[PATCH] scsi: sg: allocate with __GFP_ZERO in sg_build_indirect()

[Paolo Pisati]

From: Alexander Potapenko <glider at google.com>

CVE-2018-1000204

This shall help avoid copying uninitialized memory to the userspace when
calling ioctl(fd, SG_IO) with an empty command.

Reported-by: syzbot+7d26fc1eea198488deab at syzkaller.appspotmail.com
Cc: stable at vger.kernel.org
Signed-off-by: Alexander Potapenko <glider at google.com>
Acked-by: Douglas Gilbert <dgilbert at interlog.com>
Reviewed-by: Johannes Thumshirn <jthumshirn at suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen at oracle.com>
(cherry picked from commit a45b599ad808c3c982fdcdc12b0b8611c2f92824)
Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
---
 drivers/scsi/sg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 47b8f7b..1ab6147 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -1826,7 +1826,7 @@ retry:
 		num = (rem_sz > scatter_elem_sz_prev) ?
 			scatter_elem_sz_prev : rem_sz;
 
-		schp->pages[k] = alloc_pages(gfp_mask, order);
+		schp->pages[k] = alloc_pages(gfp_mask | __GFP_ZERO, order);
 		if (!schp->pages[k])
 			goto out;
 
-- 
2.7.4