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: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/block_dev.c b/fs/block_dev.c
index c2a85b5..d9bab63 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1978,6 +1978,9 @@
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/include/linux/fs.h b/include/linux/fs.h
index 56b8e35..a2e3d44 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3547,4 +3547,15 @@
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 */
diff --git a/mm/filemap.c b/mm/filemap.c
index d0cf700..40667c2 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2988,6 +2988,9 @@
loff_t count;
int ret;
+ if (IS_SWAPFILE(inode))
+ return -ETXTBSY;
+
if (!iov_iter_count(from))
return 0;
diff --git a/mm/memory.c b/mm/memory.c
index e2bb51b..b1dff75 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2196,6 +2196,10 @@
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;
diff --git a/mm/mmap.c b/mm/mmap.c
index 7e8c3e8a..6bc21fca 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1483,8 +1483,12 @@
case MAP_SHARED_VALIDATE:
if (flags & ~flags_mask)
return -EOPNOTSUPP;
- if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
- return -EACCES;
+ 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
diff --git a/mm/swapfile.c b/mm/swapfile.c
index a53b7c4..dab4352 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3275,6 +3275,17 @@
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)
@@ -3295,7 +3306,6 @@
atomic_inc(&proc_poll_event);
wake_up_interruptible(&proc_poll_wait);
- inode->i_flags |= S_SWAPFILE;
error = 0;
goto out;
bad_swap:
