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Message-ID: <33eea214-56ee-47da-89a7-b4375a5e860c@oracle.com>
Date: Wed, 30 Oct 2024 09:30:28 -0500
From: Dave Kleikamp <dave.kleikamp@...cle.com>
To: Qianqiang Liu <qianqiang.liu@....com>
Cc: jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
syzbot+885a4f3281b8d99c48d8@...kaller.appspotmail.com,
syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] jfs: Fix use-after-free read issue in jfs_lazycommit
On 10/13/24 1:05AM, Qianqiang Liu wrote:
> The jfsCommit kernel thread uses the sbi->commit_state flag,
> and sbi may be freed in jfs_put_super() by another thread.
>
> To prevent this, move commit_state to struct tblock,
> eliminating the need to access the sbi variable.
I need to give this one some more thought. The unmount isn't supposed to
complete before all I/O has completed, but it's been quite I while since
I went over the mechanisms to safeguard that. I'll have to look at this
problem more closely.
Shaggy
>
> Reported-by: syzbot+885a4f3281b8d99c48d8@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=885a4f3281b8d99c48d8
> Tested-by: syzbot+885a4f3281b8d99c48d8@...kaller.appspotmail.com
> Signed-off-by: Qianqiang Liu <qianqiang.liu@....com>
> ---
> fs/jfs/jfs_incore.h | 8 --------
> fs/jfs/jfs_txnmgr.c | 10 ++++------
> fs/jfs/jfs_txnmgr.h | 8 ++++++++
> 3 files changed, 12 insertions(+), 14 deletions(-)
>
> diff --git a/fs/jfs/jfs_incore.h b/fs/jfs/jfs_incore.h
> index 10934f9a11be..7b75c801b239 100644
> --- a/fs/jfs/jfs_incore.h
> +++ b/fs/jfs/jfs_incore.h
> @@ -177,11 +177,6 @@ struct jfs_sb_info {
> pxd_t ait2; /* pxd describing AIT copy */
> uuid_t uuid; /* 128-bit uuid for volume */
> uuid_t loguuid; /* 128-bit uuid for log */
> - /*
> - * commit_state is used for synchronization of the jfs_commit
> - * threads. It is protected by LAZY_LOCK().
> - */
> - int commit_state; /* commit state */
> /* Formerly in ipimap */
> uint gengen; /* inode generation generator*/
> uint inostamp; /* shows inode belongs to fileset*/
> @@ -199,9 +194,6 @@ struct jfs_sb_info {
> uint minblks_trim; /* minimum blocks, for online trim */
> };
>
> -/* jfs_sb_info commit_state */
> -#define IN_LAZYCOMMIT 1
> -
> static inline struct jfs_inode_info *JFS_IP(struct inode *inode)
> {
> return container_of(inode, struct jfs_inode_info, vfs_inode);
> diff --git a/fs/jfs/jfs_txnmgr.c b/fs/jfs/jfs_txnmgr.c
> index be17e3c43582..a4817229d573 100644
> --- a/fs/jfs/jfs_txnmgr.c
> +++ b/fs/jfs/jfs_txnmgr.c
> @@ -2700,7 +2700,6 @@ int jfs_lazycommit(void *arg)
> int WorkDone;
> struct tblock *tblk;
> unsigned long flags;
> - struct jfs_sb_info *sbi;
>
> set_freezable();
> do {
> @@ -2711,17 +2710,16 @@ int jfs_lazycommit(void *arg)
> list_for_each_entry(tblk, &TxAnchor.unlock_queue,
> cqueue) {
>
> - sbi = JFS_SBI(tblk->sb);
> /*
> * For each volume, the transactions must be
> * handled in order. If another commit thread
> * is handling a tblk for this superblock,
> * skip it
> */
> - if (sbi->commit_state & IN_LAZYCOMMIT)
> + if (tblk->commit_state & IN_LAZYCOMMIT)
> continue;
>
> - sbi->commit_state |= IN_LAZYCOMMIT;
> + tblk->commit_state |= IN_LAZYCOMMIT;
> WorkDone = 1;
>
> /*
> @@ -2733,7 +2731,7 @@ int jfs_lazycommit(void *arg)
> txLazyCommit(tblk);
> LAZY_LOCK(flags);
>
> - sbi->commit_state &= ~IN_LAZYCOMMIT;
> + tblk->commit_state &= ~IN_LAZYCOMMIT;
> /*
> * Don't continue in the for loop. (We can't
> * anyway, it's unsafe!) We want to go back to
> @@ -2781,7 +2779,7 @@ void txLazyUnlock(struct tblock * tblk)
> * Don't wake up a commit thread if there is already one servicing
> * this superblock, or if the last one we woke up hasn't started yet.
> */
> - if (!(JFS_SBI(tblk->sb)->commit_state & IN_LAZYCOMMIT) &&
> + if (!(tblk->commit_state & IN_LAZYCOMMIT) &&
> !jfs_commit_thread_waking) {
> jfs_commit_thread_waking = 1;
> wake_up(&jfs_commit_thread_wait);
> diff --git a/fs/jfs/jfs_txnmgr.h b/fs/jfs/jfs_txnmgr.h
> index ba71eb5ced56..3a0ee53f17cb 100644
> --- a/fs/jfs/jfs_txnmgr.h
> +++ b/fs/jfs/jfs_txnmgr.h
> @@ -32,6 +32,11 @@ struct tblock {
>
> /* lock management */
> struct super_block *sb; /* super block */
> + /*
> + * commit_state is used for synchronization of the jfs_commit
> + * threads. It is protected by LAZY_LOCK().
> + */
> + int commit_state; /* commit state */
> lid_t next; /* index of first tlock of tid */
> lid_t last; /* index of last tlock of tid */
> wait_queue_head_t waitor; /* tids waiting on this tid */
> @@ -56,6 +61,9 @@ struct tblock {
> u32 ino; /* inode number being created */
> };
>
> +/* tblock commit_state */
> +#define IN_LAZYCOMMIT 1
> +
> extern struct tblock *TxBlock; /* transaction block table */
>
> /* commit flags: tblk->xflag */
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