powerpc/rtas: Fix array overrun in ppc_rtas() syscall
If ppc_rtas() is called with args.nargs == 16 and args.nret == 0,
args.rets is set to point to &args.args[16], which is beyond the end of
the args.args array. This results in a minor read overrun of the array
when we check the first return code (which, per PAPR, is a required
output of all RTAS calls) to see if there's been a hardware error.
Change the nargs/nret check to ensure nargs is <= 15, allowing room for
the status code. Users shouldn't be calling with nret == 0, but there's
no real harm if they do, so we don't stop them.
Signed-off-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 28736ff..8da209f 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -1070,7 +1070,7 @@
nret = be32_to_cpu(args.nret);
token = be32_to_cpu(args.token);
- if (nargs > ARRAY_SIZE(args.args)
+ if (nargs >= ARRAY_SIZE(args.args)
|| nret > ARRAY_SIZE(args.args)
|| nargs + nret > ARRAY_SIZE(args.args))
return -EINVAL;