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libbpf: handle yet another corner case of nulling out struct_ops program

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There is yet another corner case where user can set STRUCT_OPS program
reference in STRUCT_OPS map to NULL, but libbpf will fail to disable
autoload for such BPF program. This time it's the case of "new" kernel
which has type information about callback field, but user explicitly
nulled-out program reference from user-space after opening BPF object.

Fix, hopefully, the last remaining unhandled case.

Fixes: 0737df6de9 ("libbpf: better fix for handling nulled-out struct_ops program")
Fixes: f973fccd43 ("libbpf: handle nulled-out program in struct_ops correctly")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240507001335.1445325-3-andrii@kernel.org
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Andrii Nakryiko 2024-05-06 17:13:30 -07:00 committed by Martin KaFai Lau
parent 8374b56b1d
commit e18e2e70db
1 changed files with 9 additions and 1 deletions
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10
tools/lib/bpf/libbpf.c
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@ -1193,11 +1193,19 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map)
}
if (btf_is_ptr(mtype)) {
/* Update the value from the shadow type */
prog = *(void **)mdata;
/* just like for !kern_member case above, reset declaratively
* set (at compile time) program's autload to false,
* if user replaced it with another program or NULL
*/
if (st_ops->progs[i] && st_ops->progs[i] != prog)
st_ops->progs[i]->autoload = false;
/* Update the value from the shadow type */
st_ops->progs[i] = prog;
if (!prog)
continue;
if (!is_valid_st_ops_program(obj, prog)) {
pr_warn("struct_ops init_kern %s: member %s is not a struct_ops program\n",
map->name, mname);