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[bpf-next] libbpf: skip modules BTF loading when CAP_SYS_ADMIN is missing

Message ID 20230626093614.21270-1-andreaterzolo3@gmail.com (mailing list archive)
State Accepted
Commit 2d2c95162de8fc6875c9c3d39f83527ae28e2e8a
Delegated to: BPF
Headers show
Series [bpf-next] libbpf: skip modules BTF loading when CAP_SYS_ADMIN is missing | expand

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netdev/fixes_present success Fixes tag not required for -next series
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Commit Message

Andrea Terzolo June 26, 2023, 9:36 a.m. UTC 
If during CO-RE relocations libbpf is not able to find the target type
in the running kernel BTF, it searches for it in modules' BTF.
The downside of this approach is that loading modules' BTF requires
CAP_SYS_ADMIN and this prevents BPF applications from running with more
granular capabilities (e.g. CAP_BPF) when they don't need to search
types into modules' BTF.

This patch skips by default modules' BTF loading phase when
CAP_SYS_ADMIN is missing.

Link: https://lore.kernel.org/CAGQdkDvYU_e=_NX+6DRkL_-TeH3p+QtsdZwHkmH0w3Fuzw0C4w@mail.gmail.com
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Co-developed-by: Federico Di Pierro <nierro92@gmail.com>
Signed-off-by: Federico Di Pierro <nierro92@gmail.com>
Signed-off-by: Andrea Terzolo <andreaterzolo3@gmail.com>
---
 tools/lib/bpf/libbpf.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

patchwork-bot+netdevbpf@kernel.org June 30, 2023, 7:40 p.m. UTC | #1 
Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Mon, 26 Jun 2023 11:36:14 +0200 you wrote:
> If during CO-RE relocations libbpf is not able to find the target type
> in the running kernel BTF, it searches for it in modules' BTF.
> The downside of this approach is that loading modules' BTF requires
> CAP_SYS_ADMIN and this prevents BPF applications from running with more
> granular capabilities (e.g. CAP_BPF) when they don't need to search
> types into modules' BTF.
> 
> [...]

Here is the summary with links:
  - [bpf-next] libbpf: skip modules BTF loading when CAP_SYS_ADMIN is missing
    https://git.kernel.org/bpf/bpf-next/c/2d2c95162de8

You are awesome, thank you!
diff mbox series

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 214f828ece6b..d793a1bfb70c 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -5471,6 +5471,10 @@  static int load_module_btfs(struct bpf_object *obj)
 		err = bpf_btf_get_next_id(id, &id);
 		if (err && errno == ENOENT)
 			return 0;
+		if (err && errno == EPERM) {
+			pr_debug("skipping module BTFs loading, missing privileges\n");
+			return 0;
+		}
 		if (err) {
 			err = -errno;
 			pr_warn("failed to iterate BTF objects: %d\n", err);