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Subject[PATCH] powerpc/le: big endian arguments for ppc_rtas()
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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>
---

Ben,

The chunk with the -1 return code check may look a bit pedantic. Please feel
free to kill it. :)

Cheers.

--
Greg

arch/powerpc/kernel/rtas.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 4cf674d..f386296 100644
--- 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;


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