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>
---
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;
}
--
2.23.0
