[PATCH] fs: Avoid signed overflow UBSAN warning

[Hongbo Yao]

I ran into this:
        UBSAN: Undefined behaviour in fs/read_write.c:251:11
        signed integer overflow:
        9223372036854775805 + 9223372036854775805 cannot be represented in
        type 'long long int'

Use unsigned types to do math, it doesn't throw a UBSAN warning
when it does overflow.This patch doesn't change generated code.

Signed-off-by: Hongbo Yao <yaohon...@huawei.com>
---
 fs/read_write.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 8f08d4a2aa9a..0509e81afc8e 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -248,7 +248,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int 
whence)
                                retval = file->f_pos;
                                goto out;
                        }
-                       offset += file->f_pos;
+                       offset = (u64)file->f_pos + (u64)offset;
                        break;
                case SEEK_DATA:
                        /*
-- 
2.20.1