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bpf: prevent leak of lsm program after failed attach

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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: 69fd337a97 ("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
This commit is contained in:
Milan Landaverde 2022-12-13 12:57:14 -05:00 • committed by Daniel Borkmann
parent a8dfde09c9
commit e89f3edffb
1 changed files with 3 additions and 3 deletions
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6
kernel/bpf/syscall.c
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@ -3518,9 +3518,9 @@ 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;