Smack: adds smackfs/ptrace interface

This allows to limit ptrace beyond the regular smack access rules.
It adds a smackfs/ptrace interface that allows smack to be configured
to require equal smack labels for PTRACE_MODE_ATTACH access.
See the changes in Documentation/security/Smack.txt below for details.

Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@partner.samsung.com>
Signed-off-by: Rafal Krypa <r.krypa@samsung.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/Documentation/security/Smack.txt b/Documentation/security/Smack.txt
index 7a2d30c132e3..5597917703e0 100644
--- a/Documentation/security/Smack.txt
+++ b/Documentation/security/Smack.txt
@@ -204,6 +204,16 @@ onlycap
         these capabilities are effective at for processes with any
         label. The value is set by writing the desired label to the
         file or cleared by writing "-" to the file.
+ptrace
+        This is used to define the current ptrace policy
+        0 - default: this is the policy that relies on smack access rules.
+            For the PTRACE_READ a subject needs to have a read access on
+            object. For the PTRACE_ATTACH a read-write access is required.
+        1 - exact: this is the policy that limits PTRACE_ATTACH. Attach is
+            only allowed when subject's and object's labels are equal.
+            PTRACE_READ is not affected. Can be overriden with CAP_SYS_PTRACE.
+        2 - draconian: this policy behaves like the 'exact' above with an
+            exception that it can't be overriden with CAP_SYS_PTRACE.
 revoke-subject
         Writing a Smack label here sets the access to '-' for all access
         rules with that subject label.