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Date: Sat, 01 Mar 2008 14:05:07 -0800
From: "Andrew G. Morgan" <morgan@...nel.org>
To: serge@...lyn.com
CC: lkml <linux-kernel@...r.kernel.org>,
linux-security-module@...r.kernel.org,
Stephen Smalley <sds@...ch.ncsc.mil>,
Mike Galbraith <efault@....de>, buraphalinuxserver@...il.com,
elendil@...net.nl
Subject: Re: [PATCH 1/1] file capabilities: remove cap_task_kill()
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Hash: SHA1
Acked-by: Andrew G. Morgan <morgan@...nel.org>
Cheers
Andrew
serge@...lyn.com wrote:
| 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 | 40
- ----------------------------------------
| security/smack/smack_lsm.c | 5 -----
| 4 files changed, 1 insertions(+), 48 deletions(-)
|
| diff --git a/include/linux/security.h b/include/linux/security.h
| index fe52cde..95cb830 100644
| --- a/include/linux/security.h
| +++ b/include/linux/security.h
| @@ -63,7 +63,6 @@ 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);
| @@ -2138,7 +2137,7 @@ 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 bb0c095..06d5c94 100644
| --- a/security/commoncap.c
| +++ b/security/commoncap.c
| @@ -540,41 +540,6 @@ 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->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;
| -}
| -
| /*
| * called from kernel/sys.c for prctl(PR_CABSET_DROP)
| * done without task_capability_lock() because it introduces
| @@ -605,11 +570,6 @@ 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)
| diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
| index 770eb06..a9ca412 100644
| --- a/security/smack/smack_lsm.c
| +++ b/security/smack/smack_lsm.c
| @@ -1124,11 +1124,6 @@ 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;
| /*
| * Special cases where signals really ought to go through
| * in spite of policy. Stephen Smalley suggests it may
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