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[PATCH 1/2] net: phy: leds: Clear phy_num_led_triggers on failure to avoid crash

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  [PATCH 1/2] net: phy: leds: Clear phy_num_led_triggers on failure to avoid crash Geert Uytterhoeven <geert+renesas@glider.be> - 2017-01-24 16:50 +0100
    Re: [PATCH 1/2] net: phy: leds: Clear phy_num_led_triggers on failure  to avoid crash Florian Fainelli <f.fainelli@gmail.com> - 2017-01-24 22:00 +0100

#1565946 — [PATCH 1/2] net: phy: leds: Clear phy_num_led_triggers on failure to avoid crash

phy_attach_direct() ignores errors returned by
phy_led_triggers_register(). I think that's OK, as LED triggers can be
considered a non-critical feature.

However, this causes problems later:
  - phy_led_trigger_change_speed() will access the array
    phy_device.phy_led_triggers, which has been freed in the error path
    of phy_led_triggers_register(), which may lead to a crash.

  - phy_led_triggers_unregister() will access the same array, leading to
    crashes during s2ram or poweroff, 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)

To fix this, clear phy_device.phy_num_led_triggers in the error path of
phy_led_triggers_register() fails.

Note that the "No phy led trigger registered for speed" message will
still be printed on link speed changes, which is a good cue that
something went wrong with the LED triggers.

Fixes: 2e0bc452f4721520 ("net: phy: leds: add support for led triggers on phy link state change")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
Alternatively, phy_attach_direct() could consider
phy_led_triggers_register() failures as fatal, so
phy_led_trigger_change_speed() and phy_led_triggers_unregister() are
never called afterwards.

Exposed by commit 4567d686f5c6d955 ("phy: increase size of
MII_BUS_ID_SIZE and bus_id"), which caused duplicate trigger names.
---
 drivers/net/phy/phy_led_triggers.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/phy/phy_led_triggers.c b/drivers/net/phy/phy_led_triggers.c
index fa62bdf2f52694de..3f619e7371e97d8a 100644
--- a/drivers/net/phy/phy_led_triggers.c
+++ b/drivers/net/phy/phy_led_triggers.c
@@ -102,8 +102,10 @@ int phy_led_triggers_register(struct phy_device *phy)
 					    sizeof(struct phy_led_trigger) *
 						   phy->phy_num_led_triggers,
 					    GFP_KERNEL);
-	if (!phy->phy_led_triggers)
-		return -ENOMEM;
+	if (!phy->phy_led_triggers) {
+		err = -ENOMEM;
+		goto out_clear;
+	}
 
 	for (i = 0; i < phy->phy_num_led_triggers; i++) {
 		err = phy_led_trigger_register(phy, &phy->phy_led_triggers[i],
@@ -120,6 +122,8 @@ int phy_led_triggers_register(struct phy_device *phy)
 	while (i--)
 		phy_led_trigger_unregister(&phy->phy_led_triggers[i]);
 	devm_kfree(&phy->mdio.dev, phy->phy_led_triggers);
+out_clear:
+	phy->phy_num_led_triggers = 0;
 	return err;
 }
 EXPORT_SYMBOL_GPL(phy_led_triggers_register);
-- 
1.9.1

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#1566137 — Re: [PATCH 1/2] net: phy: leds: Clear phy_num_led_triggers on failure to avoid crash

On 01/24/2017 07:41 AM, Geert Uytterhoeven wrote:
> phy_attach_direct() ignores errors returned by
> phy_led_triggers_register(). I think that's OK, as LED triggers can be
> considered a non-critical feature.
> 
> However, this causes problems later:
>   - phy_led_trigger_change_speed() will access the array
>     phy_device.phy_led_triggers, which has been freed in the error path
>     of phy_led_triggers_register(), which may lead to a crash.
> 
>   - phy_led_triggers_unregister() will access the same array, leading to
>     crashes during s2ram or poweroff, 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)
> 
> To fix this, clear phy_device.phy_num_led_triggers in the error path of
> phy_led_triggers_register() fails.
> 
> Note that the "No phy led trigger registered for speed" message will
> still be printed on link speed changes, which is a good cue that
> something went wrong with the LED triggers.
> 
> Fixes: 2e0bc452f4721520 ("net: phy: leds: add support for led triggers on phy link state change")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian

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