diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/cred.c | 9 | ||||
| -rw-r--r-- | kernel/ptrace.c | 10 |
2 files changed, 19 insertions, 0 deletions
diff --git a/kernel/cred.c b/kernel/cred.c index 5f264fb5737d..7b925925be95 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -447,6 +447,15 @@ int commit_creds(struct cred *new) if (task->mm) set_dumpable(task->mm, suid_dumpable); task->pdeath_signal = 0; + /* + * If a task drops privileges and becomes nondumpable, + * the dumpability change must become visible before + * the credential change; otherwise, a __ptrace_may_access() + * racing with this change may be able to attach to a task it + * shouldn't be able to attach to (as if the task had dropped + * privileges without becoming nondumpable). + * Pairs with a read barrier in __ptrace_may_access(). + */ smp_wmb(); } diff --git a/kernel/ptrace.c b/kernel/ptrace.c index df06d2fcbb92..f447f1e36185 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -322,6 +322,16 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) return -EPERM; ok: rcu_read_unlock(); + /* + * If a task drops privileges and becomes nondumpable (through a syscall + * like setresuid()) while we are trying to access it, we must ensure + * that the dumpability is read after the credentials; otherwise, + * we may be able to attach to a task that we shouldn't be able to + * attach to (as if the task had dropped privileges without becoming + * nondumpable). + * Pairs with a write barrier in commit_creds(). + */ + smp_rmb(); mm = task->mm; if (mm && ((get_dumpable(mm) != SUID_DUMP_USER) && |