From aedb60a67c10a0861af179725d060765262ba0fb Mon Sep 17 00:00:00 2001 From: Serge Hallyn Date: Fri, 29 Feb 2008 15:14:57 +0000 Subject: [PATCH] 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(). 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 --- include/linux/security.h | 3 +-- security/capability.c | 1 - security/commoncap.c | 40 -------------------------------------- security/smack/smack_lsm.c | 5 ----- 4 files changed, 1 insertion(+), 48 deletions(-) diff --git a/include/linux/security.h b/include/linux/security.h index b07357ca21..c673dfd4df 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -57,7 +57,6 @@ 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); @@ -2187,7 +2186,7 @@ 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 9e99f36a8b..2c6e06d18f 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 bb0c095f57..06d5c9469b 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 38d707593b..732ba27923 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -1117,11 +1117,6 @@ 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 -- 2.39.5