Messages in this thread Patch in this message | | | Date | Fri, 29 Feb 2008 15:26:34 -0600 | From | serge@hallyn ... | Subject | Re: [PATCH 1/1] file capabilities: remove cap_task_kill() |
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Quoting Luiz Fernando N. Capitulino (lcapitulino@mandriva.com.br): > Em Thu, 28 Feb 2008 11:38:17 -0600 > serge@hallyn.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@hallyn.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@hallyn.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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