| Message ID | 20170214180345.2074-1-jaegeuk@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 2017/2/15 2:03, Jaegeuk Kim wrote: > VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. > But, if there is a race condition, f2fs_add_link() can be called multiple > times, resulting in multiple dentries with a same name. This patches fixes > it by adding __f2fs_find_entry() in f2fs_add_link() path. As during ->lookup, i_mutex will be held all the time, so there is no race condition in between different file creators? Thanks, > > Cc: <stable@vger.kernel.org> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > fs/f2fs/dir.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > index 827c5daef4fc..bc7c48839bec 100644 > --- a/fs/f2fs/dir.c > +++ b/fs/f2fs/dir.c > @@ -643,14 +643,24 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, > struct inode *inode, nid_t ino, umode_t mode) > { > struct fscrypt_name fname; > + struct page *page; > + struct f2fs_dir_entry *de; > int err; > > err = fscrypt_setup_filename(dir, name, 0, &fname); > if (err) > return err; > > - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > - > + de = __f2fs_find_entry(dir, &fname, &page); > + if (de) { > + f2fs_dentry_kunmap(dir, page); > + f2fs_put_page(page, 0); > + err = -EEXIST; > + } else if (!IS_ERR(page)) { > + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > + } else { > + err = PTR_ERR(page); > + } > fscrypt_free_filename(&fname); > return err; > } >
On 02/15, Chao Yu wrote: > On 2017/2/15 2:03, Jaegeuk Kim wrote: > > VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. > > But, if there is a race condition, f2fs_add_link() can be called multiple > > times, resulting in multiple dentries with a same name. This patches fixes > > it by adding __f2fs_find_entry() in f2fs_add_link() path. > > As during ->lookup, i_mutex will be held all the time, so there is no race > condition in between different file creators? Hehe, yup. I dropped this patch. Thanks, > > Thanks, > > > > > Cc: <stable@vger.kernel.org> > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > > --- > > fs/f2fs/dir.c | 14 ++++++++++++-- > > 1 file changed, 12 insertions(+), 2 deletions(-) > > > > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c > > index 827c5daef4fc..bc7c48839bec 100644 > > --- a/fs/f2fs/dir.c > > +++ b/fs/f2fs/dir.c > > @@ -643,14 +643,24 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, > > struct inode *inode, nid_t ino, umode_t mode) > > { > > struct fscrypt_name fname; > > + struct page *page; > > + struct f2fs_dir_entry *de; > > int err; > > > > err = fscrypt_setup_filename(dir, name, 0, &fname); > > if (err) > > return err; > > > > - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > > - > > + de = __f2fs_find_entry(dir, &fname, &page); > > + if (de) { > > + f2fs_dentry_kunmap(dir, page); > > + f2fs_put_page(page, 0); > > + err = -EEXIST; > > + } else if (!IS_ERR(page)) { > > + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); > > + } else { > > + err = PTR_ERR(page); > > + } > > fscrypt_free_filename(&fname); > > return err; > > } > >
diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c index 827c5daef4fc..bc7c48839bec 100644 --- a/fs/f2fs/dir.c +++ b/fs/f2fs/dir.c @@ -643,14 +643,24 @@ int __f2fs_add_link(struct inode *dir, const struct qstr *name, struct inode *inode, nid_t ino, umode_t mode) { struct fscrypt_name fname; + struct page *page; + struct f2fs_dir_entry *de; int err; err = fscrypt_setup_filename(dir, name, 0, &fname); if (err) return err; - err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); - + de = __f2fs_find_entry(dir, &fname, &page); + if (de) { + f2fs_dentry_kunmap(dir, page); + f2fs_put_page(page, 0); + err = -EEXIST; + } else if (!IS_ERR(page)) { + err = __f2fs_do_add_link(dir, &fname, inode, ino, mode); + } else { + err = PTR_ERR(page); + } fscrypt_free_filename(&fname); return err; }
VFS uses f2fs_lookup() to decide f2fs_add_link() call during file creation. But, if there is a race condition, f2fs_add_link() can be called multiple times, resulting in multiple dentries with a same name. This patches fixes it by adding __f2fs_find_entry() in f2fs_add_link() path. Cc: <stable@vger.kernel.org> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> --- fs/f2fs/dir.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-)