[PATCH AUTOSEL 5.6 050/129] hibernate: Allow uswsusp to write to swap

Sasha Levin
2020-04-15T13:10:16Z

From: Domenico Andreoli <domenico.andreoli@linux.com>

[ Upstream commit 56939e014a6c212b317414faa307029e2e80c3b9 ]

It turns out that there is one use case for programs being able to
write to swap devices, and that is the userspace hibernation code.

Quick fix: disable the S_SWAPFILE check if hibernation is configured.

Fixes: dc617f29dbe5 ("vfs: don't allow writes to swap files")
Reported-by: Domenico Andreoli <domenico.andreoli@linux.com>
Reported-by: Marian Klein <mkleinsoft@gmail.com>
Signed-off-by: Domenico Andreoli <domenico.andreoli@linux.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/block_dev.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 69bf2fb6f7cda..84fe0162ff13e 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -34,6 +34,7 @@
#include <linux/task_io_accounting_ops.h>
#include <linux/falloc.h>
#include <linux/uaccess.h>
+#include <linux/suspend.h>
#include "internal.h"

struct bdev_inode {
@@ -2001,7 +2002,8 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
if (bdev_read_only(I_BDEV(bd_inode)))
return -EPERM;

- if (IS_SWAPFILE(bd_inode))
+ /* uswsusp needs write permission to the swap */
+ if (IS_SWAPFILE(bd_inode) && !hibernation_available())
return -ETXTBSY;

if (!iov_iter_count(from))
--
2.20.1