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Date: Fri, 29 Feb 2008 02:14:53 +0700
From: "BuraphaLinux Server" <buraphalinuxserver@...il.com>
To: serge@...lyn.com
Cc: 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>, elendil@...net.nl
Subject: Re: [PATCH 1/1] file capabilities: remove cap_task_kill()
For 2.6.25-rc3,
Tested-By: John Gatewood Ham <buraphalinuxserver@...il.com>
This fixes the 'at' command for non-root users. Thank you.
On 2/29/08, serge@...lyn.com <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
> --
> 1.5.2.5
>
>
--
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