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Date:   Fri, 23 Jun 2023 08:53:15 -0500
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Subject: Re: [PATCH] FS: JFS: Check for read-only mounted filesystem in
 txBegin
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To:     mirimmad@outlook.com, shaggy@kernel.org
Cc:     Immad Mir <mirimmad17@gmail.com>,
        jfs-discussion@lists.sourceforge.net, linux-kernel@vger.kernel.org
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From:   Dave Kleikamp <dave.kleikamp@oracle.com>
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On 6/23/23 8:47AM, mirimmad@outlook.com wrote:
> From: Immad Mir <mirimmad17@gmail.com>
> 
>   This patch adds a check for read-only mounted filesystem
>   in txBegin before starting a transaction potentially saving
>   from NULL pointer deref.

Thanks. I like this. Not much else we can do since none of the callers 
anticipate an error. I'll push it to jfs-next.

Shaggy

> 
> Signed-off-by: Immad Mir <mirimmad17@gmail.com>
> ---
>   fs/jfs/jfs_txnmgr.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/jfs/jfs_txnmgr.c b/fs/jfs/jfs_txnmgr.c
> index ffd4feece..87dc4e3a4 100644
> --- a/fs/jfs/jfs_txnmgr.c
> +++ b/fs/jfs/jfs_txnmgr.c
> @@ -353,7 +353,10 @@ tid_t txBegin(struct super_block *sb, int flag)
>   
>   	jfs_info("txBegin: flag = 0x%x", flag);
>   	log = JFS_SBI(sb)->log;
> -
> +	if (!log) {
> +		jfs_error(sb, "read-only filesystem\n");
> +		return 0;
> +	}
>   	TXN_LOCK();
>   
>   	INCREMENT(TxStat.txBegin);