Commit d9fc5617 authored Oct 17, 2019 by Al Viro Committed by Martin K. Petersen Nov 06, 2019

scsi: sg: sg_new_write(): don't bother with access_ok

... just use copy_from_user().  We copy only SZ_SG_IO_HDR bytes, so that
would, strictly speaking, loosen the check.  However, for call chains via
->write() the caller has actually checked the entire range and SG_IO passes
exactly SZ_SG_IO_HDR for count.  So no visible behaviour changes happen if
we check only what we really need for copyin.

Link: https://lore.kernel.org/r/20191017193925.25539-5-viro@ZenIV.linux.org.uk


Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

parent c35a5cfb

drivers/scsi/sg.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -717,8 +717,6 @@ sg_new_write(Sg_fd sfp, struct file file, const char __user *buf,

		if (count < SZ_SG_IO_HDR)
		return -EINVAL;
		if (!access_ok(buf, count))
		return -EFAULT; /* protects following copy_from_user()s + get_user()s */

		sfp->cmd_q = 1; /* when sg_io_hdr seen, set command queuing on */
		if (!(srp = sg_add_request(sfp))) {
		@@ -728,7 +726,7 @@ sg_new_write(Sg_fd sfp, struct file file, const char __user *buf,
		}
		srp->sg_io_owned = sg_io_owned;
		hp = &srp->header;
		if (__copy_from_user(hp, buf, SZ_SG_IO_HDR)) {
		if (copy_from_user(hp, buf, SZ_SG_IO_HDR)) {
		sg_remove_request(sfp, srp);
		return -EFAULT;
		}

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