X-Git-Url: http://git.cascardo.eti.br/?a=blobdiff_plain;f=kernel%2Fptrace.c;h=2341efe7fe026f496095c4a9c1526a69cad3849a;hb=af7acc3df7b1cad3956579c63a70a7b85b69161b;hp=b760bae64cf123b16863b6180a68a099abca51d1;hpb=c09c9dd2e9c732658c744a802101d5c34fedde22;p=cascardo%2Flinux.git

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index b760bae64cf1..2341efe7fe02 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -219,6 +219,14 @@ static int ptrace_has_cap(struct user_namespace *ns, unsigned int mode)
 static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 {
 	const struct cred *cred = current_cred(), *tcred;
+	int dumpable = 0;
+	kuid_t caller_uid;
+	kgid_t caller_gid;
+
+	if (!(mode & PTRACE_MODE_FSCREDS) == !(mode & PTRACE_MODE_REALCREDS)) {
+		WARN(1, "denying ptrace access check without PTRACE_MODE_*CREDS\n");
+		return -EPERM;
+	}
 
 	/* May we inspect the given task?
 	 * This check is used both for attaching with ptrace
@@ -228,18 +236,33 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode)
 	 * because setting up the necessary parent/child relationship
 	 * or halting the specified task is impossible.
 	 */
-	int dumpable = 0;
+
 	/* Don't let security modules deny introspection */
 	if (same_thread_group(task, current))
 		return 0;
 	rcu_read_lock();
+	if (mode & PTRACE_MODE_FSCREDS) {
+		caller_uid = cred->fsuid;
+		caller_gid = cred->fsgid;
+	} else {
+		/*
+		 * Using the euid would make more sense here, but something
+		 * in userland might rely on the old behavior, and this
+		 * shouldn't be a security problem since
+		 * PTRACE_MODE_REALCREDS implies that the caller explicitly
+		 * used a syscall that requests access to another process
+		 * (and not a filesystem syscall to procfs).
+		 */
+		caller_uid = cred->uid;
+		caller_gid = cred->gid;
+	}
 	tcred = __task_cred(task);
-	if (uid_eq(cred->uid, tcred->euid) &&
-	    uid_eq(cred->uid, tcred->suid) &&
-	    uid_eq(cred->uid, tcred->uid)  &&
-	    gid_eq(cred->gid, tcred->egid) &&
-	    gid_eq(cred->gid, tcred->sgid) &&
-	    gid_eq(cred->gid, tcred->gid))
+	if (uid_eq(caller_uid, tcred->euid) &&
+	    uid_eq(caller_uid, tcred->suid) &&
+	    uid_eq(caller_uid, tcred->uid)  &&
+	    gid_eq(caller_gid, tcred->egid) &&
+	    gid_eq(caller_gid, tcred->sgid) &&
+	    gid_eq(caller_gid, tcred->gid))
 		goto ok;
 	if (ptrace_has_cap(tcred->user_ns, mode))
 		goto ok;
@@ -306,7 +329,7 @@ static int ptrace_attach(struct task_struct *task, long request,
 		goto out;
 
 	task_lock(task);
-	retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH);
+	retval = __ptrace_may_access(task, PTRACE_MODE_ATTACH_REALCREDS);
 	task_unlock(task);
 	if (retval)
 		goto unlock_creds;
@@ -364,8 +387,14 @@ unlock_creds:
 	mutex_unlock(&task->signal->cred_guard_mutex);
 out:
 	if (!retval) {
-		wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT,
-			    TASK_UNINTERRUPTIBLE);
+		/*
+		 * We do not bother to change retval or clear JOBCTL_TRAPPING
+		 * if wait_on_bit() was interrupted by SIGKILL. The tracer will
+		 * not return to user-mode, it will exit and clear this bit in
+		 * __ptrace_unlink() if it wasn't already cleared by the tracee;
+		 * and until then nobody can ptrace this task.
+		 */
+		wait_on_bit(&task->jobctl, JOBCTL_TRAPPING_BIT, TASK_KILLABLE);
 		proc_ptrace_connector(task, PTRACE_ATTACH);
 	}