Linux-Fsdevel Archive on lore.kernel.org
 help / color / Atom feed
From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: hch@infradead.org, akpm@linux-foundation.org, tytso@mit.edu,
	viro@zeniv.linux.org.uk, darrick.wong@oracle.com
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH 1/2] mm: set S_SWAPFILE on blockdev swap devices
Date: Thu, 15 Aug 2019 09:05:47 -0700
Message-ID: <156588514761.111054.15427341787826850860.stgit@magnolia> (raw)
In-Reply-To: <156588514105.111054.13645634739408399209.stgit@magnolia>

From: Darrick J. Wong <darrick.wong@oracle.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@oracle.com>
---
 mm/swapfile.c |   31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)


diff --git a/mm/swapfile.c b/mm/swapfile.c
index 0789a762ce2f..a53b7c49b40e 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2368,9 +2368,8 @@ 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
@@ -2661,13 +2660,14 @@ 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);
 
 	/*
@@ -2890,11 +2890,11 @@ 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;
 }
@@ -3295,8 +3295,7 @@ 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:
@@ -3318,7 +3317,7 @@ 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;
 		}
@@ -3331,7 +3330,7 @@ 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();


  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-15 16:05 [PATCH v3 0/2] vfs: make active swap files unwritable Darrick J. Wong
2019-08-15 16:05 ` Darrick J. Wong [this message]
2019-08-16  6:39   ` [PATCH 1/2] mm: set S_SWAPFILE on blockdev swap devices Christoph Hellwig
2019-08-15 16:05 ` [PATCH 2/2] vfs: don't allow writes to swap files Darrick J. Wong
2019-08-16  6:41   ` Christoph Hellwig
2019-08-16  6:48     ` Darrick J. Wong
2019-08-16 16:19   ` [PATCH v2 " Darrick J. Wong
2019-08-18  8:39     ` Christoph Hellwig
2019-08-15 16:34 ` [PATCH RFC 3/2] fstests: check that we can't write " Darrick J. Wong
2019-08-15 21:26   ` Andrew Morton
2019-08-16  2:13     ` Darrick J. Wong
2019-08-17  2:05   ` [PATCH v2 " Darrick J. Wong
  -- strict thread matches above, loose matches on Subject: below --
2019-06-28 18:35 [PATCH v2 0/2] vfs: make active swap files unwritable Darrick J. Wong
2019-06-28 18:35 ` [PATCH 1/2] mm: set S_SWAPFILE on blockdev swap devices Darrick J. Wong

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=156588514761.111054.15427341787826850860.stgit@magnolia \
    --to=darrick.wong@oracle.com \
    --cc=akpm@linux-foundation.org \
    --cc=hch@infradead.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-xfs@vger.kernel.org \
    --cc=tytso@mit.edu \
    --cc=viro@zeniv.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Fsdevel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-fsdevel/0 linux-fsdevel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-fsdevel linux-fsdevel/ https://lore.kernel.org/linux-fsdevel \
		linux-fsdevel@vger.kernel.org linux-fsdevel@archiver.kernel.org
	public-inbox-index linux-fsdevel


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-fsdevel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox