On 9/11/19 7:18 PM, Christian Barcenas wrote:
> A process can lock memory addresses into physical RAM explicitly
> (via mlock, mlockall, shmctl, etc.) or implicitly (via VFIO,
> perf ring-buffers, bpf maps, etc.), subject to RLIMIT_MEMLOCK limits.
>
> CAP_IPC_LOCK allows a process to exceed these limits, and throughout
> the kernel this capability is checked before allowing/denying an attempt
> to lock memory regions into RAM.
>
> Because bpf locks its programs and maps into RAM, it should respect
> CAP_IPC_LOCK. Previously, bpf would return EPERM when RLIMIT_MEMLOCK was
> exceeded by a privileged process, which is contrary to documented
> RLIMIT_MEMLOCK+CAP_IPC_LOCK behavior.
>
> Fixes: aaac3ba95e4c ("bpf: charge user for creation of BPF maps and programs")
> Signed-off-by: Christian Barcenas <christian@xxxxxxxxxxxxx>
Acked-by: Yonghong Song <yhs@xxxxxx>
> ---
> kernel/bpf/syscall.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> index 272071e9112f..e551961f364b 100644
> --- a/kernel/bpf/syscall.c
> +++ b/kernel/bpf/syscall.c
> @@ -183,8 +183,9 @@ void bpf_map_init_from_attr(struct bpf_map *map, union bpf_attr *attr)
> static int bpf_charge_memlock(struct user_struct *user, u32 pages)
> {
> unsigned long memlock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> + unsigned long locked = atomic_long_add_return(pages, &user->locked_vm);
>
> - if (atomic_long_add_return(pages, &user->locked_vm) > memlock_limit) {
> + if (locked > memlock_limit && !capable(CAP_IPC_LOCK)) {
> atomic_long_sub(pages, &user->locked_vm);
> return -EPERM;
> }
> @@ -1231,7 +1232,7 @@ int __bpf_prog_charge(struct user_struct *user, u32 pages)
>
> if (user) {
> user_bufs = atomic_long_add_return(pages, &user->locked_vm);
> - if (user_bufs > memlock_limit) {
> + if (user_bufs > memlock_limit && !capable(CAP_IPC_LOCK)) {
> atomic_long_sub(pages, &user->locked_vm);
> return -EPERM;
> }
>
