linux-kernel - [PATCH v2 0/3] net: phy: leds: Fix truncated LED trigger names and crashes

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Date:   Wed, 25 Jan 2017 11:39:47 +0100
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>,
        Zach Brown <zach.brown@...com>,
        Volodymyr Bendiuga <volodymyr.bendiuga@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Magnus Öberg <magnus.oberg@...termo.se>,
        netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH v2 0/3] net: phy: leds: Fix truncated LED trigger names and crashes

	Hi David,

I started seeing crashes during s2ram and poweroff on all my ARM boards,
like:

    Unable to handle kernel NULL pointer dereference at virtual address 00000000
    ...
    [<c04116d4>] (__list_del_entry_valid) from [<c05e8948>] (led_trigger_unregister+0x34/0xcc)
    [<c05e8948>] (led_trigger_unregister) from [<c05336c4>] (phy_led_triggers_unregister+0x28/0x34)
    [<c05336c4>] (phy_led_triggers_unregister) from [<c0531d44>] (phy_detach+0x30/0x74)
    [<c0531d44>] (phy_detach) from [<c0538bdc>] (sh_eth_close+0x64/0x9c)
    [<c0538bdc>] (sh_eth_close) from [<c04d4ce0>] (dpm_run_callback+0x48/0xc8)

or:

    list_del corruption. prev->next should be dede6540, but was 2e323931
    ------------[ cut here ]------------
    kernel BUG at lib/list_debug.c:52!
    ...
    [<c02f6d70>] (__list_del_entry_valid) from [<c0425168>] (led_trigger_unregister+0x34/0xcc)
    [<c0425168>] (led_trigger_unregister) from [<c03a05a0>] (phy_led_triggers_unregister+0x28/0x34)
    [<c03a05a0>] (phy_led_triggers_unregister) from [<c039ec04>] (phy_detach+0x30/0x74)
    [<c039ec04>] (phy_detach) from [<c03a4fc0>] (sh_eth_close+0x6c/0xa4)
    [<c03a4fc0>] (sh_eth_close) from [<c0483234>] (__dev_close_many+0xac/0xd0)

As the only clue was a kernel message like

    sh-eth ee700000.ethernet eth0: No phy led trigger registered for speed(100)

I had to bisected this, leading to commit 4567d686f5c6d955 ("phy:
increase size of MII_BUS_ID_SIZE and bus_id").  Reverting that commit
fixed the issue.

More investigation revealed the crashes are due to the combination of
two things:
  - Truncated LED trigger names, leading to duplicate names, and
    registration failures,
  - Bad error handling in case of registration failures.

Both are fixed by this patch series.

Changes compared to v1:
  - Add Reviewed-by,
  - New patch "net: phy: leds: Break dependency of phy.h on
    phy_led_triggers.h",
  - Drop moving the include of <linux/phy_led_triggers.h>, as
    <linux/phy.h> no longer includes it,
  - #include <linux/phy.h> from <linux/phy_led_triggers.h>.

Thanks!

Geert Uytterhoeven (3):
  net: phy: leds: Clear phy_num_led_triggers on failure to avoid crash
  net: phy: leds: Break dependency of phy.h on phy_led_triggers.h
  net: phy: leds: Fix truncated LED trigger names

 drivers/net/phy/phy.c              | 1 +
 drivers/net/phy/phy_led_triggers.c | 9 +++++++--
 include/linux/phy.h                | 1 -
 include/linux/phy_led_triggers.h   | 4 ++--
 4 files changed, 10 insertions(+), 5 deletions(-)

-- 
1.9.1

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds