tools/bpf/bpftool: fix buffer handling in get_fd_type()

The current check "if (n == sizeof(buf))" is incorrect for detecting
buffer overflow from readlink(). When readlink() fills the entire
buffer, it returns sizeof(buf) but does not null-terminate the string,
leading to potential buffer overrun in subsequent string operations.

Fix by changing the condition to "n >= sizeof(buf)" to properly detect
when the buffer is completely filled, ensuring space is reserved for
null termination.

Signed-off-by: Kaushlendra Kumar <[email protected]>

Author: kaushlen

tools/bpf/bpftool/common.c

@@ -464,7 +464,7 @@ int get_fd_type(int fd)
 		p_err("can't read link type: %s", strerror(errno));
 		return -1;
 	}
-	if (n == sizeof(buf)) {
+	if (n >= sizeof(buf)) {
 		p_err("can't read link type: path too long!");
 		return -1;
 	}