linux-kernel - Re: [PATCH] jffs2: fix nothing output for "ls" command

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Message-ID: <CAFLxGvzkMp3JJHiE3g3LrxVJUgh2Fj6tbGFPSdv-1W2PiYqGjQ@mail.gmail.com>
Date:   Wed, 3 Jun 2020 09:18:29 +0200
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     Zhe Li <lizhe67@...wei.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        linux-mtd@...ts.infradead.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] jffs2: fix nothing output for "ls" command

On Fri, May 29, 2020 at 5:38 AM Zhe Li <lizhe67@...wei.com> wrote:
>
> Recently I find a bug that I get nothing with shell
> command "ls". The test steps are listed below.
> 1. cd $JFFS2_MOUNT_DIR
> 2. touch file
> 3. ls
>
> Finally I find that when command "ls" going into
> function jffs2_readdir(), it get non-zero return
> value from function dir_emit(). So I get nothing
> from "ls", absolutely.
>
> After checking my file system image, I find a raw
> dirent node with nsize = 0. The full_scan mounting
> process do not check nsize and the return value
> of strnlen(rd->name, rd->nsize) carefully, which
> causes function jffs2_readdir pass 0 to parameter
> namelen of function dir_emit when we use command
> "ls".
>
> Of course it should never happened to find a raw
> dirent with nsize = 0. In my opinion, this abnormal
> phenomenon maybe cause by bad driver or bad medium.
> But for rebustness reason, jffs2 should handle it.

Well, if driver or medium are bad, the filesystem will die and lose
data. Instead of papering over the issue and delaying the inevitable
loss of data, please address the root cause.

-- 
Thanks,
//richard