[PATCH v1 2/2] perf cap: If capability is missing still perform root test

[Ian Rogers <irogers@google.com>]

Refine the capability checking logic in perf_cap__capable() to in the
event the capability is missing do the fallback used_root
test. Previously this was only performed when the capability syscall
failed.

Fixes: e25ebda78e23 ("perf cap: Tidy up and improve capability testing")
Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/cap.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/cap.c b/tools/perf/util/cap.c
index ac6d1d9a523d..a2baecbc3145 100644
--- a/tools/perf/util/cap.c
+++ b/tools/perf/util/cap.c
@@ -20,6 +20,7 @@ bool perf_cap__capable(int cap, bool *used_root)
 	};
 	struct __user_cap_data_struct data[MAX_LINUX_CAPABILITY_U32S] = {};
 	__u32 cap_val;
+	bool has_cap = false;
 
 	*used_root = false;
 	while (syscall(SYS_capget, &header, &data[0]) == -1) {
@@ -37,12 +38,21 @@ bool perf_cap__capable(int cap, bool *used_root)
 	if (cap >= 32) {
 		if (header.version == _LINUX_CAPABILITY_VERSION_3) {
 			cap_val = data[1].effective;
+			has_cap = (cap_val & (1U << (cap & 0x1f))) != 0;
 		} else {
 			/* Capability beyond 32 is requested but only 32 are supported. */
-			return false;
+			has_cap = false;
 		}
 	} else {
 		cap_val = data[0].effective;
+		has_cap = (cap_val & (1U << (cap & 0x1f))) != 0;
 	}
-	return (cap_val & (1 << (cap & 0x1f))) != 0;
+
+	if (has_cap) {
+		*used_root = false;
+		return true;
+	}
+
+	*used_root = true;
+	return geteuid() == 0;
 }
-- 
2.55.0.795.g602f6c329a-goog