From 3dc87905fa8340ae8086229b208923194531bf8b Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Tue, 15 Oct 2013 06:33:10 +0000
Subject: [PATCH] Similar to debug.iosize_max_clamp sysctl, introduce
 devfs_iosize_max_clamp sysctl, which allows/disables SSIZE_MAX-sized i/o
 requests on the devfs files.

Sponsored by:	The FreeBSD Foundation
Reminded by:	Dmitry Sivachenko <trtrmitya@gmail.com>
MFC after:	1 week
---
 sys/fs/devfs/devfs_vnops.c | 4 ++++
 sys/kern/sys_generic.c     | 4 ++++
 sys/sys/systm.h            | 2 ++
 3 files changed, 10 insertions(+)

diff --git a/sys/fs/devfs/devfs_vnops.c b/sys/fs/devfs/devfs_vnops.c
index dcc10c877676..a05299a8e703 100644
--- a/sys/fs/devfs/devfs_vnops.c
+++ b/sys/fs/devfs/devfs_vnops.c
@@ -1178,6 +1178,8 @@ devfs_read_f(struct file *fp, struct uio *uio, struct ucred *cred,
 	struct cdevsw *dsw;
 	struct file *fpop;
 
+	if (uio->uio_resid > DEVFS_IOSIZE_MAX)
+		return (EINVAL);
 	fpop = td->td_fpop;
 	error = devfs_fp_check(fp, &dev, &dsw, &ref);
 	if (error)
@@ -1653,6 +1655,8 @@ devfs_write_f(struct file *fp, struct uio *uio, struct ucred *cred,
 	struct cdevsw *dsw;
 	struct file *fpop;
 
+	if (uio->uio_resid > DEVFS_IOSIZE_MAX)
+		return (EINVAL);
 	fpop = td->td_fpop;
 	error = devfs_fp_check(fp, &dev, &dsw, &ref);
 	if (error)
diff --git a/sys/kern/sys_generic.c b/sys/kern/sys_generic.c
index d4d6293034ab..13ccb585f580 100644
--- a/sys/kern/sys_generic.c
+++ b/sys/kern/sys_generic.c
@@ -78,6 +78,10 @@ __FBSDID("$FreeBSD$");
 int iosize_max_clamp = 1;
 SYSCTL_INT(_debug, OID_AUTO, iosize_max_clamp, CTLFLAG_RW,
     &iosize_max_clamp, 0, "Clamp max i/o size to INT_MAX");
+int devfs_iosize_max_clamp = 1;
+SYSCTL_INT(_debug, OID_AUTO, devfs_iosize_max_clamp, CTLFLAG_RW,
+    &devfs_iosize_max_clamp, 0, "Clamp max i/o size to INT_MAX for devices");
+
 /*
  * Assert that the return value of read(2) and write(2) syscalls fits
  * into a register.  If not, an architecture will need to provide the
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
index 2000e92a9dd3..b86f7a2357bd 100644
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -146,7 +146,9 @@ extern const void *zero_region;	/* address space maps to a zeroed page	*/
 
 extern int unmapped_buf_allowed;
 extern int iosize_max_clamp;
+extern int devfs_iosize_max_clamp;
 #define	IOSIZE_MAX	(iosize_max_clamp ? INT_MAX : SSIZE_MAX)
+#define	DEVFS_IOSIZE_MAX	(devfs_iosize_max_clamp ? INT_MAX : SSIZE_MAX)
 
 /*
  * General function declarations.