRIV on the task if the capability is available on the > + * assumption that it's about to be used. > + */ > +bool ns_capable_noaudit(struct user_namespace *ns, int cap) > +{ > + return ns_capable_common(ns, cap, false); > +} > +EXPORT_SYMBOL(ns_capable_noaudit); > > /** > * capable - Determine if the current task has a superior capability in effect > -- > 2.7.4 >
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