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Message-ID: <20080320031803.GA23254@sergelap.austin.ibm.com>
Date: Wed, 19 Mar 2008 22:18:03 -0500
From: "Serge E. Hallyn" <serue@...ibm.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: "Serge E. Hallyn" <serue@...ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
morgan@...nel.org, buraphalinuxserver@...il.com,
lcapitulino@...driva.com.br
Subject: Re: [PATCH 1/1] file capabilities: remove cap_task_kill() (-git)
Quoting Linus Torvalds (torvalds@...ux-foundation.org):
>
>
> On Wed, 19 Mar 2008, Andrew Morton wrote:
> >
> > umm,
> >
> > security/smack/smack_lsm.c: In function 'smack_task_kill':
> > security/smack/smack_lsm.c:1122: error: implicit declaration of function 'cap_task_kill'
Right, that was against
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6
which doesn't yet have smack. I should've been clear about that.
> Serge, can you resend with that fixed and the tested-by added?
>
> Linus
Following is the version against this morning's mmotm with the tested-by
added.
thanks,
-serge
>From c50b1c9f7a9e9434c8ddb50cb81e6b342638b8e0 Mon Sep 17 00:00:00 2001
From: Serge Hallyn <serge@...lyn.com>
Date: Fri, 29 Feb 2008 15:14:57 +0000
Subject: [PATCH 1/1] file capabilities: remove cap_task_kill() (-mmotm)
The original justification for cap_task_kill() was as follows:
check_kill_permission() does appropriate uid equivalence checks.
However with file capabilities it becomes possible for an
unprivileged user to execute a file with file capabilities
resulting in a more privileged task with the same uid.
However now that cap_task_kill() always returns 0 (permission
granted) when p->uid==current->uid, the whole hook is worthless,
and only likely to create more subtle problems in the corner cases
where it might still be called but return -EPERM. Those cases
are basically when uids are different but euid/suid is equivalent
as per the check in check_kill_permission().
One example of a still-broken application is 'at' for non-root users.
This patch removes cap_task_kill().
Signed-off-by: Serge Hallyn <serge@...lyn.com>
Acked-by: Andrew G. Morgan <morgan@...nel.org>
Tested-by: Luiz Fernando N. Capitulino <lcapitulino@...driva.com.br>
---
include/linux/security.h | 3 +--
security/capability.c | 1 -
security/commoncap.c | 33 ---------------------------------
security/smack/smack_lsm.c | 5 -----
4 files changed, 1 insertions(+), 41 deletions(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index 2231526..13fd76a 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -59,7 +59,6 @@ extern int cap_inode_need_killpriv(struct dentry *dentry);
extern int cap_inode_killpriv(struct dentry *dentry);
extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags);
extern void cap_task_reparent_to_init (struct task_struct *p);
-extern int cap_task_kill(struct task_struct *p, struct siginfo *info, int sig, u32 secid);
extern int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5, long *rc_p);
extern int cap_task_setscheduler (struct task_struct *p, int policy, struct sched_param *lp);
@@ -2276,7 +2275,7 @@ static inline int security_task_kill (struct task_struct *p,
struct siginfo *info, int sig,
u32 secid)
{
- return cap_task_kill(p, info, sig, secid);
+ return 0;
}
static inline int security_task_wait (struct task_struct *p)
diff --git a/security/capability.c b/security/capability.c
index 8340655..38ac54e 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -40,7 +40,6 @@ static struct security_operations capability_ops = {
.inode_need_killpriv = cap_inode_need_killpriv,
.inode_killpriv = cap_inode_killpriv,
- .task_kill = cap_task_kill,
.task_setscheduler = cap_task_setscheduler,
.task_setioprio = cap_task_setioprio,
.task_setnice = cap_task_setnice,
diff --git a/security/commoncap.c b/security/commoncap.c
index 200361d..e8c3f5e 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -537,34 +537,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
return cap_safe_nice(p);
}
-int cap_task_kill(struct task_struct *p, struct siginfo *info,
- int sig, u32 secid)
-{
- /*
- * Running a setuid root program raises your capabilities.
- * Killing your own setuid root processes was previously
- * allowed.
- * We must preserve legacy signal behavior in this case.
- */
- if (p->uid == current->uid)
- return 0;
-
- if (secid)
- /*
- * Signal sent as a particular user.
- * Capabilities are ignored. May be wrong, but it's the
- * only thing we can do at the moment.
- * Used only by usb drivers?
- */
- return 0;
- if (cap_issubset(p->cap_permitted, current->cap_permitted))
- return 0;
- if (capable(CAP_KILL))
- return 0;
-
- return -EPERM;
-}
-
/*
* called from kernel/sys.c for prctl(PR_CABSET_DROP)
* done without task_capability_lock() because it introduces
@@ -596,11 +568,6 @@ int cap_task_setnice (struct task_struct *p, int nice)
{
return 0;
}
-int cap_task_kill(struct task_struct *p, struct siginfo *info,
- int sig, u32 secid)
-{
- return 0;
-}
#endif
int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 4365fad..2a5eb83 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -1117,11 +1117,6 @@ static int smack_task_movememory(struct task_struct *p)
static int smack_task_kill(struct task_struct *p, struct siginfo *info,
int sig, u32 secid)
{
- int rc;
-
- rc = cap_task_kill(p, info, sig, secid);
- if (rc != 0)
- return rc;
/*
* Sending a signal requires that the sender
* can write the receiver.
--
1.5.2.5
--
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