[PATCH RESEND] scsi: megaraid_sas: fix panic on loading firmware crashdump

[Junxiao Bi]

While loading fw crashdump in function fw_crash_buffer_show(),
left bytes in one dma chunk was not checked, if copying size
over it, overflow access will cause kernel panic.

Signed-off-by: Junxiao Bi <junxiao...@oracle.com>
---
 drivers/scsi/megaraid/megaraid_sas_base.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/scsi/megaraid/megaraid_sas_base.c 
b/drivers/scsi/megaraid/megaraid_sas_base.c
index 80ab9700f1de..3eef0858fa8e 100644
--- a/drivers/scsi/megaraid/megaraid_sas_base.c
+++ b/drivers/scsi/megaraid/megaraid_sas_base.c
@@ -3153,6 +3153,7 @@ fw_crash_buffer_show(struct device *cdev,
                (struct megasas_instance *) shost->hostdata;
        u32 size;
        unsigned long dmachunk = CRASH_DMA_BUF_SIZE;
+       unsigned long chunk_left_bytes;
        unsigned long src_addr;
        unsigned long flags;
        u32 buff_offset;
@@ -3176,6 +3177,8 @@ fw_crash_buffer_show(struct device *cdev,
        }
 
        size = (instance->fw_crash_buffer_size * dmachunk) - buff_offset;
+       chunk_left_bytes = dmachunk - (buff_offset % dmachunk);
+       size = (size > chunk_left_bytes) ? chunk_left_bytes : size;
        size = (size >= PAGE_SIZE) ? (PAGE_SIZE - 1) : size;
 
        src_addr = (unsigned long)instance->crash_buf[buff_offset / dmachunk] +
-- 
2.17.1