[PATCH 1/7] xyz-modem: Fix crash after cancelling transfer

[Pali Rohár]

Variable xyz.len is set to -1 on error. At the end xyzModem_stream_read()
function calls memcpy() with length from variable xyz.len. If this variable
is set to -1 then value passed to memcpy is casted to unsigned value, which
means to copy whole address space. Which then cause U-Boot crash. E.g. on
arm64 it cause CPU crash: "Synchronous Abort" handler, esr 0x96000006

Fix this issue by checking that value stored in xyz.len is valid prior
trying to use it.

Signed-off-by: Pali Rohár <pali at kernel.org>
---
 common/xyzModem.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/common/xyzModem.c b/common/xyzModem.c
index fc3459ebbafe..b1b72aae0baf 100644
--- a/common/xyzModem.c
+++ b/common/xyzModem.c
@@ -494,7 +494,7 @@ xyzModem_stream_read (char *buf, int size, int *err)
   total = 0;
   stat = xyzModem_cancel;
   /* Try and get 'size' bytes into the buffer */
-  while (!xyz.at_eof && (size > 0))
+  while (!xyz.at_eof && xyz.len >= 0 && (size > 0))
     {
       if (xyz.len == 0)
 	{
@@ -587,7 +587,7 @@ xyzModem_stream_read (char *buf, int size, int *err)
 	    }
 	}
       /* Don't "read" data from the EOF protocol package */
-      if (!xyz.at_eof)
+      if (!xyz.at_eof && xyz.len > 0)
 	{
 	  len = xyz.len;
 	  if (size < len)
-- 
2.20.1