From f075dce66c6039bb97b762b592a6db6d79e4350a Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 10 Jul 2018 17:02:17 -0700 Subject: [PATCH] scsi sg: remove incorrect scsi command checking logic The SCSI_IOCTL_SEND_COMMAND ioctl has interesting scsi command "security" checking. If the file was opened read-only (but only in that case), it will fetch the first byte of the command from user space, and do "sg_allow_access()" on it. That, in turn, will check that "blk_verify_command()" is ok with that command byte. If that passes, it will then do call "sg_scsi_ioctl()" to execute the command. This is entirely nonsensical for several reasons. It's nonsensical simply because it's racy: after it copies the command byte from user mode to check it, user mode could just change the byte before it is actually submitted later by "sg_scsi_ioctl()". But it is nonsensical also because "sg_scsi_ioctl()" itself already does blk_verify_command() on the command properly after it has been copied from user space. So it is an incorrect implementation of a pointless check. Remove it. Signed-off-by: Linus Torvalds --- drivers/scsi/sg.c | 9 --------- 1 file changed, 9 deletions(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index cd2fdac000c9..4f3450793273 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -1103,15 +1103,6 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg) case SCSI_IOCTL_SEND_COMMAND: if (atomic_read(&sdp->detaching)) return -ENODEV; - if (read_only) { - unsigned char opcode = WRITE_6; - Scsi_Ioctl_Command __user *siocp = p; - - if (copy_from_user(&opcode, siocp->data, 1)) - return -EFAULT; - if (sg_allow_access(filp, &opcode)) - return -EPERM; - } return sg_scsi_ioctl(sdp->device->request_queue, NULL, filp->f_mode, p); case SG_SET_DEBUG: result = get_user(val, ip);