netdev - Re: [PATCH 1/2] net: moxa: do not call dma_unmap

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Date:   Fri, 19 Aug 2022 10:27:35 +0300
From:   Sergei Antonov <saproj@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        Vladimir Oltean <olteanv@...il.com>
Subject: Re: [PATCH 1/2] net: moxa: do not call dma_unmap_single() with null

On Thu, 18 Aug 2022 at 22:18, Andrew Lunn <andrew@...n.ch> wrote:
>
> On Thu, Aug 18, 2022 at 09:29:47PM +0300, Sergei Antonov wrote:
> > It fixes a warning during error unwinding:
> >
> > WARNING: CPU: 0 PID: 1 at kernel/dma/debug.c:963 check_unmap+0x704/0x980
> > DMA-API: moxart-ethernet 92000000.mac: device driver tries to free DMA memory it has not allocated [device address=0x0000000000000000] [size=1600 bytes]
> > CPU: 0 PID: 1 Comm: swapper Not tainted 5.19.0+ #60
> > Hardware name: Generic DT based system
> >  unwind_backtrace from show_stack+0x10/0x14
> >  show_stack from dump_stack_lvl+0x34/0x44
> >  dump_stack_lvl from __warn+0xbc/0x1f0
> >  __warn from warn_slowpath_fmt+0x94/0xc8
> >  warn_slowpath_fmt from check_unmap+0x704/0x980
> >  check_unmap from debug_dma_unmap_page+0x8c/0x9c
> >  debug_dma_unmap_page from moxart_mac_free_memory+0x3c/0xa8
> >  moxart_mac_free_memory from moxart_mac_probe+0x190/0x218
> >  moxart_mac_probe from platform_probe+0x48/0x88
> >  platform_probe from really_probe+0xc0/0x2e4
> >
> > Fixes: 6c821bd9edc9 ("net: Add MOXA ART SoCs ethernet driver")
> > Signed-off-by: Sergei Antonov <saproj@...il.com>
>
> This looks correct as it is:
>
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
>
> But i do wonder how it go into the situation:

An error during moxart_mac_probe() does "goto init_fail;" which calls
moxart_mac_free_memory(). And by that time, priv->rx_mapping[i] are
all zero yet.