security: filesystem capabilities: fix fragile setuid fixup code

This commit includes a bugfix for the fragile setuid fixup code in the
case that filesystem capabilities are supported (in access()).  The effect
of this fix is gated on filesystem capability support because changing
securebits is only supported when filesystem capabilities support is
configured.)

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/kernel/capability.c b/kernel/capability.c
index cfbe44299488..901e0fdc3fff 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -121,6 +121,27 @@ static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
  * uninteresting and/or not to be changed.
  */
 
+/*
+ * Atomically modify the effective capabilities returning the original
+ * value. No permission check is performed here - it is assumed that the
+ * caller is permitted to set the desired effective capabilities.
+ */
+kernel_cap_t cap_set_effective(const kernel_cap_t pE_new)
+{
+	kernel_cap_t pE_old;
+
+	spin_lock(&task_capability_lock);
+
+	pE_old = current->cap_effective;
+	current->cap_effective = pE_new;
+
+	spin_unlock(&task_capability_lock);
+
+	return pE_old;
+}
+
+EXPORT_SYMBOL(cap_set_effective);
+
 /**
  * sys_capget - get the capabilities of a given process.
  * @header: pointer to struct that contains capability version and