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mm: set S_SWAPFILE on blockdev swap devices

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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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong 2019-08-20 07:55:16 -07:00
parent 609488bc97
commit 1638045c36
1 changed files with 15 additions and 16 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

19
mm/swapfile.c
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@ -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);
}
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;
return 0;
}
@ -3295,7 +3295,6 @@ 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;
error = 0;
goto out;
@ -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();