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[bpf-next,2/7] libbpf: handle yet another corner case of nulling out struct_ops program

Message ID 20240507001335.1445325-3-andrii@kernel.org (mailing list archive)
State Accepted
Commit e18e2e70dbd1ee3099049557060067b6ec703efa
Delegated to: BPF
Headers show
Series libbpf: further struct_ops fixes and improvements | expand

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Commit Message

Andrii Nakryiko May 7, 2024, 12:13 a.m. UTC 
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: 0737df6de946 ("libbpf: better fix for handling nulled-out struct_ops program")
Fixes: f973fccd43d3 ("libbpf: handle nulled-out program in struct_ops correctly")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
 tools/lib/bpf/libbpf.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 7d77a1b158ce..04de4fb81785 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -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);