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file capabilities: remove cap_task_kill()

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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 <serge@hallyn.com>
Acked-by: Andrew G. Morgan <morgan@kernel.org>
Earlier-version-tested-by: Luiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Serge Hallyn 2008-02-29 15:14:57 +00:00 • committed by Linus Torvalds
parent 457fb60583
commit aedb60a67c
4 changed files with 1 additions and 48 deletions
Download patch file Download diff file Expand all files Collapse all files

3
include/linux/security.h
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@ -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)