[PATCH v2] x86/bpf: do not audit capability check in do_jit()

[PATCH v2] x86/bpf: do not audit capability check in do_jit()

[Ondrej Mosnacek]

The failure of this check only results in a security mitigation being
applied, slightly affecting performance of the compiled BPF program. It
doesn't result in a failed syscall, an thus auditing a failed LSM
permission check for it is unwanted. For example with SELinux, it causes
a denial to be reported for confined processes running as root, which
tends to be flagged as a problem to be fixed in the policy. Yet
dontauditing or allowing CAP_SYS_ADMIN to the domain may not be
desirable, as it would allow/silence also other checks - either going
against the principle of least privilege or making debugging potentially
harder.

Fix it by changing it from capable() to ns_capable_noaudit(), which
instructs the LSMs to not audit the resulting denials.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=2369326
Fixes: d4e89d212d40 ("x86/bpf: Call branch history clearing sequence on exit")
Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
---

v1: https://lore.kernel.org/selinux/20250806143105.915748-1-omosnace@redhat.com/
Changes in v2:
 - just silence the audit records instead of switching to bpf_capable()

 arch/x86/net/bpf_jit_comp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index d4c93d9e73e40..de5083cb1d374 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -2701,7 +2701,7 @@ emit_jmp:
 			/* Update cleanup_addr */
 			ctx->cleanup_addr = proglen;
 			if (bpf_prog_was_classic(bpf_prog) &&
-			    !capable(CAP_SYS_ADMIN)) {
+			    !ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN)) {
 				u8 *ip = image + addrs[i - 1];
 
 				if (emit_spectre_bhb_barrier(&prog, ip, bpf_prog))
-- 
2.51.0

Re: [PATCH v2] x86/bpf: do not audit capability check in do_jit()

[Paul Moore]

On Tue, Oct 21, 2025 at 8:28 AM Ondrej Mosnacek <omosnace@redhat.com> wrote:
>
> The failure of this check only results in a security mitigation being
> applied, slightly affecting performance of the compiled BPF program. It
> doesn't result in a failed syscall, an thus auditing a failed LSM
> permission check for it is unwanted. For example with SELinux, it causes
> a denial to be reported for confined processes running as root, which
> tends to be flagged as a problem to be fixed in the policy. Yet
> dontauditing or allowing CAP_SYS_ADMIN to the domain may not be
> desirable, as it would allow/silence also other checks - either going
> against the principle of least privilege or making debugging potentially
> harder.
>
> Fix it by changing it from capable() to ns_capable_noaudit(), which
> instructs the LSMs to not audit the resulting denials.
>
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=2369326
> Fixes: d4e89d212d40 ("x86/bpf: Call branch history clearing sequence on exit")
> Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
> ---
>
> v1: https://lore.kernel.org/selinux/20250806143105.915748-1-omosnace@redhat.com/
> Changes in v2:
>  - just silence the audit records instead of switching to bpf_capable()
>
>  arch/x86/net/bpf_jit_comp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Paul Moore <paul@paul-moore.com>

-- 
paul-moore.com

Re: [PATCH v2] x86/bpf: do not audit capability check in do_jit()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Tue, 21 Oct 2025 14:27:58 +0200 you wrote:
> The failure of this check only results in a security mitigation being
> applied, slightly affecting performance of the compiled BPF program. It
> doesn't result in a failed syscall, an thus auditing a failed LSM
> permission check for it is unwanted. For example with SELinux, it causes
> a denial to be reported for confined processes running as root, which
> tends to be flagged as a problem to be fixed in the policy. Yet
> dontauditing or allowing CAP_SYS_ADMIN to the domain may not be
> desirable, as it would allow/silence also other checks - either going
> against the principle of least privilege or making debugging potentially
> harder.
> 
> [...]

Here is the summary with links:
  - [v2] x86/bpf: do not audit capability check in do_jit()
    https://git.kernel.org/bpf/bpf/c/881a9c9cb785

You are awesome, thank you!
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