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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>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Russell King 2016-06-23 14:50:25 +01:00 committed by David S. Miller
parent 37688e3f53
commit bf7afb29d5
1 changed files with 21 additions and 7 deletions
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28
drivers/net/phy/fixed_phy.c
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@ -23,6 +23,7 @@
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/gpio.h>
#include <linux/seqlock.h>
#include "swphy.h"
@ -34,6 +35,7 @@ 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;
@ -58,13 +60,21 @@ static int fixed_mdio_read(struct mii_bus *bus, int phy_addr, int reg_num)
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);
}
}
@ -116,6 +126,7 @@ int fixed_phy_update_state(struct phy_device *phydev,
list_for_each_entry(fp, &fmb->phys, node) {
if (fp->addr == phydev->mdio.addr) {
write_seqcount_begin(&fp->seqcount);
#define _UPD(x) if (changed->x) \
fp->status.x = status->x
_UPD(link);
@ -125,6 +136,7 @@ int fixed_phy_update_state(struct phy_device *phydev,
_UPD(asym_pause);
#undef _UPD
fixed_phy_update(fp);
write_seqcount_end(&fp->seqcount);
return 0;
}
}
@ -149,6 +161,8 @@ int fixed_phy_add(unsigned int irq, int phy_addr,
if (!fp)
return -ENOMEM;
seqcount_init(&fp->seqcount);
if (irq != PHY_POLL)
fmb->mii_bus->irq[phy_addr] = irq;