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Message-ID: <20080229212634.GA7278@vino.hallyn.com>
Date: Fri, 29 Feb 2008 15:26:34 -0600
From: serge@...lyn.com
To: "Luiz Fernando N. Capitulino" <lcapitulino@...driva.com.br>
Cc: serge@...lyn.com, lkml <linux-kernel@...r.kernel.org>,
linux-security-module@...r.kernel.org,
Andrew Morgan <morgan@...nel.org>,
Stephen Smalley <sds@...ch.ncsc.mil>,
Mike Galbraith <efault@....de>, buraphalinuxserver@...il.com,
elendil@...net.nl, stable@...nel.org
Subject: Re: [PATCH 1/1] file capabilities: remove cap_task_kill()
Quoting Luiz Fernando N. Capitulino (lcapitulino@...driva.com.br):
> Em Thu, 28 Feb 2008 11:38:17 -0600
> serge@...lyn.com escreveu:
>
> | 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().
> |
> | This patch removes cap_task_kill().
>
> 2.6.24 seems to have the same bug, what about a rediff for it and
> submit the patch to -stable team?
Luiz, could you confirm that the below works?
thanks,
-serge
>From c77b7d418933c14707383f06a1da61169e84071b 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()
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().
This patch removes cap_task_kill().
Signed-off-by: Serge Hallyn <serge@...lyn.com>
---
include/linux/security.h | 3 +--
security/capability.c | 1 -
security/commoncap.c | 39 ---------------------------------------
3 files changed, 1 insertions(+), 42 deletions(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index ac05083..d842ee3 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -62,7 +62,6 @@ 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_setscheduler (struct task_struct *p, int policy, struct sched_param *lp);
extern int cap_task_setioprio (struct task_struct *p, int ioprio);
extern int cap_task_setnice (struct task_struct *p, int nice);
@@ -2112,7 +2111,7 @@ 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 9e99f36..2c6e06d 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 ea61bc7..6e9065c 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -527,40 +527,6 @@ 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)
-{
- if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info)))
- return 0;
-
- /*
- * 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->euid == 0 && p->uid == current->uid)
- return 0;
-
- /* sigcont is permitted within same session */
- if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p)))
- 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;
-}
#else
int cap_task_setscheduler (struct task_struct *p, int policy,
struct sched_param *lp)
@@ -575,11 +541,6 @@ 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
void cap_task_reparent_to_init (struct task_struct *p)
--
1.5.2.5
--
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