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nilfs2: fix use-after-free bug of struct nilfs_root

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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 <konishi.ryusuke@gmail.com>
Reported-by: syzbot+b8c672b0e22615c80fe0@syzkaller.appspotmail.com
Reported-by: Khalid Masum <khalid.masum.92@gmail.com>
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ryusuke Konishi 2022-10-04 00:05:19 +09:00 committed by Andrew Morton
parent b1f44cdaba
commit d325dc6eb7
1 changed files with 16 additions and 1 deletions
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17
fs/nilfs2/inode.c
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@ -328,6 +328,7 @@ 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;
@ -343,11 +344,25 @@ 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_warn(sb,
"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_info(sb, "repaired inode bitmap for reserved inodes");
}
ii->i_bh = bh;
atomic64_inc(&root->inodes_count);
inode_init_owner(&init_user_ns, inode, dir, mode);
inode->i_ino = ino;