| Message ID | 20210820090313.299483-1-mailhol.vincent@wanadoo.fr (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | can: netlink: prevent incoherent can configuration in case of early return | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Series ignored based on subject |
Replying to myself... On Fri. 20 Aug 2021 at 18:03, Vincent Mailhol <mailhol.vincent@wanadoo.fr> wrote: > struct can_priv has a set of flags (can_priv::ctrlmode) which are > correlated with the other field 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. > > Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr> > --- > Hi Marc, > > Do you think this need a "Fixes" tag? > If yes, feel free to add this line to the patch: > > Fixes: 9859ccd2c8be ("can: introduce the data bitrate configuration for CAN FD") > --- > drivers/net/can/dev/netlink.c | 86 ++++++++++++++++++----------------- > 1 file changed, 45 insertions(+), 41 deletions(-) > > diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c > index 80425636049d..6a14c51a058b 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 static declaration is OK > + */ > + 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() retrieves can_priv from the network device and directly writes its changes to it. I will send a v2 in which I will change the prototype of can_calc_tdco() so that the changes are written to the temporary priv instead. > - 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; > } Yours sincerely, Vincent Mailhol
diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c index 80425636049d..6a14c51a058b 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 static declaration is OK + */ + 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); - 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; }
struct can_priv has a set of flags (can_priv::ctrlmode) which are correlated with the other field 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. Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr> --- Hi Marc, Do you think this need a "Fixes" tag? If yes, feel free to add this line to the patch: Fixes: 9859ccd2c8be ("can: introduce the data bitrate configuration for CAN FD") --- drivers/net/can/dev/netlink.c | 86 ++++++++++++++++++----------------- 1 file changed, 45 insertions(+), 41 deletions(-)