From: Christian Barcenas <christian@cbarcenas.com>
To: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
netdev@vger.kernel.org
Cc: Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
Christian Barcenas <christian@cbarcenas.com>,
bpf@vger.kernel.org
Subject: [PATCH bpf] bpf: respect CAP_IPC_LOCK in RLIMIT_MEMLOCK check
Date: Wed, 11 Sep 2019 11:18:16 -0700 [thread overview]
Message-ID: <20190911181816.89874-1-christian@cbarcenas.com> (raw)
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@cbarcenas.com>
---
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
next reply other threads:[~2019-09-11 18:18 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 18:18 Christian Barcenas [this message]
2019-09-13 18:48 ` [PATCH bpf] bpf: respect CAP_IPC_LOCK in RLIMIT_MEMLOCK check Yonghong Song
2019-09-16 9:26 ` Daniel Borkmann
2019-09-16 14:09 ` Christian Barcenas
2019-09-16 22:19 ` Alexei Starovoitov
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