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    Subject[PATCH 4.14 100/101] bpf: skip unnecessary capability check
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Chenbo Feng <fengc@google.com>

    commit 0fa4fe85f4724fff89b09741c437cbee9cf8b008 upstream.

    The current check statement in BPF syscall will do a capability check
    for CAP_SYS_ADMIN before checking sysctl_unprivileged_bpf_disabled. This
    code path will trigger unnecessary security hooks on capability checking
    and cause false alarms on unprivileged process trying to get CAP_SYS_ADMIN
    access. This can be resolved by simply switch the order of the statement
    and CAP_SYS_ADMIN is not required anyway if unprivileged bpf syscall is
    allowed.

    Signed-off-by: Chenbo Feng <fengc@google.com>
    Acked-by: Lorenzo Colitti <lorenzo@google.com>
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/bpf/syscall.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/kernel/bpf/syscall.c
    +++ b/kernel/bpf/syscall.c
    @@ -1455,7 +1455,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf
    union bpf_attr attr = {};
    int err;

    - if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled)
    + if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN))
    return -EPERM;

    err = check_uarg_tail_zero(uattr, sizeof(attr), size);

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