s390/disassembler: prevent endless loop in print_fn_code()

If the size of the opcode to be printed is larger than "len" we'll
see an overflow of an unsigned long value, which means that the
while loop within print_fn_code() will loop quite a long time until
there is the next chance for an exit.
So add an early exit check.

Reported-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/s390/kernel/dis.c b/arch/s390/kernel/dis.c
index 7f4a4a8c847c..be87d3e05a5b 100644
--- a/arch/s390/kernel/dis.c
+++ b/arch/s390/kernel/dis.c
@@ -1862,6 +1862,8 @@ void print_fn_code(unsigned char *code, unsigned long len)
         while (len) {
                 ptr = buffer;
                 opsize = insn_length(*code);
+                if (opsize > len)
+                        break;
                 ptr += sprintf(ptr, "%p: ", code);
                 for (i = 0; i < opsize; i++)
                         ptr += sprintf(ptr, "%02x", code[i]);