fuse: fix bad inode

commit 5d069dbe8aaf2a197142558b6fb2978189ba3454 upstream.

Jan Kara's analysis of the syzbot report (edited):

  The reproducer opens a directory on FUSE filesystem, it then attaches
  dnotify mark to the open directory.  After that a fuse_do_getattr() call
  finds that attributes returned by the server are inconsistent, and calls
  make_bad_inode() which, among other things does:

          inode->i_mode = S_IFREG;

  This then confuses dnotify which doesn't tear down its structures
  properly and eventually crashes.

Avoid calling make_bad_inode() on a live inode: switch to a private flag on
the fuse inode.  Also add the test to ops which the bad_inode_ops would
have caught.

This bug goes back to the initial merge of fuse in 2.6.14...

Reported-by: syzbot+f427adf9324b92652ccc@syzkaller.appspotmail.com
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Tested-by: Jan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
[bwh: Backported to 4.19:
 - Drop changes in fuse_dir_fsync(), fuse_readahead(), fuse_evict_inode()
 - In fuse_get_link(), return ERR_PTR(-EIO) for bad inodes
 - Convert some additional calls to is_bad_inode()
 - Adjust filename, context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 18 insertions, 9 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 13371a40f7a1..ed9b3ebc0cca 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -210,6 +210,9 @@ int fuse_open_common(struct inode *inode, struct file *file, bool isdir)
 			  fc->atomic_o_trunc &&
 			  fc->writeback_cache;
 
+	if (fuse_is_bad(inode))
+		return -EIO;
+
 	err = generic_file_open(inode, file);
 	if (err)
 		return err;
@@ -411,7 +414,7 @@ static int fuse_flush(struct file *file, fl_owner_t id)
 	struct fuse_flush_in inarg;
 	int err;
 
-	if (is_bad_inode(inode))
+	if (fuse_is_bad(inode))
 		return -EIO;
 
 	if (fc->no_flush)
@@ -459,7 +462,7 @@ int fuse_fsync_common(struct file *file, loff_t start, loff_t end,
 	struct fuse_fsync_in inarg;
 	int err;
 
-	if (is_bad_inode(inode))
+	if (fuse_is_bad(inode))
 		return -EIO;
 
 	inode_lock(inode);
@@ -774,7 +777,7 @@ static int fuse_readpage(struct file *file, struct page *page)
 	int err;
 
 	err = -EIO;
-	if (is_bad_inode(inode))
+	if (fuse_is_bad(inode))
 		goto out;
 
 	err = fuse_do_readpage(file, page);
@@ -901,7 +904,7 @@ static int fuse_readpages(struct file *file, struct address_space *mapping,
 	int nr_alloc = min_t(unsigned, nr_pages, FUSE_MAX_PAGES_PER_REQ);
 
 	err = -EIO;
-	if (is_bad_inode(inode))
+	if (fuse_is_bad(inode))
 		goto out;
 
 	data.file = file;
@@ -931,6 +934,9 @@ static ssize_t fuse_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 	struct inode *inode = iocb->ki_filp->f_mapping->host;
 	struct fuse_conn *fc = get_fuse_conn(inode);
 
+	if (fuse_is_bad(inode))
+		return -EIO;
+
 	/*
 	 * In auto invalidate mode, always update attributes on read.
 	 * Otherwise, only update if we attempt to read past EOF (to ensure
@@ -1131,7 +1137,7 @@ static ssize_t fuse_perform_write(struct kiocb *iocb,
 	int err = 0;
 	ssize_t res = 0;
 
-	if (is_bad_inode(inode))
+	if (fuse_is_bad(inode))
 		return -EIO;
 
 	if (inode->i_size < pos + iov_iter_count(ii))
@@ -1188,6 +1194,9 @@ static ssize_t fuse_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	ssize_t err;
 	loff_t endbyte = 0;
 
+	if (fuse_is_bad(inode))
+		return -EIO;
+
 	if (get_fuse_conn(inode)->writeback_cache) {
 		/* Update size (EOF optimization) and mode (SUID clearing) */
 		err = fuse_update_attributes(mapping->host, file);
@@ -1424,7 +1433,7 @@ static ssize_t __fuse_direct_read(struct fuse_io_priv *io,
 	ssize_t res;
 	struct inode *inode = file_inode(io->iocb->ki_filp);
 
-	if (is_bad_inode(inode))
+	if (fuse_is_bad(inode))
 		return -EIO;
 
 	res = fuse_direct_io(io, iter, ppos, 0);
@@ -1446,7 +1455,7 @@ static ssize_t fuse_direct_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	struct fuse_io_priv io = FUSE_IO_PRIV_SYNC(iocb);
 	ssize_t res;
 
-	if (is_bad_inode(inode))
+	if (fuse_is_bad(inode))
 		return -EIO;
 
 	/* Don't allow parallel writes to the same file */
@@ -1920,7 +1929,7 @@ static int fuse_writepages(struct address_space *mapping,
 	int err;
 
 	err = -EIO;
-	if (is_bad_inode(inode))
+	if (fuse_is_bad(inode))
 		goto out;
 
 	data.inode = inode;
@@ -2705,7 +2714,7 @@ long fuse_ioctl_common(struct file *file, unsigned int cmd,
 	if (!fuse_allow_current_process(fc))
 		return -EACCES;
 
-	if (is_bad_inode(inode))
+	if (fuse_is_bad(inode))
 		return -EIO;
 
 	return fuse_do_ioctl(file, cmd, arg, flags);