3.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Maxim Patlasov <MPatlasov@xxxxxxxxxxxxx>
commit 0ab08f576b9e6a6b689fc6b4e632079b978e619b 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@xxxxxxxxxxxxx>
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/fuse/file.c | 7 +++++++
1 file changed, 7 insertions(+)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2468,6 +2468,7 @@ static long fuse_file_fallocate(struct f
{
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 f
}
}
+ 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 f
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);
--
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