From: Davide Caratti dcaratti@redhat.com
[ Upstream commit cd9b50adc6bb9ad3f7d244590a389522215865c4 ]
While running kselftests, Hangbin observed that sch_ets.sh often crashes, and splats like the following one are seen in the output of 'dmesg':
BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 159f12067 P4D 159f12067 PUD 159f13067 PMD 0 Oops: 0000 [#1] SMP NOPTI CPU: 2 PID: 921 Comm: tc Not tainted 5.14.0-rc6+ #458 Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014 RIP: 0010:__list_del_entry_valid+0x2d/0x50 Code: 48 8b 57 08 48 b9 00 01 00 00 00 00 ad de 48 39 c8 0f 84 ac 6e 5b 00 48 b9 22 01 00 00 00 00 ad de 48 39 ca 0f 84 cf 6e 5b 00 <48> 8b 32 48 39 fe 0f 85 af 6e 5b 00 48 8b 50 08 48 39 f2 0f 85 94 RSP: 0018:ffffb2da005c3890 EFLAGS: 00010217 RAX: 0000000000000000 RBX: ffff9073ba23f800 RCX: dead000000000122 RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff9073ba23fbc8 RBP: ffff9073ba23f890 R08: 0000000000000001 R09: 0000000000000001 R10: 0000000000000001 R11: 0000000000000001 R12: dead000000000100 R13: ffff9073ba23fb00 R14: 0000000000000002 R15: 0000000000000002 FS: 00007f93e5564e40(0000) GS:ffff9073bba00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 000000014ad34000 CR4: 0000000000350ee0 Call Trace: ets_qdisc_reset+0x6e/0x100 [sch_ets] qdisc_reset+0x49/0x1d0 tbf_reset+0x15/0x60 [sch_tbf] qdisc_reset+0x49/0x1d0 dev_reset_queue.constprop.42+0x2f/0x90 dev_deactivate_many+0x1d3/0x3d0 dev_deactivate+0x56/0x90 qdisc_graft+0x47e/0x5a0 tc_get_qdisc+0x1db/0x3e0 rtnetlink_rcv_msg+0x164/0x4c0 netlink_rcv_skb+0x50/0x100 netlink_unicast+0x1a5/0x280 netlink_sendmsg+0x242/0x480 sock_sendmsg+0x5b/0x60 ____sys_sendmsg+0x1f2/0x260 ___sys_sendmsg+0x7c/0xc0 __sys_sendmsg+0x57/0xa0 do_syscall_64+0x3a/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f93e44b8338 Code: 89 02 48 c7 c0 ff ff ff ff eb b5 0f 1f 80 00 00 00 00 f3 0f 1e fa 48 8d 05 25 43 2c 00 8b 00 85 c0 75 17 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 58 c3 0f 1f 80 00 00 00 00 41 54 41 89 d4 55 RSP: 002b:00007ffc0db737a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000061255c06 RCX: 00007f93e44b8338 RDX: 0000000000000000 RSI: 00007ffc0db73810 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 000000000000000b R11: 0000000000000246 R12: 0000000000000001 R13: 0000000000687880 R14: 0000000000000000 R15: 0000000000000000 Modules linked in: sch_ets sch_tbf dummy rfkill iTCO_wdt iTCO_vendor_support intel_rapl_msr intel_rapl_common joydev i2c_i801 pcspkr i2c_smbus lpc_ich virtio_balloon ip_tables xfs libcrc32c crct10dif_pclmul crc32_pclmul crc32c_intel ahci libahci ghash_clmulni_intel libata serio_raw virtio_blk virtio_console virtio_net net_failover failover sunrpc dm_mirror dm_region_hash dm_log dm_mod CR2: 0000000000000000
When the change() function decreases the value of 'nstrict', we must take into account that packets might be already enqueued on a class that flips from 'strict' to 'quantum': otherwise that class will not be added to the bandwidth-sharing list. Then, a call to ets_qdisc_reset() will attempt to do list_del(&alist) with 'alist' filled with zero, hence the NULL pointer dereference. For classes flipping from 'strict' to 'quantum', initialize an empty list and eventually add it to the bandwidth-sharing list, if there are packets already enqueued. In this way, the kernel will: a) prevent crashing as described above. b) avoid retaining the backlog packets (for an arbitrarily long time) in case no packet is enqueued after a change from 'strict' to 'quantum'.
Reported-by: Hangbin Liu liuhangbin@gmail.com Fixes: dcc68b4d8084 ("net: sch_ets: Add a new Qdisc") Signed-off-by: Davide Caratti dcaratti@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/sch_ets.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/net/sched/sch_ets.c b/net/sched/sch_ets.c index c1e84d1eeaba..c76701ac35ab 100644 --- a/net/sched/sch_ets.c +++ b/net/sched/sch_ets.c @@ -660,6 +660,13 @@ static int ets_qdisc_change(struct Qdisc *sch, struct nlattr *opt, sch_tree_lock(sch);
q->nbands = nbands; + for (i = nstrict; i < q->nstrict; i++) { + INIT_LIST_HEAD(&q->classes[i].alist); + if (q->classes[i].qdisc->q.qlen) { + list_add_tail(&q->classes[i].alist, &q->active); + q->classes[i].deficit = quanta[i]; + } + } q->nstrict = nstrict; memcpy(q->prio2band, priomap, sizeof(priomap));