Fix compiler warnings about breaking strict-aliasing rules

* system.c (sys_capget, sys_capset): Use proxy unions to cast long*
pointers to cap_user_header_t and cap_user_data_t pointers without
breaking strict-aliasing rules.

Reported-by: Mike Frysinger <vapier@gentoo.org>

diff --git a/system.c b/system.c
index 549844947176e3d065befa5895e53d8eb80e80c5..c44a0168350b908f77d63dd59543ac191313d1a3 100644 (file)
--- a/system.c
+++ b/system.c
@@ -501,37 +501,37 @@ sys_capget(struct tcb *tcp)
        /* cap_user_ types are _pointers_ to (small) structs. */
        /* Structs themselves have no names defined. */
        /* Have to use ugly hack to place them on stack. */
-       cap_user_header_t arg0;
-       cap_user_data_t   arg1;
-       long a0[sizeof(*arg0) / sizeof(long) + 1];
-       long a1[sizeof(*arg1) / sizeof(long) + 1];
-       arg0 = (cap_user_header_t) a0;
-       arg1 = (cap_user_data_t  ) a1;
+       union { cap_user_header_t p; long *a; char *c; } arg0;
+       union { cap_user_data_t p; long *a; char *c; } arg1;
+       long a0[sizeof(*arg0.p) / sizeof(long) + 1];
+       long a1[sizeof(*arg1.p) / sizeof(long) + 1];
+       arg0.a = a0;
+       arg1.a = a1;
 
        if (!entering(tcp)) {
                if (!tcp->u_arg[0])
                        tprints("NULL");
                else if (!verbose(tcp))
                        tprintf("%#lx", tcp->u_arg[0]);
-               else if (umoven(tcp, tcp->u_arg[0], sizeof(*arg0), (char *) arg0) < 0)
+               else if (umoven(tcp, tcp->u_arg[0], sizeof(*arg0.p), arg0.c) < 0)
                        tprints("???");
                else {
-                       tprintf("%#x, %d", arg0->version, arg0->pid);
+                       tprintf("%#x, %d", arg0.p->version, arg0.p->pid);
                }
                tprints(", ");
                if (!tcp->u_arg[1])
                        tprints("NULL");
                else if (!verbose(tcp))
                        tprintf("%#lx", tcp->u_arg[1]);
-               else if (umoven(tcp, tcp->u_arg[1], sizeof(*arg1), (char *) arg1) < 0)
+               else if (umoven(tcp, tcp->u_arg[1], sizeof(*arg1.p), arg1.c) < 0)
                        tprints("???");
                else {
                        tprints("{");
-                       printflags(capabilities, arg1->effective, "CAP_???");
+                       printflags(capabilities, arg1.p->effective, "CAP_???");
                        tprints(", ");
-                       printflags(capabilities, arg1->permitted, "CAP_???");
+                       printflags(capabilities, arg1.p->permitted, "CAP_???");
                        tprints(", ");
-                       printflags(capabilities, arg1->inheritable, "CAP_???");
+                       printflags(capabilities, arg1.p->inheritable, "CAP_???");
                        tprints("}");
                }
        }
@@ -541,37 +541,37 @@ sys_capget(struct tcb *tcp)
 int
 sys_capset(struct tcb *tcp)
 {
-       cap_user_header_t arg0;
-       cap_user_data_t   arg1;
-       long a0[sizeof(*arg0) / sizeof(long) + 1];
-       long a1[sizeof(*arg1) / sizeof(long) + 1];
-       arg0 = (cap_user_header_t) a0;
-       arg1 = (cap_user_data_t  ) a1;
+       union { cap_user_header_t p; long *a; char *c; } arg0;
+       union { cap_user_data_t p; long *a; char *c; } arg1;
+       long a0[sizeof(*arg0.p) / sizeof(long) + 1];
+       long a1[sizeof(*arg1.p) / sizeof(long) + 1];
+       arg0.a = a0;
+       arg1.a = a1;
 
        if (entering(tcp)) {
                if (!tcp->u_arg[0])
                        tprints("NULL");
                else if (!verbose(tcp))
                        tprintf("%#lx", tcp->u_arg[0]);
-               else if (umoven(tcp, tcp->u_arg[0], sizeof(*arg0), (char *) arg0) < 0)
+               else if (umoven(tcp, tcp->u_arg[0], sizeof(*arg0.p), arg0.c) < 0)
                        tprints("???");
                else {
-                       tprintf("%#x, %d", arg0->version, arg0->pid);
+                       tprintf("%#x, %d", arg0.p->version, arg0.p->pid);
                }
                tprints(", ");
                if (!tcp->u_arg[1])
                        tprints("NULL");
                else if (!verbose(tcp))
                        tprintf("%#lx", tcp->u_arg[1]);
-               else if (umoven(tcp, tcp->u_arg[1], sizeof(*arg1), (char *) arg1) < 0)
+               else if (umoven(tcp, tcp->u_arg[1], sizeof(*arg1.p), arg1.c) < 0)
                        tprints("???");
                else {
                        tprints("{");
-                       printflags(capabilities, arg1->effective, "CAP_???");
+                       printflags(capabilities, arg1.p->effective, "CAP_???");
                        tprints(", ");
-                       printflags(capabilities, arg1->permitted, "CAP_???");
+                       printflags(capabilities, arg1.p->permitted, "CAP_???");
                        tprints(", ");
-                       printflags(capabilities, arg1->inheritable, "CAP_???");
+                       printflags(capabilities, arg1.p->inheritable, "CAP_???");
                        tprints("}");
                }
        }