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Message-Id: <20200608231211.3363633-321-sashal@kernel.org>
Date: Mon, 8 Jun 2020 19:07:26 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>,
Andy Lutomirski <luto@...nel.org>,
Sasha Levin <sashal@...nel.org>,
linux-security-module@...r.kernel.org
Subject: [PATCH AUTOSEL 5.6 321/606] exec: Always set cap_ambient in cap_bprm_set_creds
From: "Eric W. Biederman" <ebiederm@...ssion.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@...r.kernel.org
Cc: Andy Lutomirski <luto@...nel.org>
Fixes: 58319057b784 ("capabilities: ambient capabilities")
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
security/commoncap.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/security/commoncap.c b/security/commoncap.c
index f4ee0ae106b2..0ca31c8bc0b1 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -812,6 +812,7 @@ 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;
--
2.25.1
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