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Diffstat (limited to 'kernel/ptrace.c')
-rw-r--r--kernel/ptrace.c49
1 files changed, 39 insertions, 10 deletions
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);
}