1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
|
From c36739c3cfd277a4cc9820a29dd0f4b7fbac795b Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@arm.linux.org.uk>
Date: Sun, 20 Sep 2015 18:31:36 +0100
Subject: [PATCH 713/744] phy: improve safety of fixed-phy MII register reading
There is no prevention of a concurrent call to both fixed_mdio_read()
and fixed_phy_update_state(), which can result in the state being
modified while it's being inspected. Fix this by using a seqcount
to detect modifications, and memcpy()ing the state.
We remain slightly naughty here, calling link_update() and updating
the link status within the read-side loop - which would need rework
of the design to change.
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
drivers/net/phy/fixed_phy.c | 28 +++++++++++++++++++++-------
1 file changed, 21 insertions(+), 7 deletions(-)
--- a/drivers/net/phy/fixed_phy.c
+++ b/drivers/net/phy/fixed_phy.c
@@ -23,6 +23,7 @@
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/gpio.h>
+#include <linux/seqlock.h>
#include "swphy.h"
@@ -35,6 +36,7 @@ struct fixed_mdio_bus {
struct fixed_phy {
int addr;
struct phy_device *phydev;
+ seqcount_t seqcount;
struct fixed_phy_status status;
int (*link_update)(struct net_device *, struct fixed_phy_status *);
struct list_head node;
@@ -59,13 +61,21 @@ static int fixed_mdio_read(struct mii_bu
list_for_each_entry(fp, &fmb->phys, node) {
if (fp->addr == phy_addr) {
- /* Issue callback if user registered it. */
- if (fp->link_update) {
- fp->link_update(fp->phydev->attached_dev,
- &fp->status);
- fixed_phy_update(fp);
- }
- return swphy_read_reg(reg_num, &fp->status);
+ struct fixed_phy_status state;
+ int s;
+
+ do {
+ s = read_seqcount_begin(&fp->seqcount);
+ /* Issue callback if user registered it. */
+ if (fp->link_update) {
+ fp->link_update(fp->phydev->attached_dev,
+ &fp->status);
+ fixed_phy_update(fp);
+ }
+ state = fp->status;
+ } while (read_seqcount_retry(&fp->seqcount, s));
+
+ return swphy_read_reg(reg_num, &state);
}
}
@@ -117,6 +127,7 @@ int fixed_phy_update_state(struct phy_de
list_for_each_entry(fp, &fmb->phys, node) {
if (fp->addr == phydev->addr) {
+ write_seqcount_begin(&fp->seqcount);
#define _UPD(x) if (changed->x) \
fp->status.x = status->x
_UPD(link);
@@ -126,6 +137,7 @@ int fixed_phy_update_state(struct phy_de
_UPD(asym_pause);
#undef _UPD
fixed_phy_update(fp);
+ write_seqcount_end(&fp->seqcount);
return 0;
}
}
@@ -150,6 +162,8 @@ int fixed_phy_add(unsigned int irq, int
if (!fp)
return -ENOMEM;
+ seqcount_init(&fp->seqcount);
+
fmb->irqs[phy_addr] = irq;
fp->addr = phy_addr;
|
