From a9043a24c6e340d45b204d294a25044726fd2770 Mon Sep 17 00:00:00 2001 From: Ryusuke Konishi Date: Tue, 4 Oct 2022 00:05:19 +0900 Subject: [PATCH] nilfs2: fix use-after-free bug of struct nilfs_root commit d325dc6eb763c10f591c239550b8c7e5466a5d09 upstream. If the beginning of the inode bitmap area is corrupted on disk, an inode with the same inode number as the root inode can be allocated and fail soon after. In this case, the subsequent call to nilfs_clear_inode() on that bogus root inode will wrongly decrement the reference counter of struct nilfs_root, and this will erroneously free struct nilfs_root, causing kernel oopses. This fixes the problem by changing nilfs_new_inode() to skip reserved inode numbers while repairing the inode bitmap. Link: https://lkml.kernel.org/r/20221003150519.39789-1-konishi.ryusuke@gmail.com Signed-off-by: Ryusuke Konishi Reported-by: syzbot+b8c672b0e22615c80fe0@syzkaller.appspotmail.com Reported-by: Khalid Masum Tested-by: Ryusuke Konishi Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- fs/nilfs2/inode.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c index abfe9e2a2e43..3c9cd12dad91 100644 --- a/fs/nilfs2/inode.c +++ b/fs/nilfs2/inode.c @@ -344,6 +344,7 @@ struct inode *nilfs_new_inode(struct inode *dir, umode_t mode) struct inode *inode; struct nilfs_inode_info *ii; struct nilfs_root *root; + struct buffer_head *bh; int err = -ENOMEM; ino_t ino; @@ -359,11 +360,26 @@ struct inode *nilfs_new_inode(struct inode *dir, umode_t mode) ii->i_state = BIT(NILFS_I_NEW); ii->i_root = root; - err = nilfs_ifile_create_inode(root->ifile, &ino, &ii->i_bh); + err = nilfs_ifile_create_inode(root->ifile, &ino, &bh); if (unlikely(err)) goto failed_ifile_create_inode; /* reference count of i_bh inherits from nilfs_mdt_read_block() */ + if (unlikely(ino < NILFS_USER_INO)) { + nilfs_msg(sb, KERN_WARNING, + "inode bitmap is inconsistent for reserved inodes"); + do { + brelse(bh); + err = nilfs_ifile_create_inode(root->ifile, &ino, &bh); + if (unlikely(err)) + goto failed_ifile_create_inode; + } while (ino < NILFS_USER_INO); + + nilfs_msg(sb, KERN_INFO, + "repaired inode bitmap for reserved inodes"); + } + ii->i_bh = bh; + atomic64_inc(&root->inodes_count); inode_init_owner(inode, dir, mode); inode->i_ino = ino;