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>
This commit is contained in:
Andrew G. Morgan 2008-01-21 17:18:30 -08:00 committed by Linus Torvalds
parent a10336043b
commit a6dbb1ef2f
1 changed files with 10 additions and 3 deletions

View File

@ -59,6 +59,12 @@ int cap_netlink_recv(struct sk_buff *skb, int cap)
EXPORT_SYMBOL(cap_netlink_recv); 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) int cap_capable (struct task_struct *tsk, int cap)
{ {
/* Derived from include/linux/sched.h:capable. */ /* 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) static inline int cap_inh_is_capped(void)
{ {
/* /*
* return 1 if changes to the inheritable set are limited * Return 1 if changes to the inheritable set are limited
* to the old permitted set. * 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 */ #else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */