[PATCH 5.10 230/236] fuse: truncate pagecache on atomic_o_trunc

Greg Kroah-Hartman
2021-09-13T13:50:30Z

From: Miklos Szeredi <mszeredi@redhat.com>

commit 76224355db7570cbe6b6f75c8929a1558828dd55 upstream.

fuse_finish_open() will be called with FUSE_NOWRITE in case of atomic
O_TRUNC. This can deadlock with fuse_wait_on_page_writeback() in
fuse_launder_page() triggered by invalidate_inode_pages2().

Fix by replacing invalidate_inode_pages2() in fuse_finish_open() with a
truncate_pagecache() call. This makes sense regardless of FOPEN_KEEP_CACHE
or fc->writeback cache, so do it unconditionally.

Reported-by: Xie Yongji <xieyongji@bytedance.com>
Reported-and-tested-by: syzbot+bea44a5189836d956894@syzkaller.appspotmail.com
Fixes: e4648309b85a ("fuse: truncate pending writes on O_TRUNC")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/fuse/file.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -194,12 +194,11 @@ void fuse_finish_open(struct inode *inod
struct fuse_file *ff = file->private_data;
struct fuse_conn *fc = get_fuse_conn(inode);

- if (!(ff->open_flags & FOPEN_KEEP_CACHE))
- invalidate_inode_pages2(inode->i_mapping);
if (ff->open_flags & FOPEN_STREAM)
stream_open(inode, file);
else if (ff->open_flags & FOPEN_NONSEEKABLE)
nonseekable_open(inode, file);
+
if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) {
struct fuse_inode *fi = get_fuse_inode(inode);

@@ -207,10 +206,14 @@ void fuse_finish_open(struct inode *inod
fi->attr_version = atomic64_inc_return(&fc->attr_version);
i_size_write(inode, 0);
spin_unlock(&fi->lock);
+ truncate_pagecache(inode, 0);
fuse_invalidate_attr(inode);
if (fc->writeback_cache)
file_update_time(file);
+ } else if (!(ff->open_flags & FOPEN_KEEP_CACHE)) {
+ invalidate_inode_pages2(inode->i_mapping);
}
+
if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
fuse_link_write_file(file);
}