[PATCH 6.0 0846/1073] bpf: prevent leak of lsm program after failed attach

Greg Kroah-Hartman
2022-12-28T16:38:07Z

From: Milan Landaverde <milan@mdaverde.com>

[ Upstream commit e89f3edffb860a0f54a9ed16deadb7a4a1fa3862 ]

In [0], we added the ability to bpf_prog_attach LSM programs to cgroups,
but in our validation to make sure the prog is meant to be attached to
BPF_LSM_CGROUP, we return too early if the check fails. This results in
lack of decrementing prog's refcnt (through bpf_prog_put)
leaving the LSM program alive past the point of the expected lifecycle.
This fix allows for the decrement to take place.

[0] https://lore.kernel.org/all/20220628174314.1216643-4-sdf@google.com/

Fixes: 69fd337a975c ("bpf: per-cgroup lsm flavor")
Signed-off-by: Milan Landaverde <milan@mdaverde.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/r/20221213175714.31963-1-milan@mdaverde.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/bpf/syscall.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0e758911d963..6b6fb7237ebe 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3505,9 +3505,9 @@ static int bpf_prog_attach(const union bpf_attr *attr)
case BPF_PROG_TYPE_LSM:
if (ptype == BPF_PROG_TYPE_LSM &&
prog->expected_attach_type != BPF_LSM_CGROUP)
- return -EINVAL;
-
- ret = cgroup_bpf_prog_attach(attr, ptype, prog);
+ ret = -EINVAL;
+ else
+ ret = cgroup_bpf_prog_attach(attr, ptype, prog);
break;
default:
ret = -EINVAL;
--
2.35.1