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    Subject[PATCH 5.4 152/158] ptrace: Set PF_SUPERPRIV when checking capability
    Date
    From: Mickaël Salaün <mic@linux.microsoft.com>

    commit cf23705244c947151179f929774fabf71e239eee upstream.

    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
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/ptrace.c | 16 +++++-----------
    1 file changed, 5 insertions(+), 11 deletions(-)

    --- a/kernel/ptrace.c
    +++ b/kernel/ptrace.c
    @@ -264,17 +264,11 @@ static int ptrace_check_attach(struct ta
    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 ta
    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 @@ ok:
    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);

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