The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From e40ff213898502d299351cc2fe1e350cd186f0d3 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o tytso@mit.edu Date: Sun, 1 Apr 2018 23:21:03 -0400 Subject: [PATCH] ext4: force revalidation of directory pointer after seekdir(2)
A malicious user could force the directory pointer to be in an invalid spot by using seekdir(2). Use the mechanism we already have to notice if the directory has changed since the last time we called ext4_readdir() to force a revalidation of the pointer.
Reported-by: syzbot+1236ce66f79263e8a862@syzkaller.appspotmail.com Signed-off-by: Theodore Ts'o tytso@mit.edu Cc: stable@vger.kernel.org
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c index da87cf757f7d..e2902d394f1b 100644 --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -365,13 +365,15 @@ static loff_t ext4_dir_llseek(struct file *file, loff_t offset, int whence) { struct inode *inode = file->f_mapping->host; int dx_dir = is_dx_dir(inode); - loff_t htree_max = ext4_get_htree_eof(file); + loff_t ret, htree_max = ext4_get_htree_eof(file);
if (likely(dx_dir)) - return generic_file_llseek_size(file, offset, whence, + ret = generic_file_llseek_size(file, offset, whence, htree_max, htree_max); else - return ext4_llseek(file, offset, whence); + ret = ext4_llseek(file, offset, whence); + file->f_version = inode_peek_iversion(inode) - 1; + return ret; }
/*