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fuse: fix fallocate vs. ftruncate race

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commit 0ab08f576b upstream.

A former patch introducing FUSE_I_SIZE_UNSTABLE flag provided detailed
description of races between ftruncate and anyone who can extend i_size:

> 1. As in the previous scenario fuse_dentry_revalidate() discovered that i_size
> changed (due to our own fuse_do_setattr()) and is going to call
> truncate_pagecache() for some  'new_size' it believes valid right now. But by
> the time that particular truncate_pagecache() is called ...
> 2. fuse_do_setattr() returns (either having called truncate_pagecache() or
> not -- it doesn't matter).
> 3. The file is extended either by write(2) or ftruncate(2) or fallocate(2).
> 4. mmap-ed write makes a page in the extended region dirty.

This patch adds necessary bits to fuse_file_fallocate() to protect from that
race.

Signed-off-by: Maxim Patlasov <mpatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Maxim Patlasov
2013-09-13 19:20:16 +04:00
committed by Greg Kroah-Hartman
parent eb12ca30f1
commit 9abd30b435
1 changed files with 7 additions and 0 deletions
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7
fs/fuse/file.c
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@@ -2468,6 +2468,7 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
{
struct fuse_file *ff = file->private_data;
struct inode *inode = file->f_inode;
struct fuse_inode *fi = get_fuse_inode(inode);
struct fuse_conn *fc = ff->fc;
struct fuse_req *req;
struct fuse_fallocate_in inarg = {
@@ -2496,6 +2497,9 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
}
}
if (!(mode & FALLOC_FL_KEEP_SIZE))
set_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
req = fuse_get_req_nopages(fc);
if (IS_ERR(req)) {
err = PTR_ERR(req);
@@ -2528,6 +2532,9 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset,
fuse_invalidate_attr(inode);
out:
if (!(mode & FALLOC_FL_KEEP_SIZE))
clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state);
if (lock_inode)
mutex_unlock(&inode->i_mutex);