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authorKees Cook <keescook@chromium.org>2019-01-16 10:31:09 -0800
committerJames Morris <james.morris@microsoft.com>2019-01-16 12:00:56 -0800
commit9474f4e7cd71a633fa1ef93b7daefd44bbdfd482 (patch)
tree3484380352e826bd5415a27323d4752d7b1c053a
parenta811dc61559e0c8003f1086c2a4dc8e4d5ae4cb8 (diff)
Yama: Check for pid death before checking ancestry
It's possible that a pid has died before we take the rcu lock, in which case we can't walk the ancestry list as it may be detached. Instead, check for death first before doing the walk. Reported-by: syzbot+a9ac39bf55329e206219@syzkaller.appspotmail.com Fixes: 2d514487faf1 ("security: Yama LSM") Cc: stable@vger.kernel.org Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: James Morris <james.morris@microsoft.com>
-rw-r--r--security/yama/yama_lsm.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c
index ffda91a4a1aa..02514fe558b4 100644
--- a/security/yama/yama_lsm.c
+++ b/security/yama/yama_lsm.c
@@ -368,7 +368,9 @@ static int yama_ptrace_access_check(struct task_struct *child,
break;
case YAMA_SCOPE_RELATIONAL:
rcu_read_lock();
- if (!task_is_descendant(current, child) &&
+ if (!pid_alive(child))
+ rc = -EPERM;
+ if (!rc && !task_is_descendant(current, child) &&
!ptracer_exception_found(current, child) &&
!ns_capable(__task_cred(child)->user_ns, CAP_SYS_PTRACE))
rc = -EPERM;