Re: [PATCH] jffs2: ensure wbuf_verify is valid before using it.

[Hou Tao]

ping ?

On 2018/10/20 20:08, Hou Tao wrote:
> Now MTD emulated by UBI volumn doesn't allocate wbuf_verify in
> jffs2_ubivol_setup(), because UBI can do the verifcation itself,
> so when CONFIG_JFFS2_FS_WBUF_VERIFY is enabled and a MTD device
> emulated by UBI volumn is used, a Oops will occur as show in the
> following trace:
> 
>     general protection fault: 0000 [#1] SMP KASAN PTI
>     CPU: 6 PID: 404 Comm: kworker/6:1 Not tainted 4.19.0-rc8
>     Workqueue: events_long delayed_wbuf_sync
>     RIP: 0010:ubi_io_read+0x156/0x650
>     Call Trace:
>      ubi_eba_read_leb+0x57d/0xba0
>      ubi_leb_read+0xe5/0x1b0
>      gluebi_read+0x10c/0x1a0
>      mtd_read+0x112/0x340
>      jffs2_verify_write+0xef/0x440
>      __jffs2_flush_wbuf+0x3fa/0x3540
>      jffs2_flush_wbuf_gc+0x1b1/0x2e0
>      process_one_work+0x58b/0x11e0
>      worker_thread+0x8f/0xfe0
>      kthread+0x2ae/0x3a0
>      ret_from_fork+0x35/0x40
> 
> Fix the problem by checking the validity of wbuf_verify before
> using it in jffs2_verify_write().
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 0029da3bf430 ("JFFS2: add UBI support")
> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
> ---
>  fs/jffs2/wbuf.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/fs/jffs2/wbuf.c b/fs/jffs2/wbuf.c
> index c6821a509481..3de45f4559d1 100644
> --- a/fs/jffs2/wbuf.c
> +++ b/fs/jffs2/wbuf.c
> @@ -234,6 +234,13 @@ static int jffs2_verify_write(struct jffs2_sb_info *c, unsigned char *buf,
>  	size_t retlen;
>  	char *eccstr;
>  
> +	/*
> +	 * MTD emulated by UBI volume doesn't allocate wbuf_verify,
> +	 * because it can do the verification itself.
> +	 */
> +	if (!c->wbuf_verify)
> +		return 0;
> +
>  	ret = mtd_read(c->mtd, ofs, c->wbuf_pagesize, &retlen, c->wbuf_verify);
>  	if (ret && ret != -EUCLEAN && ret != -EBADMSG) {
>  		pr_warn("%s(): Read back of page at %08x failed: %d\n",
>