[RESEND PATCH v2] can: netlink: prevent incoherent can configuration in case of early return
From: Vincent Mailhol <hidden>
Date: 2021-09-03 07:18:29
struct can_priv has a set of flags (can_priv::ctrlmode) which are
correlated with the other fields of the structure. In
can_changelink(), those flags are set first and copied to can_priv. If
the function has to return early, for example due to an out of range
value provided by the user, then the global configuration might become
incoherent.
Example: the user provides an out of range dbitrate (e.g. 20
Mbps). The command fails (-EINVAL), however the FD flag was already
set resulting in a configuration where FD is on but the databittiming
parameters are empty.
* Illustration of above example *
| $ ip link set can0 type can bitrate 500000 dbitrate 20000000 fd on
| RTNETLINK answers: Invalid argument
| $ ip --details link show can0
| 1: can0: <NOARP,ECHO> mtu 72 qdisc noop state DOWN mode DEFAULT group default qlen 10
| link/can promiscuity 0 minmtu 0 maxmtu 0
| can <FD> state STOPPED restart-ms 0
^^ FD flag is set without any of the databittiming parameters...
| bitrate 500000 sample-point 0.875
| tq 12 prop-seg 69 phase-seg1 70 phase-seg2 20 sjw 1
| ES582.1/ES584.1: tseg1 2..256 tseg2 2..128 sjw 1..128 brp 1..512 brp-inc 1
| ES582.1/ES584.1: dtseg1 2..32 dtseg2 1..16 dsjw 1..8 dbrp 1..32 dbrp-inc 1
| clock 80000000 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
To prevent this from happening, we do a local copy of can_priv, work
on it, an copy it at the very end of the function (i.e. only if all
previous checks succeeded).
Once this done, there is no more need to have a temporary variable for
a specific parameter. As such, the bittiming and data bittiming (bt
and dbt) are directly written to the temporary priv variable.
Finally, function can_calc_tdco() was retrieving can_priv from the
net_device and directly modifying it. We changed the prototype so that
it instead writes its changes into our temporary priv variable.
Signed-off-by: Vincent Mailhol <redacted>
---
Resending because I got no answers on:
https://lore.kernel.org/linux-can/20210823024750.702542-1-mailhol.vincent@wanadoo.fr/T/#u
(I guess everyone bas busy with the upcoming merge window)
I am not sure whether or not this needs a "Fixes" tag. Just in case,
there it is:
Fixes: 9859ccd2c8be ("can: introduce the data bitrate configuration for CAN FD")
* Changelog *
v1 -> v2:
- Change the prototype of can_calc_tdco() so that the changes are
applied to the temporary priv instead of netdev_priv(dev).
---
drivers/net/can/dev/bittiming.c | 8 +--
drivers/net/can/dev/netlink.c | 88 +++++++++++++++++----------------
include/linux/can/bittiming.h | 7 ++-
3 files changed, 53 insertions(+), 50 deletions(-)
diff --git a/drivers/net/can/dev/bittiming.c b/drivers/net/can/dev/bittiming.c
index f49170eadd54..bddd93e2e439 100644
--- a/drivers/net/can/dev/bittiming.c
+++ b/drivers/net/can/dev/bittiming.c@@ -175,13 +175,9 @@ int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt, return 0; } -void can_calc_tdco(struct net_device *dev) +void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const, + const struct can_bittiming *dbt) { - struct can_priv *priv = netdev_priv(dev); - const struct can_bittiming *dbt = &priv->data_bittiming; - struct can_tdc *tdc = &priv->tdc; - const struct can_tdc_const *tdc_const = priv->tdc_const; - if (!tdc_const) return;
diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c
index 80425636049d..50dfed462711 100644
--- a/drivers/net/can/dev/netlink.c
+++ b/drivers/net/can/dev/netlink.c@@ -58,14 +58,20 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], struct nlattr *data[], struct netlink_ext_ack *extack) { - struct can_priv *priv = netdev_priv(dev); + /* Work on a local copy of priv to prevent inconsistent value + * in case of early return. net/core/rtnetlink.c has a global + * mutex so using a static declaration is race free + */ + static struct can_priv priv; int err; /* We need synchronization with dev->stop() */ ASSERT_RTNL(); + memcpy(&priv, netdev_priv(dev), sizeof(priv)); + if (data[IFLA_CAN_BITTIMING]) { - struct can_bittiming bt; + struct can_bittiming *bt = &priv.bittiming; /* Do not allow changing bittiming while running */ if (dev->flags & IFF_UP)
@@ -76,28 +82,26 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], * directly via do_set_bitrate(). Bail out if neither * is given. */ - if (!priv->bittiming_const && !priv->do_set_bittiming) + if (!priv.bittiming_const && !priv.do_set_bittiming) return -EOPNOTSUPP; - memcpy(&bt, nla_data(data[IFLA_CAN_BITTIMING]), sizeof(bt)); - err = can_get_bittiming(dev, &bt, - priv->bittiming_const, - priv->bitrate_const, - priv->bitrate_const_cnt); + memcpy(bt, nla_data(data[IFLA_CAN_BITTIMING]), sizeof(*bt)); + err = can_get_bittiming(dev, bt, + priv.bittiming_const, + priv.bitrate_const, + priv.bitrate_const_cnt); if (err) return err; - if (priv->bitrate_max && bt.bitrate > priv->bitrate_max) { + if (priv.bitrate_max && bt->bitrate > priv.bitrate_max) { netdev_err(dev, "arbitration bitrate surpasses transceiver capabilities of %d bps\n", - priv->bitrate_max); + priv.bitrate_max); return -EINVAL; } - memcpy(&priv->bittiming, &bt, sizeof(bt)); - - if (priv->do_set_bittiming) { + if (priv.do_set_bittiming) { /* Finally, set the bit-timing registers */ - err = priv->do_set_bittiming(dev); + err = priv.do_set_bittiming(dev); if (err) return err; }
@@ -112,11 +116,11 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], if (dev->flags & IFF_UP) return -EBUSY; cm = nla_data(data[IFLA_CAN_CTRLMODE]); - ctrlstatic = priv->ctrlmode_static; + ctrlstatic = priv.ctrlmode_static; maskedflags = cm->flags & cm->mask; /* check whether provided bits are allowed to be passed */ - if (maskedflags & ~(priv->ctrlmode_supported | ctrlstatic)) + if (maskedflags & ~(priv.ctrlmode_supported | ctrlstatic)) return -EOPNOTSUPP; /* do not check for static fd-non-iso if 'fd' is disabled */
@@ -128,16 +132,16 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], return -EOPNOTSUPP; /* clear bits to be modified and copy the flag values */ - priv->ctrlmode &= ~cm->mask; - priv->ctrlmode |= maskedflags; + priv.ctrlmode &= ~cm->mask; + priv.ctrlmode |= maskedflags; /* CAN_CTRLMODE_FD can only be set when driver supports FD */ - if (priv->ctrlmode & CAN_CTRLMODE_FD) { + if (priv.ctrlmode & CAN_CTRLMODE_FD) { dev->mtu = CANFD_MTU; } else { dev->mtu = CAN_MTU; - memset(&priv->data_bittiming, 0, - sizeof(priv->data_bittiming)); + memset(&priv.data_bittiming, 0, + sizeof(priv.data_bittiming)); } }
@@ -145,7 +149,7 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], /* Do not allow changing restart delay while running */ if (dev->flags & IFF_UP) return -EBUSY; - priv->restart_ms = nla_get_u32(data[IFLA_CAN_RESTART_MS]); + priv.restart_ms = nla_get_u32(data[IFLA_CAN_RESTART_MS]); } if (data[IFLA_CAN_RESTART]) {
@@ -158,7 +162,7 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], } if (data[IFLA_CAN_DATA_BITTIMING]) { - struct can_bittiming dbt; + struct can_bittiming *dbt = &priv.data_bittiming; /* Do not allow changing bittiming while running */ if (dev->flags & IFF_UP)
@@ -169,31 +173,29 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], * directly via do_set_bitrate(). Bail out if neither * is given. */ - if (!priv->data_bittiming_const && !priv->do_set_data_bittiming) + if (!priv.data_bittiming_const && !priv.do_set_data_bittiming) return -EOPNOTSUPP; - memcpy(&dbt, nla_data(data[IFLA_CAN_DATA_BITTIMING]), - sizeof(dbt)); - err = can_get_bittiming(dev, &dbt, - priv->data_bittiming_const, - priv->data_bitrate_const, - priv->data_bitrate_const_cnt); + memcpy(dbt, nla_data(data[IFLA_CAN_DATA_BITTIMING]), + sizeof(*dbt)); + err = can_get_bittiming(dev, dbt, + priv.data_bittiming_const, + priv.data_bitrate_const, + priv.data_bitrate_const_cnt); if (err) return err; - if (priv->bitrate_max && dbt.bitrate > priv->bitrate_max) { + if (priv.bitrate_max && dbt->bitrate > priv.bitrate_max) { netdev_err(dev, "canfd data bitrate surpasses transceiver capabilities of %d bps\n", - priv->bitrate_max); + priv.bitrate_max); return -EINVAL; } - memcpy(&priv->data_bittiming, &dbt, sizeof(dbt)); - - can_calc_tdco(dev); + can_calc_tdco(&priv.tdc, priv.tdc_const, &priv.data_bittiming); - if (priv->do_set_data_bittiming) { + if (priv.do_set_data_bittiming) { /* Finally, set the bit-timing registers */ - err = priv->do_set_data_bittiming(dev); + err = priv.do_set_data_bittiming(dev); if (err) return err; }
@@ -201,28 +203,30 @@ static int can_changelink(struct net_device *dev, struct nlattr *tb[], if (data[IFLA_CAN_TERMINATION]) { const u16 termval = nla_get_u16(data[IFLA_CAN_TERMINATION]); - const unsigned int num_term = priv->termination_const_cnt; + const unsigned int num_term = priv.termination_const_cnt; unsigned int i; - if (!priv->do_set_termination) + if (!priv.do_set_termination) return -EOPNOTSUPP; /* check whether given value is supported by the interface */ for (i = 0; i < num_term; i++) { - if (termval == priv->termination_const[i]) + if (termval == priv.termination_const[i]) break; } if (i >= num_term) return -EINVAL; /* Finally, set the termination value */ - err = priv->do_set_termination(dev, termval); + err = priv.do_set_termination(dev, termval); if (err) return err; - priv->termination = termval; + priv.termination = termval; } + memcpy(netdev_priv(dev), &priv, sizeof(priv)); + return 0; }
diff --git a/include/linux/can/bittiming.h b/include/linux/can/bittiming.h
index 9de6e9053e34..b3c1711ee0f0 100644
--- a/include/linux/can/bittiming.h
+++ b/include/linux/can/bittiming.h@@ -87,7 +87,8 @@ struct can_tdc_const { int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt, const struct can_bittiming_const *btc); -void can_calc_tdco(struct net_device *dev); +void can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const, + const struct can_bittiming *dbt); #else /* !CONFIG_CAN_CALC_BITTIMING */ static inline int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt,
@@ -97,7 +98,9 @@ can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt, return -EINVAL; } -static inline void can_calc_tdco(struct net_device *dev) +static inline void +can_calc_tdco(struct can_tdc *tdc, const struct can_tdc_const *tdc_const, + const struct can_bittiming *dbt) { } #endif /* CONFIG_CAN_CALC_BITTIMING */
--
2.31.1