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[bpf-next,v2,2/2] bpf: Expose bpf_d_path helper to sleepable LSM hooks

Message ID 20201112200346.404864-3-kpsingh@chromium.org (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series Sleepable LSM Hooks | expand

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netdev/tree_selection success Clearly marked for bpf-next
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netdev/source_inline success Was 0 now: 0
netdev/verify_signedoff success Link
netdev/module_param success Was 0 now: 0
netdev/build_32bit fail Errors and warnings before: 37 this patch: 37
netdev/kdoc success Errors and warnings before: 0 this patch: 0
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netdev/build_allmodconfig_warn success Errors and warnings before: 33 this patch: 33
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netdev/stable success Stable not CCed

Commit Message

KP Singh Nov. 12, 2020, 8:03 p.m. UTC 
From: KP Singh <kpsingh@google.com>

Sleepable hooks are never called from an NMI/interrupt context, so it is
safe to use the bpf_d_path helper in LSM programs attaching to these
hooks.

The helper is not restricted to sleepable programs and merely uses the
list of sleeable hooks as the initial subset of LSM hooks where it can
be used.

Signed-off-by: KP Singh <kpsingh@google.com>
---
 kernel/trace/bpf_trace.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
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Patch

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index e4515b0f62a8..eab1af02c90d 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -16,6 +16,7 @@ 
 #include <linux/syscalls.h>
 #include <linux/error-injection.h>
 #include <linux/btf_ids.h>
+#include <linux/bpf_lsm.h>
 
 #include <uapi/linux/bpf.h>
 #include <uapi/linux/btf.h>
@@ -1178,7 +1179,11 @@  BTF_SET_END(btf_allowlist_d_path)
 
 static bool bpf_d_path_allowed(const struct bpf_prog *prog)
 {
-	return btf_id_set_contains(&btf_allowlist_d_path, prog->aux->attach_btf_id);
+	if (prog->type == BPF_PROG_TYPE_LSM)
+		return bpf_lsm_is_sleepable_hook(prog->aux->attach_btf_id);
+
+	return btf_id_set_contains(&btf_allowlist_d_path,
+				   prog->aux->attach_btf_id);
 }
 
 BTF_ID_LIST_SINGLE(bpf_d_path_btf_ids, struct, path)