2b46b108b6e4c702a881e59c2d5b1e76e710ae6297260b7227c4896d.patch

From a69580ee0337edfba02bd0234714c96c1e9c84c4 Mon Sep 17 00:00:00 2001
From: Will Drewry <wad@chromium.org>
Date: Thu, 21 Mar 2013 17:00:53 -0500
Subject: [PATCH] CHROMIUM: Restrict swapon() to "zram" devices / lock down
 zram
MIME-Version: 1.0
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This cl contains three distinct changes collapsed into
one CL as per semenzato's request:
1. Restrict CONFIG_SWAP to ensure that only zram devices
   may be used.
2. Restrict zram to disallow open calls, even from root, if
   the device is claimed (e.g., by sys_swapon)
3. Add swapoff fallback when filp_open fails to use the path lookup.
   I don't believe swapoff needs filp_open() since kern_path()
   provides the data needed without a file object.
4. Add an open counter to zram to ensure that it is not opened more
   times than swapon(2) will claim it -- twice:
   - blkdev_get and filp_open (for swap_file)

Signed-off-by: Will Drewry <wad@chromium.org>
TEST=tested on lumpy; swapon, swapoff, change zram during swapon fails, change withotu swapon succeeds.
BUG=chromium:220974

Change-Id: Ic281a7004a81b2897cf0bf1c5d334351061261f1
[sonnyrao: 3.8: fixup conflicts]
Reviewed-on: https://gerrit.chromium.org/gerrit/46168
Tested-by: Will Drewry <wad@chromium.org>
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
Commit-Queue: Will Drewry <wad@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/58780
Commit-Queue: Sonny Rao <sonnyrao@chromium.org>
Reviewed-by: Sonny Rao <sonnyrao@chromium.org>
Tested-by: Sonny Rao <sonnyrao@chromium.org>

[benzh: 3.14 rebase. Squashed a compilation error fix. Also zram driver moved
from drivers/staging/ to drivers/block/ in upstream]
Signed-off-by: Ben Zhang <benzh@chromium.org>

[rebase44(filbranden): Adapted the patch to merge our zram_open with the
 one introduced upstream (between v3.18 and v4.4).
 Squashed these three commits together:
 - CHROMIUM: Restrict swapon() to "zram" devices / lock down zram
 - CHROMIUM: Allow disk-based swap files
 - CHROMIUM: minor changes to chromium specific open.
]
Signed-off-by: Filipe Brandenburger <filbranden@chromium.org>

Conflicts:
        drivers/block/zram/zram_drv.h
        kernel/sysctl.c

[rebase412(groeck): Resolved conflicts]
Signed-off-by: Guenter Roeck <groeck@chromium.org>

[rebase419(groeck):
    Squashed commit:
        CHROMIUM: Fix mismatched mutex_unlock in swapon()
    Resolved context conflicts]
Signed-off-by: Guenter Roeck <groeck@chromium.org>

[rebase54(yuzhao):
	Restrict access to zram block device by bd_opener. This
	eliminates the need of an atomic counter and achieves both
	2 & 4; therefore there is no need to check bd_holder.]
Signed-off-by: Yu Zhao <yuzhao@google.com>
[rebase510(groeck): Resolved conflicts]
Signed-off-by: Guenter Roeck <groeck@chromium.org>

[rebase515(groeck)
    Squash:
	FIXUP: CHROMIUM: Restrict swapon() to "zram" devices / lock down zram
]

Create fixup.

Signed-off-by: Łukasz Bartosik <ukaszb@google.com>
Change-Id: I2cd096c1def691bdd72d8d2ed921210876662989
---
 drivers/block/zram/zram_drv.c | 10 ++++++++++
 include/linux/mm.h            |  2 ++
 init/Kconfig                  |  9 +++++++++
 kernel/sysctl.c               | 11 +++++++++++
 mm/swapfile.c                 | 35 ++++++++++++++++++++++++++++++-----
 5 files changed, 62 insertions(+), 5 deletions(-)

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 966aab902d19a6c1a4720fc78138761e267b23af..18718e8e3691cf78da23a2b9a642bf190f9ae54a 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1829,6 +1829,16 @@ static int zram_open(struct block_device *bdev, fmode_t mode)
 
 	WARN_ON(!mutex_is_locked(&bdev->bd_disk->open_mutex));
 
+	/*
+	 * Chromium OS specific behavior:
+	 * sys_swapon opens the device once to populate its swapinfo->swap_file
+	 * and once when it claims the block device (blkdev_get).  By limiting
+	 * the maximum number of opens to 2, we ensure there are no prior open
+	 * references before swap is enabled.
+	 */
+	if (bdev->bd_openers > 1)
+		return -EBUSY;
+
 	zram = bdev->bd_disk->private_data;
 	/* zram was claimed to reset so open request fails */
 	if (zram->claim)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8bbcccbc55654341c4d2b361549e1da4da6d65cb..0e8615f16052de5ebcb3176a08de133c64bebe38 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -204,6 +204,8 @@ extern int sysctl_overcommit_memory;
 extern int sysctl_overcommit_ratio;
 extern unsigned long sysctl_overcommit_kbytes;
 
+extern int sysctl_disk_based_swap;
+
 int overcommit_ratio_handler(struct ctl_table *, int, void *, size_t *,
 		loff_t *);
 int overcommit_kbytes_handler(struct ctl_table *, int, void *, size_t *,
diff --git a/init/Kconfig b/init/Kconfig
index 07f6958154d4db5b8fb564c356a6051aa035d287..cec06fdbb26f5c35c62eff43c10bad156cc48499 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -366,6 +366,15 @@ config DEFAULT_HOSTNAME
 	  but you may wish to use a different default here to make a minimal
 	  system more usable with less configuration.
 
+config DISK_BASED_SWAP
+	bool "Allow disk-based swap files in Chromium OS kernels"
+	depends on SWAP
+	default n
+	help
+	  By default, the Chromium OS kernel allows swapping only to
+	  zram devices. This option allows you to use disk-based files
+	  as swap devices too.  If unsure say N.
+
 config SYSVIPC
 	bool "System V IPC"
 	help
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 188c305aeb8b7fd8984721122dcfe11bd658aeaa..4cf0086fd90e75d4827ac04832f6b821bbe71706 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2462,6 +2462,17 @@ static struct ctl_table vm_table[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_ONE,
 	},
+#endif
+#ifdef CONFIG_DISK_BASED_SWAP
+	{
+		.procname	= "disk_based_swap",
+		.data		= &sysctl_disk_based_swap,
+		.maxlen		= sizeof(sysctl_disk_based_swap),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
 #endif
 	{ }
 };
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 5fc1237a9f214d45a30984ea45a842f8e62d522b..65ff59d58dc9aa58fa940221c06e93dc077ff17e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2390,6 +2390,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	struct filename *pathname;
 	int err, found = 0;
 	unsigned int old_block_size;
+	struct path path_holder;
+	struct path *victim_path = NULL;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -2402,10 +2404,16 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 
 	victim = file_open_name(pathname, O_RDWR|O_LARGEFILE, 0);
 	err = PTR_ERR(victim);
-	if (IS_ERR(victim))
-		goto out;
-
-	mapping = victim->f_mapping;
+	if (IS_ERR(victim)) {
+		/* Fallback to just the inode mapping if possible. */
+		if (kern_path(pathname->name, LOOKUP_FOLLOW, &path_holder))
+			goto out;  /* Propogate the original err. */
+		victim_path = &path_holder;
+		mapping = victim_path->dentry->d_inode->i_mapping;
+		victim = NULL;
+	} else {
+		mapping = victim->f_mapping;
+	}
 	spin_lock(&swap_lock);
 	plist_for_each_entry(p, &swap_active_head, list) {
 		if (p->flags & SWP_WRITEOK) {
@@ -2553,7 +2561,10 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	wake_up_interruptible(&proc_poll_wait);
 
 out_dput:
-	filp_close(victim, NULL);
+	if (victim)
+		filp_close(victim, NULL);
+	if (victim_path)
+		path_put(victim_path);
 out:
 	putname(pathname);
 	return err;
@@ -2756,11 +2767,17 @@ static struct swap_info_struct *alloc_swap_info(void)
 	return p;
 }
 
+/* This sysctl is only exposed when CONFIG_DISK_BASED_SWAP is enabled. */
+int sysctl_disk_based_swap;
+
 static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
 {
 	int error;
 
+	/* On Chromium OS, we only support zram swap devices. */
 	if (S_ISBLK(inode->i_mode)) {
+		char name[BDEVNAME_SIZE];
+
 		p->bdev = blkdev_get_by_dev(inode->i_rdev,
 				   FMODE_READ | FMODE_WRITE | FMODE_EXCL, p);
 		if (IS_ERR(p->bdev)) {
@@ -2768,6 +2785,12 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
 			p->bdev = NULL;
 			return error;
 		}
+		bdevname(p->bdev, name);
+		if (strncmp(name, "zram", strlen("zram"))) {
+			iput(p->bdev->bd_inode);
+			p->bdev = NULL;
+			return -EINVAL;
+		}
 		p->old_block_size = block_size(p->bdev);
 		error = set_blocksize(p->bdev, PAGE_SIZE);
 		if (error < 0)
@@ -2781,6 +2804,8 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
 			return -EINVAL;
 		p->flags |= SWP_BLKDEV;
 	} else if (S_ISREG(inode->i_mode)) {
+		if (!sysctl_disk_based_swap)
+			return -EINVAL;
 		p->bdev = inode->i_sb->s_bdev;
 	}
 
-- 
2.38.1.584.g0f3c55d4c2-goog