From: Darrick J. Wong <darrick.w...@oracle.com>
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: Darrick J. Wong <darrick.w...@oracle.com>
---
fs/attr.c | 16 ++++++++--------
fs/block_dev.c | 3 +++
mm/filemap.c | 3 +++
mm/memory.c | 3 ++-
mm/mmap.c | 2 ++
mm/swapfile.c | 12 +++++++++++-
6 files changed, 29 insertions(+), 10 deletions(-)
diff --git a/fs/attr.c b/fs/attr.c
index 1fcfdcc5b367..7480d5dd22c0 100644
--- a/fs/attr.c
+++ b/fs/attr.c
@@ -134,6 +134,14 @@ EXPORT_SYMBOL(setattr_prepare);
*/
int inode_newsize_ok(const struct inode *inode, loff_t offset)
{
+ /*
+ * Truncation of in-use swapfiles is disallowed - the kernel owns the
+ * disk space now. We must prevent subsequent swapout to scribble on
+ * the now-freed blocks.
+ */
+ if (IS_SWAPFILE(inode) && inode->i_size != offset)
+ return -ETXTBSY;
+
if (inode->i_size < offset) {
unsigned long limit;
@@ -142,14 +150,6 @@ int inode_newsize_ok(const struct inode *inode, loff_t
offset)
goto out_sig;
if (offset > inode->i_sb->s_maxbytes)
goto out_big;
- } else {
- /*
- * truncation of in-use swapfiles is disallowed - it would
- * cause subsequent swapout to scribble on the now-freed
- * blocks.
- */
- if (IS_SWAPFILE(inode))
- return -ETXTBSY;
}
return 0;
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 749f5984425d..f57d15e5338b 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1948,6 +1948,9 @@ 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;
diff --git a/mm/filemap.c b/mm/filemap.c
index dad85e10f5f8..fd80bc20e30a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2938,6 +2938,9 @@ inline ssize_t generic_write_checks(struct kiocb *iocb,
struct iov_iter *from)
if (IS_IMMUTABLE(inode))
return -EPERM;
+ if (IS_SWAPFILE(inode))
+ return -ETXTBSY;
+
if (!iov_iter_count(from))
return 0;
diff --git a/mm/memory.c b/mm/memory.c
index abf795277f36..5acb5bb04e21 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2236,7 +2236,8 @@ 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_IMMUTABLE(vmf->vma->vm_file->f_mapping->host))
+ (IS_IMMUTABLE(vmf->vma->vm_file->f_mapping->host) ||
+ IS_SWAPFILE(vmf->vma->vm_file->f_mapping->host)))
return VM_FAULT_SIGBUS;
ret = vmf->vma->vm_ops->page_mkwrite(vmf);
diff --git a/mm/mmap.c b/mm/mmap.c
index b3ebca2702bf..1abe55822324 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1488,6 +1488,8 @@ unsigned long do_mmap(struct file *file, unsigned long
addr,
return -EACCES;
if (IS_IMMUTABLE(file->f_mapping->host))
return -EPERM;
+ if (IS_SWAPFILE(file->f_mapping->host))
+ return -ETXTBSY;
}
/*
diff --git a/mm/swapfile.c b/mm/swapfile.c
index fa4edd0cca3a..1fc820c71baf 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3165,6 +3165,17 @@ SYSCALL_DEFINE2(swapon, const char __user *,
specialfile, int, swap_flags)
if (error)
goto bad_swap;
+ /*
+ * Flush any pending IO and dirty mappings before we start using this
+ * swap device.
+ */
+ inode->i_flags |= S_SWAPFILE;
+ error = inode_drain_writes(inode);
+ if (error) {
+ inode->i_flags &= ~S_SWAPFILE;
+ goto bad_swap;
+ }
+
mutex_lock(&swapon_mutex);
prio = -1;
if (swap_flags & SWAP_FLAG_PREFER)
@@ -3185,7 +3196,6 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile,
int, swap_flags)
atomic_inc(&proc_poll_event);
wake_up_interruptible(&proc_poll_wait);
- inode->i_flags |= S_SWAPFILE;
error = 0;
goto out;
bad_swap:
