[PATCH] arch: sparc: kernel: check the memory length before use strcpy().

[Chen Gang <gang.chen@asianux.com>]

For the related next strcpy(), the destination length is less than 512,
but the source maximize length may be 'OPROMMAXPARAM' (4096) which is
more than 512.

One work flow may:
  openprom_sunos_ioctl() ->  if (cmd == OPROMSETOPT)
    getstrings() ->  will alloc buffer with size 'OPROMMAXPARAM'.
    opromsetopt() ->  devide the buffer into 'var' and 'value'
      of_set_property() -> pass
        prom_setprop() -> pass
          ldom_set_var()

And do not mind the additional 4 alignment buffer increasing, since
'sizeof(pkt) - sizeof(pkt.header)' is 4 alignment at least.


Signed-off-by: Chen Gang <gang.chen@asianux.com>
---
 arch/sparc/kernel/ds.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/sparc/kernel/ds.c b/arch/sparc/kernel/ds.c
index 5ef48da..11d460f 100644
--- a/arch/sparc/kernel/ds.c
+++ b/arch/sparc/kernel/ds.c
@@ -783,6 +783,16 @@ void ldom_set_var(const char *var, const char *value)
 		char  *base, *p;
 		int msg_len, loops;
 
+		if (strlen(var) + strlen(value) + 2 >
+		    sizeof(pkt) - sizeof(pkt.header)) {
+			printk(KERN_ERR PFX
+				"contents length: %zu, which more than max: %lu,"
+				"so could not set (%s) variable to (%s).\n",
+				strlen(var) + strlen(value) + 2,
+				sizeof(pkt) - sizeof(pkt.header), var, value);
+			return;
+		}
+
 		memset(&pkt, 0, sizeof(pkt));
 		pkt.header.data.tag.type = DS_DATA;
 		pkt.header.data.handle = cp->handle;
-- 
1.7.11.7