From a6dbb1ef2fc8d73578eacd02ac701f4233175c9f Mon Sep 17 00:00:00 2001
From: "Andrew G. Morgan" <morgan@kernel.org>
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 <morgan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@akpm@linux-foundation.org>
---
security/commoncap.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/security/commoncap.c b/security/commoncap.c
index 5bc1895f3f9ce0..ea61bc73f6d3c4 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 */
--
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