The patch titled Subject: nilfs2: fix use-after-free bug of struct nilfs_root has been added to the -mm mm-hotfixes-unstable branch. Its filename is nilfs2-fix-use-after-free-bug-of-struct-nilfs_root.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Ryusuke Konishi konishi.ryusuke@gmail.com Subject: nilfs2: fix use-after-free bug of struct nilfs_root Date: Tue, 4 Oct 2022 00:05:19 +0900

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 ---

fs/nilfs2/inode.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)

--- a/fs/nilfs2/inode.c~nilfs2-fix-use-after-free-bug-of-struct-nilfs_root +++ a/fs/nilfs2/inode.c @@ -328,6 +328,7 @@ struct inode *nilfs_new_inode(struct ino 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 ino 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; _

Patches currently in -mm which might be from konishi.ryusuke@gmail.com are

nilfs2-fix-use-after-free-bug-of-struct-nilfs_root.patch nilfs2-replace-warn_ons-by-nilfs_error-for-checkpoint-acquisition-failure.patch