From: Vladimir Oltean vladimir.oltean@nxp.com
[ Upstream commit db46e3a88a09c5cf7e505664d01da7238cd56c92 ]
In an incredibly strange API design decision, qdisc->destroy() gets called even if qdisc->init() never succeeded, not exclusively since commit 87b60cfacf9f ("net_sched: fix error recovery at qdisc creation"), but apparently also earlier (in the case of qdisc_create_dflt()).
The taprio qdisc does not fully acknowledge this when it attempts full offload, because it starts off with q->flags = TAPRIO_FLAGS_INVALID in taprio_init(), then it replaces q->flags with TCA_TAPRIO_ATTR_FLAGS parsed from netlink (in taprio_change(), tail called from taprio_init()).
But in taprio_destroy(), we call taprio_disable_offload(), and this determines what to do based on FULL_OFFLOAD_IS_ENABLED(q->flags).
But looking at the implementation of FULL_OFFLOAD_IS_ENABLED() (a bitwise check of bit 1 in q->flags), it is invalid to call this macro on q->flags when it contains TAPRIO_FLAGS_INVALID, because that is set to U32_MAX, and therefore FULL_OFFLOAD_IS_ENABLED() will return true on an invalid set of flags.
As a result, it is possible to crash the kernel if user space forces an error between setting q->flags = TAPRIO_FLAGS_INVALID, and the calling of taprio_enable_offload(). This is because drivers do not expect the offload to be disabled when it was never enabled.
The error that we force here is to attach taprio as a non-root qdisc, but instead as child of an mqprio root qdisc:
$ tc qdisc add dev swp0 root handle 1: \ mqprio num_tc 8 map 0 1 2 3 4 5 6 7 \ queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 hw 0 $ tc qdisc replace dev swp0 parent 1:1 \ taprio num_tc 8 map 0 1 2 3 4 5 6 7 \ queues 1@0 1@1 1@2 1@3 1@4 1@5 1@6 1@7 base-time 0 \ sched-entry S 0x7f 990000 sched-entry S 0x80 100000 \ flags 0x0 clockid CLOCK_TAI Unable to handle kernel paging request at virtual address fffffffffffffff8 [fffffffffffffff8] pgd=0000000000000000, p4d=0000000000000000 Internal error: Oops: 96000004 [#1] PREEMPT SMP Call trace: taprio_dump+0x27c/0x310 vsc9959_port_setup_tc+0x1f4/0x460 felix_port_setup_tc+0x24/0x3c dsa_slave_setup_tc+0x54/0x27c taprio_disable_offload.isra.0+0x58/0xe0 taprio_destroy+0x80/0x104 qdisc_create+0x240/0x470 tc_modify_qdisc+0x1fc/0x6b0 rtnetlink_rcv_msg+0x12c/0x390 netlink_rcv_skb+0x5c/0x130 rtnetlink_rcv+0x1c/0x2c
Fix this by keeping track of the operations we made, and undo the offload only if we actually did it.
I've added "bool offloaded" inside a 4 byte hole between "int clockid" and "atomic64_t picos_per_byte". Now the first cache line looks like below:
$ pahole -C taprio_sched net/sched/sch_taprio.o struct taprio_sched { struct Qdisc * * qdiscs; /* 0 8 */ struct Qdisc * root; /* 8 8 */ u32 flags; /* 16 4 */ enum tk_offsets tk_offset; /* 20 4 */ int clockid; /* 24 4 */ bool offloaded; /* 28 1 */
/* XXX 3 bytes hole, try to pack */
atomic64_t picos_per_byte; /* 32 0 */
/* XXX 8 bytes hole, try to pack */
spinlock_t current_entry_lock; /* 40 0 */
/* XXX 8 bytes hole, try to pack */
struct sched_entry * current_entry; /* 48 8 */ struct sched_gate_list * oper_sched; /* 56 8 */ /* --- cacheline 1 boundary (64 bytes) --- */
Fixes: 9c66d1564676 ("taprio: Add support for hardware offloading") Signed-off-by: Vladimir Oltean vladimir.oltean@nxp.com Reviewed-by: Vinicius Costa Gomes vinicius.gomes@intel.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/sch_taprio.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index eca525791013..384316c11e98 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -65,6 +65,7 @@ struct taprio_sched { u32 flags; enum tk_offsets tk_offset; int clockid; + bool offloaded; atomic64_t picos_per_byte; /* Using picoseconds because for 10Gbps+ * speeds it's sub-nanoseconds per byte */ @@ -1267,6 +1268,8 @@ static int taprio_enable_offload(struct net_device *dev, goto done; }
+ q->offloaded = true; + done: taprio_offload_free(offload);
@@ -1281,12 +1284,9 @@ static int taprio_disable_offload(struct net_device *dev, struct tc_taprio_qopt_offload *offload; int err;
- if (!FULL_OFFLOAD_IS_ENABLED(q->flags)) + if (!q->offloaded) return 0;
- if (!ops->ndo_setup_tc) - return -EOPNOTSUPP; - offload = taprio_offload_alloc(0); if (!offload) { NL_SET_ERR_MSG(extack, @@ -1302,6 +1302,8 @@ static int taprio_disable_offload(struct net_device *dev, goto out; }
+ q->offloaded = false; + out: taprio_offload_free(offload);