DivestOS/Patches/Linux_CVEs/CVE-2017-0794/ANY/0001.patch

From 47b3a105cc4cec0d912345d27d9743b97691b21c Mon Sep 17 00:00:00 2001
From: Robb Glasser <rglasser@google.com>
Date: Fri, 24 Mar 2017 16:23:37 -0700
Subject: [PATCH] Prevent potential double frees in sg driver

sg_ioctl could be spammed by requests, leading to a double free in
__free_pages. This protects the entry points of sg_ioctl where the
memory could be corrupted by a double call to __free_pages if multiple
requests are happening concurrently.

Bug:35644812

Change-Id: Ie13f65beb6974430f90292e2742841b26aecb8b1
Signed-off-by: Robb Glasser <rglasser@google.com>
---
 drivers/scsi/sg.c | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 721d839d6c543..9a600f05ab57a 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -486,7 +486,7 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos)
 		old_hdr->result = EIO;
 		break;
 	case DID_ERROR:
-		old_hdr->result = (srp->sense_b[0] == 0 && 
+		old_hdr->result = (srp->sense_b[0] == 0 &&
 				  hp->masked_status == GOOD) ? 0 : EIO;
 		break;
 	default:
@@ -832,8 +832,10 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 			return -ENXIO;
 		if (!access_ok(VERIFY_WRITE, p, SZ_SG_IO_HDR))
 			return -EFAULT;
+		mutex_lock(&sfp->parentdp->open_rel_lock);
 		result = sg_new_write(sfp, filp, p, SZ_SG_IO_HDR,
 				 1, read_only, 1, &srp);
+		mutex_unlock(&sfp->parentdp->open_rel_lock);
 		if (result < 0)
 			return result;
 		result = wait_event_interruptible(sfp->read_wait,
@@ -873,8 +875,10 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 			sfp->low_dma = 1;
 			if ((0 == sfp->low_dma) && (0 == sg_res_in_use(sfp))) {
 				val = (int) sfp->reserve.bufflen;
+				mutex_lock(&sfp->parentdp->open_rel_lock);
 				sg_remove_scat(&sfp->reserve);
 				sg_build_reserve(sfp, val);
+				mutex_unlock(&sfp->parentdp->open_rel_lock);
 			}
 		} else {
 			if (sdp->detached)
@@ -942,15 +946,17 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 		result = get_user(val, ip);
 		if (result)
 			return result;
-                if (val < 0)
-                        return -EINVAL;
+		if (val < 0)
+			return -EINVAL;
 		val = min_t(int, val,
 			    queue_max_sectors(sdp->device->request_queue) * 512);
 		if (val != sfp->reserve.bufflen) {
 			if (sg_res_in_use(sfp) || sfp->mmap_called)
 				return -EBUSY;
+			mutex_lock(&sfp->parentdp->open_rel_lock);
 			sg_remove_scat(&sfp->reserve);
 			sg_build_reserve(sfp, val);
+			mutex_unlock(&sfp->parentdp->open_rel_lock);
 		}
 		return 0;
 	case SG_GET_RESERVED_SIZE:
@@ -1003,8 +1009,8 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 				if (srp) {
 					rinfo[val].req_state = srp->done + 1;
 					rinfo[val].problem =
-					    srp->header.masked_status & 
-					    srp->header.host_status & 
+					    srp->header.masked_status &
+					    srp->header.host_status &
 					    srp->header.driver_status;
 					if (srp->done)
 						rinfo[val].duration =
@@ -1025,7 +1031,7 @@ sg_ioctl(struct file *filp, unsigned int cmd_in, unsigned long arg)
 				}
 			}
 			read_unlock_irqrestore(&sfp->rq_list_lock, iflags);
-			result = __copy_to_user(p, rinfo, 
+			result = __copy_to_user(p, rinfo,
 						SZ_SG_REQ_INFO * SG_MAX_QUEUE);
 			result = result ? -EFAULT : 0;
 			kfree(rinfo);
@@ -1127,14 +1133,14 @@ static long sg_compat_ioctl(struct file *filp, unsigned int cmd_in, unsigned lon
 		return -ENXIO;
 
 	sdev = sdp->device;
-	if (sdev->host->hostt->compat_ioctl) { 
+	if (sdev->host->hostt->compat_ioctl) {
 		int ret;
 
 		ret = sdev->host->hostt->compat_ioctl(sdev, cmd_in, (void __user *)arg);
 
 		return ret;
 	}
-	
+
 	return -ENOIOCTLCMD;
 }
 #endif
@@ -1594,7 +1600,7 @@ init_sg(void)
 	else
 		def_reserved_size = sg_big_buff;
 
-	rc = register_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0), 
+	rc = register_chrdev_region(MKDEV(SCSI_GENERIC_MAJOR, 0),
 				    SG_MAX_DEVS, "sg");
 	if (rc)
 		return rc;
@@ -2234,7 +2240,7 @@ static const struct file_operations adio_fops = {
 };
 
 static int sg_proc_single_open_dressz(struct inode *inode, struct file *file);
-static ssize_t sg_proc_write_dressz(struct file *filp, 
+static ssize_t sg_proc_write_dressz(struct file *filp,
 		const char __user *buffer, size_t count, loff_t *off);
 static const struct file_operations dressz_fops = {
 	.owner = THIS_MODULE,
@@ -2374,7 +2380,7 @@ static int sg_proc_single_open_adio(struct inode *inode, struct file *file)
 	return single_open(file, sg_proc_seq_show_int, &sg_allow_dio);
 }
 
-static ssize_t 
+static ssize_t
 sg_proc_write_adio(struct file *filp, const char __user *buffer,
 		   size_t count, loff_t *off)
 {
@@ -2395,7 +2401,7 @@ static int sg_proc_single_open_dressz(struct inode *inode, struct file *file)
 	return single_open(file, sg_proc_seq_show_int, &sg_big_buff);
 }
 
-static ssize_t 
+static ssize_t
 sg_proc_write_dressz(struct file *filp, const char __user *buffer,
 		     size_t count, loff_t *off)
 {
@@ -2552,7 +2558,7 @@ static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
 			hp = &srp->header;
 			new_interface = (hp->interface_id == '\0') ? 0 : 1;
 			if (srp->res_used) {
-				if (new_interface && 
+				if (new_interface &&
 				    (SG_FLAG_MMAP_IO & hp->flags))
 					cp = "     mmap>> ";
 				else
@@ -2566,7 +2572,7 @@ static void sg_proc_debug_helper(struct seq_file *s, Sg_device * sdp)
 			seq_printf(s, cp);
 			blen = srp->data.bufflen;
 			usg = srp->data.k_use_sg;
-			seq_printf(s, srp->done ? 
+			seq_printf(s, srp->done ?
 				   ((1 == srp->done) ?  "rcv:" : "fin:")
 				   : "act:");
 			seq_printf(s, " id=%d blen=%d",