[PATCH 2/4] security: filesystem capabilities bugfix2

["Andrew G. Morgan" <morgan@xxxxxxxxxx>]

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Bugfix for strace, and CAP_SETPCAP, in the case that filesystem
capabilities are supported.
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From f4419c78fff77c4fa3cdfa6b0a78edae92ddf467 Mon Sep 17 00:00:00 2001
From: Andrew G. Morgan <morgan@xxxxxxxxxx>
Date: Wed, 25 Jun 2008 23:24:10 -0700
Subject: [PATCH] Blunt CAP_SETPCAP on strace with filesystem capability support

The filesystem capability support meaning for CAP_SETPCAP is less
powerful than the non-filesystem capability support. As such, when
filesystem capabilities are configured, we should not permit
CAP_SETPCAP to 'enhance' the current process through strace
manipulation of a child process.

Signed-off-by: Andrew G. Morgan <morgan@xxxxxxxxxx>
---
 security/commoncap.c |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/security/commoncap.c b/security/commoncap.c
index 5edabc7..a9ea921 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -103,10 +103,16 @@ static inline int cap_inh_is_capped(void)
 	return (cap_capable(current, CAP_SETPCAP) != 0);
 }
 
+static inline int cap_limit_straced_target(void) { return 1; }
+
 #else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */
 
 static inline int cap_block_setpcap(struct task_struct *t) { return 0; }
 static inline int cap_inh_is_capped(void) { return 1; }
+static inline int cap_limit_straced_target(void)
+{
+	return !capable(CAP_SETPCAP);
+}
 
 #endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
 
@@ -342,9 +348,10 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
 				bprm->e_uid = current->uid;
 				bprm->e_gid = current->gid;
 			}
-			if (!capable (CAP_SETPCAP)) {
-				new_permitted = cap_intersect (new_permitted,
-							current->cap_permitted);
+			if (cap_limit_straced_target()) {
+				new_permitted =
+					cap_intersect(new_permitted,
+						      current->cap_permitted);
 			}
 		}
 	}
-- 
1.5.3.7