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-   -   netlink: kill eff_cap from struct netlink_skb_parms (http://www.linux-archive.org/device-mapper-development/496574-netlink-kill-eff_cap-struct-netlink_skb_parms.html)

Patrick McHardy 03-03-2011 08:38 AM

netlink: kill eff_cap from struct netlink_skb_parms
 
commit 8ff259625f0ab295fa085b0718eed13093813fbc
Author: Patrick McHardy <kaber@trash.net>
Date: Thu Mar 3 10:17:31 2011 +0100

netlink: kill eff_cap from struct netlink_skb_parms

Netlink message processing in the kernel is synchronous these days,
capabilities can be checked directly in security_netlink_recv() from
the current process.

Signed-off-by: Patrick McHardy <kaber@trash.net>

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 8cbfaa6..fe81c85 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -2177,7 +2177,7 @@ static void drbd_connector_callback(struct cn_msg *req, struct netlink_skb_parms
return;
}

- if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN)) {
+ if (!cap_raised(current_cap(), CAP_SYS_ADMIN)) {
retcode = ERR_PERM;
goto fail;
}
diff --git a/drivers/md/dm-log-userspace-transfer.c b/drivers/md/dm-log-userspace-transfer.c
index 049eaf1..1f23e04 100644
--- a/drivers/md/dm-log-userspace-transfer.c
+++ b/drivers/md/dm-log-userspace-transfer.c
@@ -134,7 +134,7 @@ static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
{
struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);

- if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))
+ if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
return;

spin_lock(&receiving_list_lock);
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 66823b8..4c4ac3f 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -160,7 +160,6 @@ struct netlink_skb_parms {
struct ucred creds; /* Skb credentials */
__u32 pid;
__u32 dst_group;
- kernel_cap_t eff_cap;
};

#define NETLINK_CB(skb) (*(struct netlink_skb_parms*)&((skb)->cb))
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 97ecd92..a808fb1 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1364,12 +1364,6 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
NETLINK_CB(skb).dst_group = dst_group;
memcpy(NETLINK_CREDS(skb), &siocb->scm->creds, sizeof(struct ucred));

- /* What can I do? Netlink is asynchronous, so that
- we will have to save current capabilities to
- check them, when this message will be delivered
- to corresponding kernel module. --ANK (980802)
- */
-
err = -EFAULT;
if (memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len)) {
kfree_skb(skb);
diff --git a/security/commoncap.c b/security/commoncap.c
index 64c2ed9..a83e607 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -52,13 +52,12 @@ static void warn_setuid_and_fcaps_mixed(const char *fname)

int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
{
- NETLINK_CB(skb).eff_cap = current_cap();
return 0;
}

int cap_netlink_recv(struct sk_buff *skb, int cap)
{
- if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
+ if (!cap_raised(current_cap(), cap))
return -EPERM;
return 0;
}
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Chris Wright 03-03-2011 04:32 PM

netlink: kill eff_cap from struct netlink_skb_parms
 
* Patrick McHardy (kaber@trash.net) wrote:

> commit 8ff259625f0ab295fa085b0718eed13093813fbc
> Author: Patrick McHardy <kaber@trash.net>
> Date: Thu Mar 3 10:17:31 2011 +0100
>
> netlink: kill eff_cap from struct netlink_skb_parms
>
> Netlink message processing in the kernel is synchronous these days,
> capabilities can be checked directly in security_netlink_recv() from
> the current process.
>
> Signed-off-by: Patrick McHardy <kaber@trash.net>

Thanks for doing that Patrick. I looked at this earlier and thought
there was still an async path, but I guess that's just to another
userspace process.

BTW, I think you missed a couple connector based callers:

drivers/staging/pohmelfs/config.c: if (!cap_raised(nsp->eff_cap, CAP_SYS_AD
drivers/video/uvesafb.c: if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))

Fix those and:

Acked-by: Chris Wright <chrisw@sous-sol.org>

Ideally, we'd consolidate those into a variant of security_netlink_recv().
However the issue is with types. Inside connector callback we only have
netlink_skb_params (seems inapproriate to cast back out to skb).

We could change the lsm hook to only pass nsp, but SELinux actually
cares about the netlink type. Any ideas?

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David Miller 03-03-2011 05:56 PM

netlink: kill eff_cap from struct netlink_skb_parms
 
From: Chris Wright <chrisw@sous-sol.org>
Date: Thu, 3 Mar 2011 09:32:30 -0800

> * Patrick McHardy (kaber@trash.net) wrote:
>
>> commit 8ff259625f0ab295fa085b0718eed13093813fbc
>> Author: Patrick McHardy <kaber@trash.net>
>> Date: Thu Mar 3 10:17:31 2011 +0100
>>
>> netlink: kill eff_cap from struct netlink_skb_parms
>>
>> Netlink message processing in the kernel is synchronous these days,
>> capabilities can be checked directly in security_netlink_recv() from
>> the current process.
>>
>> Signed-off-by: Patrick McHardy <kaber@trash.net>
>
> Thanks for doing that Patrick. I looked at this earlier and thought
> there was still an async path, but I guess that's just to another
> userspace process.
>
> BTW, I think you missed a couple connector based callers:
>
> drivers/staging/pohmelfs/config.c: if (!cap_raised(nsp->eff_cap, CAP_SYS_AD
> drivers/video/uvesafb.c: if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))
>
> Fix those and:
>
> Acked-by: Chris Wright <chrisw@sous-sol.org>

Patrick, I'll apply your first patch, please respin this second patch with
the changes mentioned here.

Thanks!

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Chris Wright 03-03-2011 07:15 PM

netlink: kill eff_cap from struct netlink_skb_parms
 
* David Miller (davem@davemloft.net) wrote:
> From: Chris Wright <chrisw@sous-sol.org>
> Date: Thu, 3 Mar 2011 09:32:30 -0800
>
> > * Patrick McHardy (kaber@trash.net) wrote:
> >
> >> commit 8ff259625f0ab295fa085b0718eed13093813fbc
> >> Author: Patrick McHardy <kaber@trash.net>
> >> Date: Thu Mar 3 10:17:31 2011 +0100
> >>
> >> netlink: kill eff_cap from struct netlink_skb_parms
> >>
> >> Netlink message processing in the kernel is synchronous these days,
> >> capabilities can be checked directly in security_netlink_recv() from
> >> the current process.
> >>
> >> Signed-off-by: Patrick McHardy <kaber@trash.net>
> >
> > Thanks for doing that Patrick. I looked at this earlier and thought
> > there was still an async path, but I guess that's just to another
> > userspace process.
> >
> > BTW, I think you missed a couple connector based callers:
> >
> > drivers/staging/pohmelfs/config.c: if (!cap_raised(nsp->eff_cap, CAP_SYS_AD
> > drivers/video/uvesafb.c: if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))
> >
> > Fix those and:
> >
> > Acked-by: Chris Wright <chrisw@sous-sol.org>
>
> Patrick, I'll apply your first patch, please respin this second patch with
> the changes mentioned here.

Here, I respun it so I could work on top of it

thanks,
-chris
---
From: Patrick McHardy <kaber@trash.net>
Subject: [PATCH 2/2 v2] netlink: kill eff_cap from struct netlink_skb_parms

Netlink message processing in the kernel is synchronous these days,
capabilities can be checked directly in security_netlink_recv() from
the current process.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Reviewed-by: James Morris <jmorris@namei.org>
[chrisw: update to include pohmelfs and uvesafb]
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---

I did not do exhaustive .config compile tests

drivers/block/drbd/drbd_nl.c | 2 +-
drivers/md/dm-log-userspace-transfer.c | 2 +-
drivers/staging/pohmelfs/config.c | 2 +-
drivers/video/uvesafb.c | 2 +-
include/linux/netlink.h | 1 -
net/netlink/af_netlink.c | 6 ------
security/commoncap.c | 3 +--
7 files changed, 5 insertions(+), 13 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 8cbfaa6..fe81c85 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -2177,7 +2177,7 @@ static void drbd_connector_callback(struct cn_msg *req, struct netlink_skb_parms
return;
}

- if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN)) {
+ if (!cap_raised(current_cap(), CAP_SYS_ADMIN)) {
retcode = ERR_PERM;
goto fail;
}
diff --git a/drivers/md/dm-log-userspace-transfer.c b/drivers/md/dm-log-userspace-transfer.c
index 049eaf1..1f23e04 100644
--- a/drivers/md/dm-log-userspace-transfer.c
+++ b/drivers/md/dm-log-userspace-transfer.c
@@ -134,7 +134,7 @@ static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp)
{
struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1);

- if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))
+ if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
return;

spin_lock(&receiving_list_lock);
diff --git a/drivers/staging/pohmelfs/config.c b/drivers/staging/pohmelfs/config.c
index 89279ba..39413b7 100644
--- a/drivers/staging/pohmelfs/config.c
+++ b/drivers/staging/pohmelfs/config.c
@@ -525,7 +525,7 @@ static void pohmelfs_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *n
{
int err;

- if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))
+ if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
return;

switch (msg->flags) {
diff --git a/drivers/video/uvesafb.c b/drivers/video/uvesafb.c
index 52ec095..5180a21 100644
--- a/drivers/video/uvesafb.c
+++ b/drivers/video/uvesafb.c
@@ -73,7 +73,7 @@ static void uvesafb_cn_callback(struct cn_msg *msg, struct netlink_skb_parms *ns
struct uvesafb_task *utask;
struct uvesafb_ktask *task;

- if (!cap_raised(nsp->eff_cap, CAP_SYS_ADMIN))
+ if (!cap_raised(current_cap(), CAP_SYS_ADMIN))
return;

if (msg->seq >= UVESAFB_TASKS_MAX)
diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 66823b8..4c4ac3f 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -160,7 +160,6 @@ struct netlink_skb_parms {
struct ucred creds; /* Skb credentials */
__u32 pid;
__u32 dst_group;
- kernel_cap_t eff_cap;
};

#define NETLINK_CB(skb) (*(struct netlink_skb_parms*)&((skb)->cb))
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 97ecd92..a808fb1 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1364,12 +1364,6 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
NETLINK_CB(skb).dst_group = dst_group;
memcpy(NETLINK_CREDS(skb), &siocb->scm->creds, sizeof(struct ucred));

- /* What can I do? Netlink is asynchronous, so that
- we will have to save current capabilities to
- check them, when this message will be delivered
- to corresponding kernel module. --ANK (980802)
- */
-
err = -EFAULT;
if (memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len)) {
kfree_skb(skb);
diff --git a/security/commoncap.c b/security/commoncap.c
index 64c2ed9..a83e607 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -52,13 +52,12 @@ static void warn_setuid_and_fcaps_mixed(const char *fname)

int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
{
- NETLINK_CB(skb).eff_cap = current_cap();
return 0;
}

int cap_netlink_recv(struct sk_buff *skb, int cap)
{
- if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
+ if (!cap_raised(current_cap(), cap))
return -EPERM;
return 0;
}
--
1.7.1

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Chris Wright 03-03-2011 07:17 PM

netlink: kill eff_cap from struct netlink_skb_parms
 
* Chris Wright (chrisw@sous-sol.org) wrote:
> Ideally, we'd consolidate those into a variant of security_netlink_recv().
> However the issue is with types. Inside connector callback we only have
> netlink_skb_params (seems inapproriate to cast back out to skb).
>
> We could change the lsm hook to only pass nsp, but SELinux actually
> cares about the netlink type. Any ideas?

Actually I misremembered, it only cares on the send path.

We could completely drop skb from recv lsm hook, will send an RFC
momentarily with example.

thanks,
-chris

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