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fuse: truncate pagecache on atomic_o_trunc 

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: e4648309b8 ("fuse: truncate pending writes on O_TRUNC")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Miklos Szeredi 2021-08-17 21:05:16 +02:00
parent 5d5b74aa9c
commit 76224355db
1 changed files with 5 additions and 2 deletions
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7
fs/fuse/file.c
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@ -198,12 +198,11 @@ void fuse_finish_open(struct inode *inode, struct file *file)
struct fuse_file *ff = file->private_data; struct fuse_file *ff = file->private_data;
struct fuse_conn *fc = get_fuse_conn(inode); 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) if (ff->open_flags & FOPEN_STREAM)
stream_open(inode, file); stream_open(inode, file);
else if (ff->open_flags & FOPEN_NONSEEKABLE) else if (ff->open_flags & FOPEN_NONSEEKABLE)
nonseekable_open(inode, file); nonseekable_open(inode, file);
if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) { if (fc->atomic_o_trunc && (file->f_flags & O_TRUNC)) {
struct fuse_inode *fi = get_fuse_inode(inode); struct fuse_inode *fi = get_fuse_inode(inode);
@ -211,10 +210,14 @@ void fuse_finish_open(struct inode *inode, struct file *file)
fi->attr_version = atomic64_inc_return(&fc->attr_version); fi->attr_version = atomic64_inc_return(&fc->attr_version);
i_size_write(inode, 0); i_size_write(inode, 0);
spin_unlock(&fi->lock); spin_unlock(&fi->lock);
truncate_pagecache(inode, 0);
fuse_invalidate_attr(inode); fuse_invalidate_attr(inode);
if (fc->writeback_cache) if (fc->writeback_cache)
file_update_time(file); 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) if ((file->f_mode & FMODE_WRITE) && fc->writeback_cache)
fuse_link_write_file(file); fuse_link_write_file(file);
} }