[PATCH RFC 05/26] phy: improve safety of fixed-phy MII register reading
From: Russell King <hidden>
Date: 2015-12-07 17:37:39
Subsystem:
ethernet phy library, networking drivers, the rest · Maintainers:
Andrew Lunn, Heiner Kallweit, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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. Signed-off-by: Russell King <redacted> --- drivers/net/phy/fixed_phy.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/drivers/net/phy/fixed_phy.c b/drivers/net/phy/fixed_phy.c
index 66555da2ef27..474cc39a5457 100644
--- 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_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); } }
@@ -117,6 +127,7 @@ int fixed_phy_update_state(struct phy_device *phydev, 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_device *phydev, _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 phy_addr, if (!fp) return -ENOMEM; + seqcount_init(&fp->seqcount); + fmb->irqs[phy_addr] = irq; fp->addr = phy_addr;
--
2.1.0