The patch titled
Subject: nilfs2: fix use-after-free bug of nilfs_root in nilfs_evict_inode()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
nilfs2-fix-use-after-free-bug-of-nilfs_root-in-nilfs_evict_inode.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-fix-use-after-free-bug-of-nilfs_root-in-nilfs_evict_inode.patch
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@xxxxxxxxx>
Subject: nilfs2: fix use-after-free bug of nilfs_root in nilfs_evict_inode()
Date: Wed, 10 May 2023 00:29:56 +0900
During unmount process of nilfs2, nothing holds nilfs_root structure after
nilfs2 detaches its writer in nilfs_detach_log_writer(). However, since
nilfs_evict_inode() uses nilfs_root for some cleanup operations, it may
cause use-after-free read if inodes are left in "garbage_list" and
released by nilfs_dispose_list() at the end of nilfs_detach_log_writer().
Fix this issue by modifying nilfs_evict_inode() to only clear inode
without additional metadata changes that use nilfs_root if the file system
is degraded to read-only or the writer is detached.
Link: https://lkml.kernel.org/r/20230509152956.8313-1-konishi.ryusuke@xxxxxxxxx
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Reported-by: syzbot+78d4495558999f55d1da@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lkml.kernel.org/r/00000000000099e5ac05fb1c3b85@xxxxxxxxxx
Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/inode.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
--- a/fs/nilfs2/inode.c~nilfs2-fix-use-after-free-bug-of-nilfs_root-in-nilfs_evict_inode
+++ a/fs/nilfs2/inode.c
@@ -917,6 +917,7 @@ void nilfs_evict_inode(struct inode *ino
struct nilfs_transaction_info ti;
struct super_block *sb = inode->i_sb;
struct nilfs_inode_info *ii = NILFS_I(inode);
+ struct the_nilfs *nilfs;
int ret;
if (inode->i_nlink || !ii->i_root || unlikely(is_bad_inode(inode))) {
@@ -929,6 +930,23 @@ void nilfs_evict_inode(struct inode *ino
truncate_inode_pages_final(&inode->i_data);
+ nilfs = sb->s_fs_info;
+ if (unlikely(sb_rdonly(sb) || !nilfs->ns_writer)) {
+ /*
+ * If this inode is about to be disposed after the file system
+ * has been degraded to read-only due to file system corruption
+ * or after the writer has been detached, do not make any
+ * changes that cause writes, just clear it.
+ * Do this check after read-locking ns_segctor_sem by
+ * nilfs_transaction_begin() in order to avoid a race with
+ * the writer detach operation.
+ */
+ clear_inode(inode);
+ nilfs_clear_inode(inode);
+ nilfs_transaction_abort(sb);
+ return;
+ }
+
/* TODO: some of the following operations may fail. */
nilfs_truncate_bmap(ii, 0);
nilfs_mark_inode_dirty(inode);
_
Patches currently in -mm which might be from konishi.ryusuke@xxxxxxxxx are
nilfs2-fix-use-after-free-bug-of-nilfs_root-in-nilfs_evict_inode.patch
