From bf7afb29d545a6875fa44e17ddd23398e3dc30de Mon Sep 17 00:00:00 2001 From: Russell King Date: Thu, 23 Jun 2016 14:50:25 +0100 Subject: [PATCH] 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 Signed-off-by: Russell King Signed-off-by: David S. Miller --- 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 0dfed86bdb5a..b376ada83598 100644 --- a/drivers/net/phy/fixed_phy.c +++ b/drivers/net/phy/fixed_phy.c @@ -23,6 +23,7 @@ #include #include #include +#include #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; -- 2.20.1