From a6dbb1ef2fc8d73578eacd02ac701f4233175c9f Mon Sep 17 00:00:00 2001 From: "Andrew G. Morgan" Date: Mon, 21 Jan 2008 17:18:30 -0800 Subject: [PATCH] Fix filesystem capability support In linux-2.6.24-rc1, security/commoncap.c:cap_inh_is_capped() was introduced. It has the exact reverse of its intended behavior. This led to an unintended privilege esculation involving a process' inheritable capability set. To be exposed to this bug, you need to have Filesystem Capabilities enabled and in use. That is: - CONFIG_SECURITY_FILE_CAPABILITIES must be defined for the buggy code to be compiled in. - You also need to have files on your system marked with fI bits raised. Signed-off-by: Andrew G. Morgan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- security/commoncap.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/security/commoncap.c b/security/commoncap.c index 5bc1895f3f9c..ea61bc73f6d3 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -59,6 +59,12 @@ int cap_netlink_recv(struct sk_buff *skb, int cap) EXPORT_SYMBOL(cap_netlink_recv); +/* + * NOTE WELL: cap_capable() cannot be used like the kernel's capable() + * function. That is, it has the reverse semantics: cap_capable() + * returns 0 when a task has a capability, but the kernel's capable() + * returns 1 for this case. + */ int cap_capable (struct task_struct *tsk, int cap) { /* Derived from include/linux/sched.h:capable. */ @@ -107,10 +113,11 @@ static inline int cap_block_setpcap(struct task_struct *target) static inline int cap_inh_is_capped(void) { /* - * return 1 if changes to the inheritable set are limited - * to the old permitted set. + * Return 1 if changes to the inheritable set are limited + * to the old permitted set. That is, if the current task + * does *not* possess the CAP_SETPCAP capability. */ - return !cap_capable(current, CAP_SETPCAP); + return (cap_capable(current, CAP_SETPCAP) != 0); } #else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */