From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eiichi Tsukata Date: Wed, 21 Nov 2018 11:44:00 +0900 Subject: [Cluster-devel] [PATCH v1 4/4] overlayfs: fix race between llseek SEEK_END and write In-Reply-To: <20181121024400.4346-1-devel@etsukata.com> References: <20181121024400.4346-1-devel@etsukata.com> Message-ID: <20181121024400.4346-5-devel@etsukata.com> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Implement individual lock for SEEK_END for overlayfs which directly calls generic_file_llseek_size(). Signed-off-by: Eiichi Tsukata --- fs/overlayfs/file.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-) diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index 84dd957efa24..57bc6538eea8 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -146,10 +146,27 @@ static int ovl_release(struct inode *inode, struct file *file) static loff_t ovl_llseek(struct file *file, loff_t offset, int whence) { struct inode *realinode = ovl_inode_real(file_inode(file)); + loff_t ret; - return generic_file_llseek_size(file, offset, whence, - realinode->i_sb->s_maxbytes, - i_size_read(realinode)); + switch (whence) { + default: + return generic_file_llseek_size(file, offset, whence, + realinode->i_sb->s_maxbytes, + i_size_read(realinode)); + case SEEK_END: + case SEEK_DATA: + case SEEK_HOLE: + /* + * protects against inode size race with write so that llseek + * doesn't see inode size being updated in individual fs write + */ + inode_lock(realinode); + ret = generic_file_llseek_size(file, offset, whence, + realinode->i_sb->s_maxbytes, + i_size_read(realinode)); + inode_unlock(realinode); + return ret; + } } static void ovl_file_accessed(struct file *file) -- 2.19.1