[PATCH] scsi: fix shift out-of-bounds in sg_build_indirect The num variable is set to 0. The variable num gets its value from scatter_elem_sz. However the minimum value of scatter_elem_sz is PAGE_SHIFT. So setting num to PAGE_SIZE when num < PAGE_SIZE.

[Kshitij Paranjape]

Cc: <stable@xxxxxxxxxxxxxxx>
Reported-by: syzbot+270f1c719ee7baab9941@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=270f1c719ee7baab9941
Signed-off-by: Kshitij Paranjape <kshitijvparanjape@xxxxxxxxx>
---
 drivers/scsi/sg.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index effb7e768165..9ae41bb256d7 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1888,6 +1888,7 @@ sg_build_indirect(Sg_scatter_hold * schp, Sg_fd * sfp, int buff_size)
 		if (num < PAGE_SIZE) {
 			scatter_elem_sz = PAGE_SIZE;
 			scatter_elem_sz_prev = PAGE_SIZE;
+			num = scatter_elem_sz;
 		} else
 			scatter_elem_sz_prev = num;
 	}
-- 
2.43.0