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authorDomenico Andreoli <domenico.andreoli@linux.com>2020-05-19 20:14:10 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2020-05-27 17:55:59 +0200
commitad1e4f74c072eaa2c6d77dd710db31aafecd614f (patch)
treede6773b7d4489318ce9b6547d8368d8b114256b1 /kernel/power
parentc4f39a6c74389fcc93ac39056ef342f32ab57a23 (diff)
PM: hibernate: Restrict writes to the resume device
Hibernation via snapshot device requires write permission to the swap block device, the one that more often (but not necessarily) is used to store the hibernation image. With this patch, such permissions are granted iff: 1) snapshot device config option is enabled 2) swap partition is used as resume device In other circumstances the swap device is not writable from userspace. In order to achieve this, every write attempt to a swap device is checked against the device configured as part of the uswsusp API [0] using a pointer to the inode struct in memory. If the swap device being written was not configured for resuming, the write request is denied. NOTE: this implementation works only for swap block devices, where the inode configured by swapon (which sets S_SWAPFILE) is the same used by SNAPSHOT_SET_SWAP_AREA. In case of swap file, SNAPSHOT_SET_SWAP_AREA indeed receives the inode of the block device containing the filesystem where the swap file is located (+ offset in it) which is never passed to swapon and then has not set S_SWAPFILE. As result, the swap file itself (as a file) has never an option to be written from userspace. Instead it remains writable if accessed directly from the containing block device, which is always writeable from root. [0] Documentation/power/userland-swsusp.rst v2: - rename is_hibernate_snapshot_dev() to is_hibernate_resume_dev() - fix description so to correctly refer to the resume device Signed-off-by: Domenico Andreoli <domenico.andreoli@linux.com> Acked-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'kernel/power')
-rw-r--r--kernel/power/user.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 98548d1cf8a6..d5eedc2baa2a 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -35,8 +35,14 @@ static struct snapshot_data {
bool ready;
bool platform_support;
bool free_bitmaps;
+ struct inode *bd_inode;
} snapshot_state;
+int is_hibernate_resume_dev(const struct inode *bd_inode)
+{
+ return hibernation_available() && snapshot_state.bd_inode == bd_inode;
+}
+
static int snapshot_open(struct inode *inode, struct file *filp)
{
struct snapshot_data *data;
@@ -95,6 +101,7 @@ static int snapshot_open(struct inode *inode, struct file *filp)
data->frozen = false;
data->ready = false;
data->platform_support = false;
+ data->bd_inode = NULL;
Unlock:
unlock_system_sleep();
@@ -110,6 +117,7 @@ static int snapshot_release(struct inode *inode, struct file *filp)
swsusp_free();
data = filp->private_data;
+ data->bd_inode = NULL;
free_all_swap_pages(data->swap);
if (data->frozen) {
pm_restore_gfp_mask();
@@ -202,6 +210,7 @@ struct compat_resume_swap_area {
static int snapshot_set_swap_area(struct snapshot_data *data,
void __user *argp)
{
+ struct block_device *bdev;
sector_t offset;
dev_t swdev;
@@ -232,9 +241,12 @@ static int snapshot_set_swap_area(struct snapshot_data *data,
data->swap = -1;
return -EINVAL;
}
- data->swap = swap_type_of(swdev, offset, NULL);
+ data->swap = swap_type_of(swdev, offset, &bdev);
if (data->swap < 0)
return -ENODEV;
+
+ data->bd_inode = bdev->bd_inode;
+ bdput(bdev);
return 0;
}