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bpf: Handle return value of BPF_PROG_TYPE_STRUCT_OPS prog

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[ Upstream commit 356ed64991c6847a0c4f2e8fa3b1133f7a14f1fc ]

Currently if a function ptr in struct_ops has a return value, its
caller will get a random return value from it, because the return
value of related BPF_PROG_TYPE_STRUCT_OPS prog is just dropped.

So adding a new flag BPF_TRAMP_F_RET_FENTRY_RET to tell bpf trampoline
to save and return the return value of struct_ops prog if ret_size of
the function ptr is greater than 0. Also restricting the flag to be
used alone.

Fixes: 85d33df357 ("bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210914023351.3664499-1-houtao1@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Hou Tao
2021-09-14 10:33:51 +08:00
committed by Greg Kroah-Hartman
parent 12cbdaeeb5
commit d93f65586c
3 changed files with 47 additions and 15 deletions
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7
kernel/bpf/bpf_struct_ops.c
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@@ -367,6 +367,7 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
const struct btf_type *mtype, *ptype;
struct bpf_prog *prog;
u32 moff;
u32 flags;
moff = btf_member_bit_offset(t, member) / 8;
ptype = btf_type_resolve_ptr(btf_vmlinux, member->type, NULL);
@@ -430,10 +431,12 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
tprogs[BPF_TRAMP_FENTRY].progs[0] = prog;
tprogs[BPF_TRAMP_FENTRY].nr_progs = 1;
flags = st_ops->func_models[i].ret_size > 0 ?
BPF_TRAMP_F_RET_FENTRY_RET : 0;
err = arch_prepare_bpf_trampoline(NULL, image,
st_map->image + PAGE_SIZE,
&st_ops->func_models[i], 0,
tprogs, NULL);
&st_ops->func_models[i],
flags, tprogs, NULL);
if (err < 0)
goto reset_unlock;