Fix: sessiond: fix possible buffer overflow warning

When compiling with clang-14 on Ubuntu 20.04, I get:

      CC       lttng-syscall.lo
    /home/smarchi/src/lttng-tools/src/bin/lttng-sessiond/lttng-syscall.c:70:13: error: 'fscanf' may overflow; destination buffer in argument 4 has size 255, but the corresponding specifier may require size 256 [-Werror,-Wfortify-source]
                                    &index, name, &bitness) == 3) {
                                            ^

I think the compiler is right, we read a string when length up to 255 in
a buffer of size 255.  We need one more byte for the NULL terminator,
fix that.

Change-Id: I6b2eec401af3ef6230dd4b6c8559032de9b54584
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng-sessiond/lttng-syscall.c b/src/bin/lttng-sessiond/lttng-syscall.c
index 16eead6260783fd0d6ce1742004489623133e129..b6a9a53acd757dc1888231674103ea74583da97b 100644 (file)
--- a/src/bin/lttng-sessiond/lttng-syscall.c
+++ b/src/bin/lttng-sessiond/lttng-syscall.c
@@ -39,6 +39,10 @@ int syscall_init_table(int tracer_fd)
        uint32_t bitness;
        char name[SYSCALL_NAME_LEN];
 
+#if (SYSCALL_NAME_LEN == 255)
+#define SYSCALL_NAME_LEN_SCANF_IS_A_BROKEN_API "254"
+#endif
+
        DBG3("Syscall init system call table");
 
        fd = kernctl_syscall_list(tracer_fd);
@@ -65,7 +69,7 @@ int syscall_init_table(int tracer_fd)
 
        while (fscanf(fp,
                                "syscall { index = %zu; \
-                               name = %" XSTR(SYSCALL_NAME_LEN) "[^;]; \
+                               name = %" SYSCALL_NAME_LEN_SCANF_IS_A_BROKEN_API "[^;]; \
                                bitness = %u; };\n",
                                &index, name, &bitness) == 3) {
                at_least_one_syscall = true;