CRED: Neuter sys_capset()

Take away the ability for sys_capset() to affect processes other than current.

This means that current will not need to lock its own credentials when reading
them against interference by other processes.

This has effectively been the case for a while anyway, since:

 (1) Without LSM enabled, sys_capset() is disallowed.

 (2) With file-based capabilities, sys_capset() is neutered.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: Andrew G. Morgan <morgan@kernel.org>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 1 insertions, 11 deletions

diff --git a/fs/open.c b/fs/open.c
index 83cdb9d..500cc0c 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -441,17 +441,7 @@ asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode)
 	current->fsgid = current->gid;
 
 	if (!issecure(SECURE_NO_SETUID_FIXUP)) {
-		/*
-		 * Clear the capabilities if we switch to a non-root user
-		 */
-#ifndef CONFIG_SECURITY_FILE_CAPABILITIES
-		/*
-		 * FIXME: There is a race here against sys_capset.  The
-		 * capabilities can change yet we will restore the old
-		 * value below.  We should hold task_capabilities_lock,
-		 * but we cannot because user_path_at can sleep.
-		 */
-#endif /* ndef CONFIG_SECURITY_FILE_CAPABILITIES */
+		/* Clear the capabilities if we switch to a non-root user */
 		if (current->uid)
 			old_cap = cap_set_effective(__cap_empty_set);
 		else