-stable review patch. If anyone has any objections, please let us know. --------------------- From: Serge Hallyn upstream commit: aedb60a67c10a0861af179725d060765262ba0fb 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 Acked-by: Andrew G. Morgan Earlier-version-tested-by: Luiz Fernando N. Capitulino Acked-by: Casey Schaufler Signed-off-by: Linus Torvalds [chrisw@sous-sol.org: backport to 2.6.24.4] Signed-off-by: Chris Wright --- include/linux/security.h | 3 +-- security/capability.c | 1 - security/commoncap.c | 39 --------------------------------------- 3 files changed, 1 insertion(+), 42 deletions(-) --- a/include/linux/security.h +++ b/include/linux/security.h @@ -62,7 +62,6 @@ extern int cap_inode_need_killpriv(struc 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 (st 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) --- a/security/capability.c +++ b/security/capability.c @@ -40,7 +40,6 @@ static struct security_operations capabi .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, --- a/security/commoncap.c +++ b/security/commoncap.c @@ -527,40 +527,6 @@ int cap_task_setnice (struct task_struct 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; -} #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 { 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) -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/