Check the `readn()` return value in `read_attr()` if there are remaining
header bytes to read (previously, the return value was being ignored).

Fixes: 69996df486fc3 ("perf tools: Enable reading of perf.data files from different ABI rev")
Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>
---
 tools/perf/util/header.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index e3cdc3b7b4ab..09dfd95e350c 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -4161,6 +4161,11 @@ static int read_attr(int fd, struct perf_header *ph,
 		ptr += PERF_ATTR_SIZE_VER0;
 
 		ret = readn(fd, ptr, left);
+		if (ret <= 0) {
+			pr_debug("cannot read %zu remaining bytes of header attr\n",
+				 left);
+			return -1;
+		}
 	}
 	/* read perf_file_section, ids are read in caller */
 	ret = readn(fd, &f_attr->ids, sizeof(f_attr->ids));
-- 
2.49.0