From: Eric W. Biederman ebiederm@xmission.com
[ Upstream commit a4ae32c71fe90794127b32d26d7ad795813b502e ]
An invariant of cap_bprm_set_creds is that every field in the new cred structure that cap_bprm_set_creds might set, needs to be set every time to ensure the fields does not get a stale value.
The field cap_ambient is not set every time cap_bprm_set_creds is called, which means that if there is a suid or sgid script with an interpreter that has neither the suid nor the sgid bits set the interpreter should be able to accept ambient credentials. Unfortuantely because cap_ambient is not reset to it's original value the interpreter can not accept ambient credentials.
Given that the ambient capability set is expected to be controlled by the caller, I don't think this is particularly serious. But it is definitely worth fixing so the code works correctly.
I have tested to verify my reading of the code is correct and the interpreter of a sgid can receive ambient capabilities with this change and cannot receive ambient capabilities without this change.
Cc: stable@vger.kernel.org Cc: Andy Lutomirski luto@kernel.org Fixes: 58319057b784 ("capabilities: ambient capabilities") Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com Signed-off-by: Sasha Levin sashal@kernel.org --- security/commoncap.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/security/commoncap.c b/security/commoncap.c index 48071ed7c445..b62f97d83fd8 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -494,6 +494,7 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) int ret; kuid_t root_uid;
+ new->cap_ambient = old->cap_ambient; if (WARN_ON(!cap_ambient_invariant_ok(old))) return -EPERM;