The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From cf23705244c947151179f929774fabf71e239eee Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= mic@linux.microsoft.com Date: Fri, 30 Oct 2020 13:38:48 +0100 Subject: [PATCH] ptrace: Set PF_SUPERPRIV when checking capability MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit

Commit 69f594a38967 ("ptrace: do not audit capability check when outputing /proc/pid/stat") replaced the use of ns_capable() with has_ns_capability{,_noaudit}() which doesn't set PF_SUPERPRIV.

Commit 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()") replaced has_ns_capability{,_noaudit}() with security_capable(), which doesn't set PF_SUPERPRIV neither.

Since commit 98f368e9e263 ("kernel: Add noaudit variant of ns_capable()"), a new ns_capable_noaudit() helper is available. Let's use it!

As a result, the signature of ptrace_has_cap() is restored to its original one.

Cc: Christian Brauner christian.brauner@ubuntu.com Cc: Eric Paris eparis@redhat.com Cc: Jann Horn jannh@google.com Cc: Kees Cook keescook@chromium.org Cc: Oleg Nesterov oleg@redhat.com Cc: Serge E. Hallyn serge@hallyn.com Cc: Tyler Hicks tyhicks@linux.microsoft.com Cc: stable@vger.kernel.org Fixes: 6b3ad6649a4c ("ptrace: reintroduce usage of subjective credentials in ptrace_has_cap()") Fixes: 69f594a38967 ("ptrace: do not audit capability check when outputing /proc/pid/stat") Signed-off-by: Mickaël Salaün mic@linux.microsoft.com Reviewed-by: Jann Horn jannh@google.com Signed-off-by: Kees Cook keescook@chromium.org Link: https://lore.kernel.org/r/20201030123849.770769-2-mic@digikod.net

diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 43d6179508d6..79de1294f8eb 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -264,17 +264,11 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) return ret; }

-static bool ptrace_has_cap(const struct cred *cred, struct user_namespace *ns, - unsigned int mode) +static bool ptrace_has_cap(struct user_namespace *ns, unsigned int mode) { - int ret; - if (mode & PTRACE_MODE_NOAUDIT) - ret = security_capable(cred, ns, CAP_SYS_PTRACE, CAP_OPT_NOAUDIT); - else - ret = security_capable(cred, ns, CAP_SYS_PTRACE, CAP_OPT_NONE); - - return ret == 0; + return ns_capable_noaudit(ns, CAP_SYS_PTRACE); + return ns_capable(ns, CAP_SYS_PTRACE); }

/* Returns 0 on success, -errno on denial. */ @@ -326,7 +320,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) gid_eq(caller_gid, tcred->sgid) && gid_eq(caller_gid, tcred->gid)) goto ok; - if (ptrace_has_cap(cred, tcred->user_ns, mode)) + if (ptrace_has_cap(tcred->user_ns, mode)) goto ok; rcu_read_unlock(); return -EPERM; @@ -345,7 +339,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) mm = task->mm; if (mm && ((get_dumpable(mm) != SUID_DUMP_USER) && - !ptrace_has_cap(cred, mm->user_ns, mode))) + !ptrace_has_cap(mm->user_ns, mode))) return -EPERM;

return security_ptrace_access_check(task, mode);