* [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl
@ 2016-05-06 23:04 Tyler Hicks
2016-05-06 23:04 ` [PATCH 1/2] kernel: Add noaudit variant of ns_capable() Tyler Hicks
` (2 more replies)
0 siblings, 3 replies; 9+ messages in thread
From: Tyler Hicks @ 2016-05-06 23:04 UTC (permalink / raw)
To: linux-security-module, netdev, linux-kernel
Cc: Serge Hallyn, David S . Miller
This pair of patches does away with what I believe is a useless denial
audit message when a privileged process initially accesses a net sysctl.
The bug was first discovered when running Go applications under AppArmor
confinement. It can be triggered like so:
$ echo "profile test { file, }" | sudo apparmor_parser -rq
Once the profile is loaded, invoke Go as root under confinement:
$ sudo aa-exec -p test -- go version
go version go1.6.1 linux/amd64
Here's the denial:
audit: type=1400 audit(1462575436.832:29): apparmor="DENIED" operation="capable" profile="test" pid=1157 comm="go" capability=12 capname="net_admin"
The reproducer in minimal form is:
$ sudo aa-exec -p test -- cat /proc/sys/net/core/somaxconn
128
The denial:
audit: type=1400 audit(1462575670.000:29): apparmor="DENIED" operation="capable" profile="test" pid=1161 comm="cat" capability=12 capname="net_admin"
Thanks!
Tyler
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 1/2] kernel: Add noaudit variant of ns_capable()
2016-05-06 23:04 [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl Tyler Hicks
@ 2016-05-06 23:04 ` Tyler Hicks
2016-05-09 4:23 ` Serge Hallyn
2016-05-06 23:04 ` [PATCH 2/2] net: Use ns_capable_noaudit() when determining net sysctl permissions Tyler Hicks
2016-05-09 3:56 ` [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl David Miller
2 siblings, 1 reply; 9+ messages in thread
From: Tyler Hicks @ 2016-05-06 23:04 UTC (permalink / raw)
To: linux-security-module, netdev, linux-kernel
Cc: Serge Hallyn, David S . Miller
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@canonical.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
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 2/2] net: Use ns_capable_noaudit() when determining net sysctl permissions
2016-05-06 23:04 [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl Tyler Hicks
2016-05-06 23:04 ` [PATCH 1/2] kernel: Add noaudit variant of ns_capable() Tyler Hicks
@ 2016-05-06 23:04 ` Tyler Hicks
2016-05-09 4:24 ` Serge Hallyn
2016-05-09 3:56 ` [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl David Miller
2 siblings, 1 reply; 9+ messages in thread
From: Tyler Hicks @ 2016-05-06 23:04 UTC (permalink / raw)
To: linux-security-module, netdev, linux-kernel
Cc: Serge Hallyn, David S . Miller
The capability check should not be audited since it is only being used
to determine the inode permissions. A failed check does not indicate a
violation of security policy but, when an LSM is enabled, a denial audit
message was being generated.
The denial audit message caused confusion for some application authors
because root-running Go applications always triggered the denial. To
prevent this confusion, the capability check in net_ctl_permissions() is
switched to the noaudit variant.
BugLink: https://launchpad.net/bugs/1465724
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
---
net/sysctl_net.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/sysctl_net.c b/net/sysctl_net.c
index ed98c1f..46a71c7 100644
--- a/net/sysctl_net.c
+++ b/net/sysctl_net.c
@@ -46,7 +46,7 @@ static int net_ctl_permissions(struct ctl_table_header *head,
kgid_t root_gid = make_kgid(net->user_ns, 0);
/* Allow network administrator to have same access as root. */
- if (ns_capable(net->user_ns, CAP_NET_ADMIN) ||
+ if (ns_capable_noaudit(net->user_ns, CAP_NET_ADMIN) ||
uid_eq(root_uid, current_euid())) {
int mode = (table->mode >> 6) & 7;
return (mode << 6) | (mode << 3) | mode;
--
2.7.4
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl
2016-05-06 23:04 [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl Tyler Hicks
2016-05-06 23:04 ` [PATCH 1/2] kernel: Add noaudit variant of ns_capable() Tyler Hicks
2016-05-06 23:04 ` [PATCH 2/2] net: Use ns_capable_noaudit() when determining net sysctl permissions Tyler Hicks
@ 2016-05-09 3:56 ` David Miller
2016-05-17 14:13 ` Tyler Hicks
2 siblings, 1 reply; 9+ messages in thread
From: David Miller @ 2016-05-09 3:56 UTC (permalink / raw)
To: tyhicks; +Cc: linux-security-module, netdev, linux-kernel, serge.hallyn
From: Tyler Hicks <tyhicks@canonical.com>
Date: Fri, 6 May 2016 18:04:12 -0500
> This pair of patches does away with what I believe is a useless denial
> audit message when a privileged process initially accesses a net sysctl.
The LSM folks can apply this if they agree with you.
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 1/2] kernel: Add noaudit variant of ns_capable()
2016-05-06 23:04 ` [PATCH 1/2] kernel: Add noaudit variant of ns_capable() Tyler Hicks
@ 2016-05-09 4:23 ` Serge Hallyn
0 siblings, 0 replies; 9+ messages in thread
From: Serge Hallyn @ 2016-05-09 4:23 UTC (permalink / raw)
To: Tyler Hicks
Cc: linux-security-module, netdev, linux-kernel, Serge Hallyn,
David S . Miller
Quoting Tyler Hicks (tyhicks@canonical.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@canonical.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.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
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 2/2] net: Use ns_capable_noaudit() when determining net sysctl permissions
2016-05-06 23:04 ` [PATCH 2/2] net: Use ns_capable_noaudit() when determining net sysctl permissions Tyler Hicks
@ 2016-05-09 4:24 ` Serge Hallyn
0 siblings, 0 replies; 9+ messages in thread
From: Serge Hallyn @ 2016-05-09 4:24 UTC (permalink / raw)
To: Tyler Hicks
Cc: linux-security-module, netdev, linux-kernel, Serge Hallyn,
David S . Miller
Quoting Tyler Hicks (tyhicks@canonical.com):
> The capability check should not be audited since it is only being used
> to determine the inode permissions. A failed check does not indicate a
> violation of security policy but, when an LSM is enabled, a denial audit
> message was being generated.
>
> The denial audit message caused confusion for some application authors
> because root-running Go applications always triggered the denial. To
> prevent this confusion, the capability check in net_ctl_permissions() is
> switched to the noaudit variant.
>
> BugLink: https://launchpad.net/bugs/1465724
>
> Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
> ---
> net/sysctl_net.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/sysctl_net.c b/net/sysctl_net.c
> index ed98c1f..46a71c7 100644
> --- a/net/sysctl_net.c
> +++ b/net/sysctl_net.c
> @@ -46,7 +46,7 @@ static int net_ctl_permissions(struct ctl_table_header *head,
> kgid_t root_gid = make_kgid(net->user_ns, 0);
>
> /* Allow network administrator to have same access as root. */
> - if (ns_capable(net->user_ns, CAP_NET_ADMIN) ||
> + if (ns_capable_noaudit(net->user_ns, CAP_NET_ADMIN) ||
> uid_eq(root_uid, current_euid())) {
> int mode = (table->mode >> 6) & 7;
> return (mode << 6) | (mode << 3) | mode;
> --
> 2.7.4
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl
2016-05-09 3:56 ` [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl David Miller
@ 2016-05-17 14:13 ` Tyler Hicks
2016-06-02 16:30 ` Tyler Hicks
0 siblings, 1 reply; 9+ messages in thread
From: Tyler Hicks @ 2016-05-17 14:13 UTC (permalink / raw)
To: jmorris
Cc: David Miller, linux-security-module, netdev, linux-kernel,
serge.hallyn
[-- Attachment #1.1: Type: text/plain, Size: 427 bytes --]
On 05/08/2016 10:56 PM, David Miller wrote:
> From: Tyler Hicks <tyhicks@canonical.com>
> Date: Fri, 6 May 2016 18:04:12 -0500
>
>> This pair of patches does away with what I believe is a useless denial
>> audit message when a privileged process initially accesses a net sysctl.
>
> The LSM folks can apply this if they agree with you.
Hi James - Could you pick up these two bug fix patches? Thanks!
Tyler
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 819 bytes --]
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl
2016-05-17 14:13 ` Tyler Hicks
@ 2016-06-02 16:30 ` Tyler Hicks
2016-06-03 1:00 ` James Morris
0 siblings, 1 reply; 9+ messages in thread
From: Tyler Hicks @ 2016-06-02 16:30 UTC (permalink / raw)
To: jmorris
Cc: David Miller, linux-security-module, netdev, linux-kernel,
serge.hallyn
[-- Attachment #1.1: Type: text/plain, Size: 579 bytes --]
On 05/17/2016 09:13 AM, Tyler Hicks wrote:
> On 05/08/2016 10:56 PM, David Miller wrote:
>> From: Tyler Hicks <tyhicks@canonical.com>
>> Date: Fri, 6 May 2016 18:04:12 -0500
>>
>>> This pair of patches does away with what I believe is a useless denial
>>> audit message when a privileged process initially accesses a net sysctl.
>>
>> The LSM folks can apply this if they agree with you.
>
> Hi James - Could you pick up these two bug fix patches? Thanks!
Hello - Just checking in again to see if you plan on taking these
through the security tree?
Tyler
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 819 bytes --]
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl
2016-06-02 16:30 ` Tyler Hicks
@ 2016-06-03 1:00 ` James Morris
0 siblings, 0 replies; 9+ messages in thread
From: James Morris @ 2016-06-03 1:00 UTC (permalink / raw)
To: Tyler Hicks
Cc: David Miller, linux-security-module, netdev, linux-kernel,
serge.hallyn
On Thu, 2 Jun 2016, Tyler Hicks wrote:
> On 05/17/2016 09:13 AM, Tyler Hicks wrote:
> > On 05/08/2016 10:56 PM, David Miller wrote:
> >> From: Tyler Hicks <tyhicks@canonical.com>
> >> Date: Fri, 6 May 2016 18:04:12 -0500
> >>
> >>> This pair of patches does away with what I believe is a useless denial
> >>> audit message when a privileged process initially accesses a net sysctl.
> >>
> >> The LSM folks can apply this if they agree with you.
> >
> > Hi James - Could you pick up these two bug fix patches? Thanks!
>
> Hello - Just checking in again to see if you plan on taking these
> through the security tree?
Sure, please resend.
--
James Morris
<jmorris@namei.org>
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2016-06-03 1:00 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2016-05-06 23:04 [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl Tyler Hicks
2016-05-06 23:04 ` [PATCH 1/2] kernel: Add noaudit variant of ns_capable() Tyler Hicks
2016-05-09 4:23 ` Serge Hallyn
2016-05-06 23:04 ` [PATCH 2/2] net: Use ns_capable_noaudit() when determining net sysctl permissions Tyler Hicks
2016-05-09 4:24 ` Serge Hallyn
2016-05-09 3:56 ` [PATCH 0/2] Quiet noisy LSM denial when accessing net sysctl David Miller
2016-05-17 14:13 ` Tyler Hicks
2016-06-02 16:30 ` Tyler Hicks
2016-06-03 1:00 ` James Morris
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