From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: hch@infradead.org, akpm@linux-foundation.org, tytso@mit.edu,
viro@zeniv.linux.org.uk
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v2 2/2] vfs: don't allow writes to swap files
Date: Fri, 16 Aug 2019 09:19:49 -0700 [thread overview]
Message-ID: <20190816161948.GJ15186@magnolia> (raw)
In-Reply-To: <156588515613.111054.13578448017133006248.stgit@magnolia>
From: Darrick J. Wong <darrick.wong@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.wong@oracle.com>
---
v2: add missing inode_drain_writes
---
fs/block_dev.c | 3 +++
include/linux/fs.h | 11 +++++++++++
mm/filemap.c | 3 +++
mm/memory.c | 4 ++++
mm/mmap.c | 8 ++++++--
mm/swapfile.c | 12 +++++++++++-
6 files changed, 38 insertions(+), 3 deletions(-)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index c2a85b587922..d9bab63a9b81 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1978,6 +1978,9 @@ 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/include/linux/fs.h b/include/linux/fs.h
index 56b8e358af5c..a2e3d446ba8e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3547,4 +3547,15 @@ 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 */
diff --git a/mm/filemap.c b/mm/filemap.c
index f93c58dde9c8..89bcdde903a3 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2989,6 +2989,9 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from)
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 e2bb51b6242e..b1dff75640b7 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2196,6 +2196,10 @@ 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;
diff --git a/mm/mmap.c b/mm/mmap.c
index 7e8c3e8ae75f..6bc21fca20bc 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1483,8 +1483,12 @@ 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))
- 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 a53b7c49b40e..dab43523afdd 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3275,6 +3275,17 @@ 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)
@@ -3295,7 +3306,6 @@ 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:
next prev parent reply other threads:[~2019-08-16 16:22 UTC|newest]
Thread overview: 12+ 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 ` [PATCH 1/2] mm: set S_SWAPFILE on blockdev swap devices Darrick J. Wong
2019-08-16 6:39 ` 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 ` Darrick J. Wong [this message]
2019-08-18 8:39 ` [PATCH v2 " 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
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