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authorKees Cook <keescook@chromium.org>2012-08-09 19:01:26 -0700
committerJames Morris <james.l.morris@oracle.com>2012-08-10 19:58:07 +1000
commit9d8dad742ad1c74d7e7210ee05d0b44961d5ea16 (patch)
treeb1e738bf17987552cdace2695d8b77328dc29bcf /Documentation
parentf4ba394c1b02e7fc2179fda8d3941a5b3b65efb6 (diff)
downloadlinux-linaro-stable-9d8dad742ad1c74d7e7210ee05d0b44961d5ea16.tar.gz
Yama: higher restrictions should block PTRACE_TRACEME
The higher ptrace restriction levels should be blocking even PTRACE_TRACEME requests. The comments in the LSM documentation are misleading about when the checks happen (the parent does not go through security_ptrace_access_check() on a PTRACE_TRACEME call). Signed-off-by: Kees Cook <keescook@chromium.org> Cc: stable@vger.kernel.org # 3.5.x and later Signed-off-by: James Morris <james.l.morris@oracle.com>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/security/Yama.txt14
1 files changed, 7 insertions, 7 deletions
diff --git a/Documentation/security/Yama.txt b/Documentation/security/Yama.txt
index e369de2d48cd..dd908cf64ecf 100644
--- a/Documentation/security/Yama.txt
+++ b/Documentation/security/Yama.txt
@@ -46,14 +46,13 @@ restrictions, it can call prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, ...)
so that any otherwise allowed process (even those in external pid namespaces)
may attach.
-These restrictions do not change how ptrace via PTRACE_TRACEME operates.
-
-The sysctl settings are:
+The sysctl settings (writable only with CAP_SYS_PTRACE) are:
0 - classic ptrace permissions: a process can PTRACE_ATTACH to any other
process running under the same uid, as long as it is dumpable (i.e.
did not transition uids, start privileged, or have called
- prctl(PR_SET_DUMPABLE...) already).
+ prctl(PR_SET_DUMPABLE...) already). Similarly, PTRACE_TRACEME is
+ unchanged.
1 - restricted ptrace: a process must have a predefined relationship
with the inferior it wants to call PTRACE_ATTACH on. By default,
@@ -61,12 +60,13 @@ The sysctl settings are:
classic criteria is also met. To change the relationship, an
inferior can call prctl(PR_SET_PTRACER, debugger, ...) to declare
an allowed debugger PID to call PTRACE_ATTACH on the inferior.
+ Using PTRACE_TRACEME is unchanged.
2 - admin-only attach: only processes with CAP_SYS_PTRACE may use ptrace
- with PTRACE_ATTACH.
+ with PTRACE_ATTACH, or through children calling PTRACE_TRACEME.
-3 - no attach: no processes may use ptrace with PTRACE_ATTACH. Once set,
- this sysctl cannot be changed to a lower value.
+3 - no attach: no processes may use ptrace with PTRACE_ATTACH nor via
+ PTRACE_TRACEME. Once set, this sysctl value cannot be changed.
The original children-only logic was based on the restrictions in grsecurity.