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Message-ID: <156174691783.1557844.3238867236650883424.stgit@magnolia>
Date: Fri, 28 Jun 2019 11:35:17 -0700
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: hch@...radead.org, akpm@...ux-foundation.org, tytso@....edu,
viro@...iv.linux.org.uk, darrick.wong@...cle.com
Cc: linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 1/2] mm: set S_SWAPFILE on blockdev swap devices
From: Darrick J. Wong <darrick.wong@...cle.com>
Set S_SWAPFILE on block device inodes so that they have the same
protections as a swap flie.
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
mm/swapfile.c | 31 +++++++++++++++----------------
1 file changed, 15 insertions(+), 16 deletions(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 596ac98051c5..fa4edd0cca3a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2284,9 +2284,8 @@ EXPORT_SYMBOL_GPL(add_swap_extent);
* requirements, they are simply tossed out - we will never use those blocks
* for swapping.
*
- * For S_ISREG swapfiles we set S_SWAPFILE across the life of the swapon. This
- * prevents root from shooting her foot off by ftruncating an in-use swapfile,
- * which will scribble on the fs.
+ * For all swap devices we set S_SWAPFILE across the life of the swapon. This
+ * prevents users from writing to the swap device, which will corrupt memory.
*
* The amount of disk space which a single swap extent represents varies.
* Typically it is in the 1-4 megabyte range. So we can have hundreds of
@@ -2551,13 +2550,14 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
inode = mapping->host;
if (S_ISBLK(inode->i_mode)) {
struct block_device *bdev = I_BDEV(inode);
+
set_blocksize(bdev, old_block_size);
blkdev_put(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
- } else {
- inode_lock(inode);
- inode->i_flags &= ~S_SWAPFILE;
- inode_unlock(inode);
}
+
+ inode_lock(inode);
+ inode->i_flags &= ~S_SWAPFILE;
+ inode_unlock(inode);
filp_close(swap_file, NULL);
/*
@@ -2780,11 +2780,11 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
p->flags |= SWP_BLKDEV;
} else if (S_ISREG(inode->i_mode)) {
p->bdev = inode->i_sb->s_bdev;
- inode_lock(inode);
- if (IS_SWAPFILE(inode))
- return -EBUSY;
- } else
- return -EINVAL;
+ }
+
+ inode_lock(inode);
+ if (IS_SWAPFILE(inode))
+ return -EBUSY;
return 0;
}
@@ -3185,8 +3185,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
atomic_inc(&proc_poll_event);
wake_up_interruptible(&proc_poll_wait);
- if (S_ISREG(inode->i_mode))
- inode->i_flags |= S_SWAPFILE;
+ inode->i_flags |= S_SWAPFILE;
error = 0;
goto out;
bad_swap:
@@ -3208,7 +3207,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
if (inced_nr_rotate_swap)
atomic_dec(&nr_rotate_swap);
if (swap_file) {
- if (inode && S_ISREG(inode->i_mode)) {
+ if (inode) {
inode_unlock(inode);
inode = NULL;
}
@@ -3221,7 +3220,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
}
if (name)
putname(name);
- if (inode && S_ISREG(inode->i_mode))
+ if (inode)
inode_unlock(inode);
if (!error)
enable_swap_slots_cache();
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