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Commit 8cfd90e1 authored by Darrick J. Wong's avatar Darrick J. Wong Committed by Jaegeuk Kim
Browse files

vfs: don't allow writes to swap files 



Don't let userspace write to an active swap file because the kernel
effectively has a long term lease on the storage and things could get
seriously corrupted if we let this happen.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
parent a9f3d1d1

fs/block_dev.c

+3 −0
Original line number Diff line number Diff line
@@ -1901,6 +1901,9 @@ 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))

		return -ETXTBSY;



	if (!iov_iter_count(from))

		return 0;

include/linux/fs.h

+11 −0
Original line number Diff line number Diff line
@@ -3479,4 +3479,15 @@ static inline void simple_fill_fsxattr(struct fsxattr *fa, __u32 xflags) 
	fa->fsx_xflags = xflags;

}



/*

 * Flush file data before changing attributes.  Caller must hold any locks

 * required to prevent further writes to this file until we're done setting

 * flags.

 */

static inline int inode_drain_writes(struct inode *inode)

{

	inode_dio_wait(inode);

	return filemap_write_and_wait(inode->i_mapping);

}



#endif /* _LINUX_FS_H */

mm/filemap.c

+3 −0
Original line number Diff line number Diff line
@@ -2929,6 +2929,9 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) 
	unsigned long limit = rlimit(RLIMIT_FSIZE);

	loff_t pos;



	if (IS_SWAPFILE(inode))

		return -ETXTBSY;



	if (!iov_iter_count(from))

		return 0;

mm/memory.c

+4 −0
Original line number Diff line number Diff line
@@ -2385,6 +2385,10 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf) 


	vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;



	if (vmf->vma->vm_file &&

	    IS_SWAPFILE(vmf->vma->vm_file->f_mapping->host))

		return VM_FAULT_SIGBUS;



	ret = vmf->vma->vm_ops->page_mkwrite(vmf);

	/* Restore original flags so that caller is not surprised */

	vmf->flags = old_flags;

mm/mmap.c

+6 −2
Original line number Diff line number Diff line
@@ -1457,8 +1457,12 @@ unsigned long do_mmap(struct file *file, unsigned long addr, 
		case MAP_SHARED_VALIDATE:

			if (flags & ~flags_mask)

				return -EOPNOTSUPP;

			if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))

			if (prot & PROT_WRITE) {

				if (!(file->f_mode & FMODE_WRITE))

					return -EACCES;

				if (IS_SWAPFILE(file->f_mapping->host))

					return -ETXTBSY;

			}



			/*

			 * Make sure we don't allow writing to an append-only