powerpc/le: Big endian arguments for ppc_rtas()

The ppc_rtas() syscall allows userspace to interact directly with RTAS.
For the moment, it assumes every thing is big endian and returns either
EINVAL or EFAULT when called in a little endian environment.

As suggested by Benjamin, to avoid bugs when userspace wants to pass
a non 32 bit value to RTAS, it is far better to stick with a simple
rationale: ppc_rtas() should be called with a big endian rtas_args
structure.

With this patch, it is now up to userspace to forge big endian arguments,
as expected by RTAS.

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 4cf674d7d5ae184b14c0c4e08985dfe1ad4779a1..f386296ff3785cbf907e9311be50b87a046f45fd 100644 (file)
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -1013,12 +1013,13 @@ struct pseries_errorlog *get_pseries_errorlog(struct rtas_error_log *log,
        return NULL;
 }
 
+/* We assume to be passed big endian arguments */
 asmlinkage int ppc_rtas(struct rtas_args __user *uargs)
 {
        struct rtas_args args;
        unsigned long flags;
        char *buff_copy, *errbuf = NULL;
-       int nargs;
+       int nargs, nret, token;
        int rc;
 
        if (!capable(CAP_SYS_ADMIN))
@@ -1027,10 +1028,13 @@ asmlinkage int ppc_rtas(struct rtas_args __user *uargs)
        if (copy_from_user(&args, uargs, 3 * sizeof(u32)) != 0)
                return -EFAULT;
 
-       nargs = args.nargs;
+       nargs = be32_to_cpu(args.nargs);
+       nret  = be32_to_cpu(args.nret);
+       token = be32_to_cpu(args.token);
+
        if (nargs > ARRAY_SIZE(args.args)
-           || args.nret > ARRAY_SIZE(args.args)
-           || nargs + args.nret > ARRAY_SIZE(args.args))
+           || nret > ARRAY_SIZE(args.args)
+           || nargs + nret > ARRAY_SIZE(args.args))
                return -EINVAL;
 
        /* Copy in args. */
@@ -1038,14 +1042,14 @@ asmlinkage int ppc_rtas(struct rtas_args __user *uargs)
                           nargs * sizeof(rtas_arg_t)) != 0)
                return -EFAULT;
 
-       if (args.token == RTAS_UNKNOWN_SERVICE)
+       if (token == RTAS_UNKNOWN_SERVICE)
                return -EINVAL;
 
        args.rets = &args.args[nargs];
-       memset(args.rets, 0, args.nret * sizeof(rtas_arg_t));
+       memset(args.rets, 0, nret * sizeof(rtas_arg_t));
 
        /* Need to handle ibm,suspend_me call specially */
-       if (args.token == ibm_suspend_me_token) {
+       if (token == ibm_suspend_me_token) {
                rc = rtas_ibm_suspend_me(&args);
                if (rc)
                        return rc;
@@ -1062,7 +1066,7 @@ asmlinkage int ppc_rtas(struct rtas_args __user *uargs)
 
        /* A -1 return code indicates that the last command couldn't
           be completed due to a hardware error. */
-       if (args.rets[0] == -1)
+       if (be32_to_cpu(args.rets[0]) == -1)
                errbuf = __fetch_rtas_last_error(buff_copy);
 
        unlock_rtas(flags);
@@ -1077,7 +1081,7 @@ asmlinkage int ppc_rtas(struct rtas_args __user *uargs)
        /* Copy out args. */
        if (copy_to_user(uargs->args + nargs,
                         args.args + nargs,
-                        args.nret * sizeof(rtas_arg_t)) != 0)
+                        nret * sizeof(rtas_arg_t)) != 0)
                return -EFAULT;
 
        return 0;