-
Notifications
You must be signed in to change notification settings - Fork 11
[LTS 8.8 RT] net: sched: sch_qfq: Fix UAF in qfq_dequeue() #119
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.
Already on GitHub? Sign in to your account
[LTS 8.8 RT] net: sched: sch_qfq: Fix UAF in qfq_dequeue() #119
Conversation
jira VULN-6731 cve CVE-2023-4921 commit-author valis <[email protected]> commit 8fc134f When the plug qdisc is used as a class of the qfq qdisc it could trigger a UAF. This issue can be reproduced with following commands: tc qdisc add dev lo root handle 1: qfq tc class add dev lo parent 1: classid 1:1 qfq weight 1 maxpkt 512 tc qdisc add dev lo parent 1:1 handle 2: plug tc filter add dev lo parent 1: basic classid 1:1 ping -c1 127.0.0.1 and boom: [ 285.353793] BUG: KASAN: slab-use-after-free in qfq_dequeue+0xa7/0x7f0 [ 285.354910] Read of size 4 at addr ffff8880bad312a8 by task ping/144 [ 285.355903] [ 285.356165] CPU: 1 PID: 144 Comm: ping Not tainted 6.5.0-rc3+ ctrliq#4 [ 285.357112] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014 [ 285.358376] Call Trace: [ 285.358773] <IRQ> [ 285.359109] dump_stack_lvl+0x44/0x60 [ 285.359708] print_address_description.constprop.0+0x2c/0x3c0 [ 285.360611] kasan_report+0x10c/0x120 [ 285.361195] ? qfq_dequeue+0xa7/0x7f0 [ 285.361780] qfq_dequeue+0xa7/0x7f0 [ 285.362342] __qdisc_run+0xf1/0x970 [ 285.362903] net_tx_action+0x28e/0x460 [ 285.363502] __do_softirq+0x11b/0x3de [ 285.364097] do_softirq.part.0+0x72/0x90 [ 285.364721] </IRQ> [ 285.365072] <TASK> [ 285.365422] __local_bh_enable_ip+0x77/0x90 [ 285.366079] __dev_queue_xmit+0x95f/0x1550 [ 285.366732] ? __pfx_csum_and_copy_from_iter+0x10/0x10 [ 285.367526] ? __pfx___dev_queue_xmit+0x10/0x10 [ 285.368259] ? __build_skb_around+0x129/0x190 [ 285.368960] ? ip_generic_getfrag+0x12c/0x170 [ 285.369653] ? __pfx_ip_generic_getfrag+0x10/0x10 [ 285.370390] ? csum_partial+0x8/0x20 [ 285.370961] ? raw_getfrag+0xe5/0x140 [ 285.371559] ip_finish_output2+0x539/0xa40 [ 285.372222] ? __pfx_ip_finish_output2+0x10/0x10 [ 285.372954] ip_output+0x113/0x1e0 [ 285.373512] ? __pfx_ip_output+0x10/0x10 [ 285.374130] ? icmp_out_count+0x49/0x60 [ 285.374739] ? __pfx_ip_finish_output+0x10/0x10 [ 285.375457] ip_push_pending_frames+0xf3/0x100 [ 285.376173] raw_sendmsg+0xef5/0x12d0 [ 285.376760] ? do_syscall_64+0x40/0x90 [ 285.377359] ? __static_call_text_end+0x136578/0x136578 [ 285.378173] ? do_syscall_64+0x40/0x90 [ 285.378772] ? kasan_enable_current+0x11/0x20 [ 285.379469] ? __pfx_raw_sendmsg+0x10/0x10 [ 285.380137] ? __sock_create+0x13e/0x270 [ 285.380673] ? __sys_socket+0xf3/0x180 [ 285.381174] ? __x64_sys_socket+0x3d/0x50 [ 285.381725] ? entry_SYSCALL_64_after_hwframe+0x6e/0xd8 [ 285.382425] ? __rcu_read_unlock+0x48/0x70 [ 285.382975] ? ip4_datagram_release_cb+0xd8/0x380 [ 285.383608] ? __pfx_ip4_datagram_release_cb+0x10/0x10 [ 285.384295] ? preempt_count_sub+0x14/0xc0 [ 285.384844] ? __list_del_entry_valid+0x76/0x140 [ 285.385467] ? _raw_spin_lock_bh+0x87/0xe0 [ 285.386014] ? __pfx__raw_spin_lock_bh+0x10/0x10 [ 285.386645] ? release_sock+0xa0/0xd0 [ 285.387148] ? preempt_count_sub+0x14/0xc0 [ 285.387712] ? freeze_secondary_cpus+0x348/0x3c0 [ 285.388341] ? aa_sk_perm+0x177/0x390 [ 285.388856] ? __pfx_aa_sk_perm+0x10/0x10 [ 285.389441] ? check_stack_object+0x22/0x70 [ 285.390032] ? inet_send_prepare+0x2f/0x120 [ 285.390603] ? __pfx_inet_sendmsg+0x10/0x10 [ 285.391172] sock_sendmsg+0xcc/0xe0 [ 285.391667] __sys_sendto+0x190/0x230 [ 285.392168] ? __pfx___sys_sendto+0x10/0x10 [ 285.392727] ? kvm_clock_get_cycles+0x14/0x30 [ 285.393328] ? set_normalized_timespec64+0x57/0x70 [ 285.393980] ? _raw_spin_unlock_irq+0x1b/0x40 [ 285.394578] ? __x64_sys_clock_gettime+0x11c/0x160 [ 285.395225] ? __pfx___x64_sys_clock_gettime+0x10/0x10 [ 285.395908] ? _copy_to_user+0x3e/0x60 [ 285.396432] ? exit_to_user_mode_prepare+0x1a/0x120 [ 285.397086] ? syscall_exit_to_user_mode+0x22/0x50 [ 285.397734] ? do_syscall_64+0x71/0x90 [ 285.398258] __x64_sys_sendto+0x74/0x90 [ 285.398786] do_syscall_64+0x64/0x90 [ 285.399273] ? exit_to_user_mode_prepare+0x1a/0x120 [ 285.399949] ? syscall_exit_to_user_mode+0x22/0x50 [ 285.400605] ? do_syscall_64+0x71/0x90 [ 285.401124] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 [ 285.401807] RIP: 0033:0x495726 [ 285.402233] Code: ff ff ff f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 11 b8 2c 00 00 00 0f 09 [ 285.404683] RSP: 002b:00007ffcc25fb618 EFLAGS: 00000246 ORIG_RAX: 000000000000002c [ 285.405677] RAX: ffffffffffffffda RBX: 0000000000000040 RCX: 0000000000495726 [ 285.406628] RDX: 0000000000000040 RSI: 0000000002518750 RDI: 0000000000000000 [ 285.407565] RBP: 00000000005205ef R08: 00000000005f8838 R09: 000000000000001c [ 285.408523] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000002517634 [ 285.409460] R13: 00007ffcc25fb6f0 R14: 0000000000000003 R15: 0000000000000000 [ 285.410403] </TASK> [ 285.410704] [ 285.410929] Allocated by task 144: [ 285.411402] kasan_save_stack+0x1e/0x40 [ 285.411926] kasan_set_track+0x21/0x30 [ 285.412442] __kasan_slab_alloc+0x55/0x70 [ 285.412973] kmem_cache_alloc_node+0x187/0x3d0 [ 285.413567] __alloc_skb+0x1b4/0x230 [ 285.414060] __ip_append_data+0x17f7/0x1b60 [ 285.414633] ip_append_data+0x97/0xf0 [ 285.415144] raw_sendmsg+0x5a8/0x12d0 [ 285.415640] sock_sendmsg+0xcc/0xe0 [ 285.416117] __sys_sendto+0x190/0x230 [ 285.416626] __x64_sys_sendto+0x74/0x90 [ 285.417145] do_syscall_64+0x64/0x90 [ 285.417624] entry_SYSCALL_64_after_hwframe+0x6e/0xd8 [ 285.418306] [ 285.418531] Freed by task 144: [ 285.418960] kasan_save_stack+0x1e/0x40 [ 285.419469] kasan_set_track+0x21/0x30 [ 285.419988] kasan_save_free_info+0x27/0x40 [ 285.420556] ____kasan_slab_free+0x109/0x1a0 [ 285.421146] kmem_cache_free+0x1c2/0x450 [ 285.421680] __netif_receive_skb_core+0x2ce/0x1870 [ 285.422333] __netif_receive_skb_one_core+0x97/0x140 [ 285.423003] process_backlog+0x100/0x2f0 [ 285.423537] __napi_poll+0x5c/0x2d0 [ 285.424023] net_rx_action+0x2be/0x560 [ 285.424510] __do_softirq+0x11b/0x3de [ 285.425034] [ 285.425254] The buggy address belongs to the object at ffff8880bad31280 [ 285.425254] which belongs to the cache skbuff_head_cache of size 224 [ 285.426993] The buggy address is located 40 bytes inside of [ 285.426993] freed 224-byte region [ffff8880bad31280, ffff8880bad31360) [ 285.428572] [ 285.428798] The buggy address belongs to the physical page: [ 285.429540] page:00000000f4b77674 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xbad31 [ 285.430758] flags: 0x100000000000200(slab|node=0|zone=1) [ 285.431447] page_type: 0xffffffff() [ 285.431934] raw: 0100000000000200 ffff88810094a8c0 dead000000000122 0000000000000000 [ 285.432757] raw: 0000000000000000 00000000800c000c 00000001ffffffff 0000000000000000 [ 285.433562] page dumped because: kasan: bad access detected [ 285.434144] [ 285.434320] Memory state around the buggy address: [ 285.434828] ffff8880bad31180: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 285.435580] ffff8880bad31200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 285.436264] >ffff8880bad31280: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 285.436777] ^ [ 285.437106] ffff8880bad31300: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc [ 285.437616] ffff8880bad31380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 285.438126] ================================================================== [ 285.438662] Disabling lock debugging due to kernel taint Fix this by: 1. Changing sch_plug's .peek handler to qdisc_peek_dequeued(), a function compatible with non-work-conserving qdiscs 2. Checking the return value of qdisc_dequeue_peeked() in sch_qfq. Fixes: 462dbc9 ("pkt_sched: QFQ Plus: fair-queueing service at DRR cost") Reported-by: valis <[email protected]> Signed-off-by: valis <[email protected]> Signed-off-by: Jamal Hadi Salim <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Paolo Abeni <[email protected]> (cherry picked from commit 8fc134f) Signed-off-by: Marcin Wcisło <[email protected]>
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
Starting github runners too
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
In line with previous commits in this CVE series
There was a problem hiding this comment.
Choose a reason for hiding this comment
The reason will be displayed to describe this comment to others. Learn more.
🥌
jira LE-3201 cve CVE-2024-26976 Rebuild_History Non-Buildable kernel-rt-4.18.0-553.27.1.rt7.368.el8_10 commit-author Sean Christopherson <[email protected]> commit 3d75b8a Always flush the per-vCPU async #PF workqueue when a vCPU is clearing its completion queue, e.g. when a VM and all its vCPUs is being destroyed. KVM must ensure that none of its workqueue callbacks is running when the last reference to the KVM _module_ is put. Gifting a reference to the associated VM prevents the workqueue callback from dereferencing freed vCPU/VM memory, but does not prevent the KVM module from being unloaded before the callback completes. Drop the misguided VM refcount gifting, as calling kvm_put_kvm() from async_pf_execute() if kvm_put_kvm() flushes the async #PF workqueue will result in deadlock. async_pf_execute() can't return until kvm_put_kvm() finishes, and kvm_put_kvm() can't return until async_pf_execute() finishes: WARNING: CPU: 8 PID: 251 at virt/kvm/kvm_main.c:1435 kvm_put_kvm+0x2d/0x320 [kvm] Modules linked in: vhost_net vhost vhost_iotlb tap kvm_intel kvm irqbypass CPU: 8 PID: 251 Comm: kworker/8:1 Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Workqueue: events async_pf_execute [kvm] RIP: 0010:kvm_put_kvm+0x2d/0x320 [kvm] Call Trace: <TASK> async_pf_execute+0x198/0x260 [kvm] process_one_work+0x145/0x2d0 worker_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 </TASK> ---[ end trace 0000000000000000 ]--- INFO: task kworker/8:1:251 blocked for more than 120 seconds. Tainted: G W 6.6.0-rc1-e7af8d17224a-x86/gmem-vm #119 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:kworker/8:1 state:D stack:0 pid:251 ppid:2 flags:0x00004000 Workqueue: events async_pf_execute [kvm] Call Trace: <TASK> __schedule+0x33f/0xa40 schedule+0x53/0xc0 schedule_timeout+0x12a/0x140 __wait_for_common+0x8d/0x1d0 __flush_work.isra.0+0x19f/0x2c0 kvm_clear_async_pf_completion_queue+0x129/0x190 [kvm] kvm_arch_destroy_vm+0x78/0x1b0 [kvm] kvm_put_kvm+0x1c1/0x320 [kvm] async_pf_execute+0x198/0x260 [kvm] process_one_work+0x145/0x2d0 worker_thread+0x27e/0x3a0 kthread+0xba/0xe0 ret_from_fork+0x2d/0x50 ret_from_fork_asm+0x11/0x20 </TASK> If kvm_clear_async_pf_completion_queue() actually flushes the workqueue, then there's no need to gift async_pf_execute() a reference because all invocations of async_pf_execute() will be forced to complete before the vCPU and its VM are destroyed/freed. And that in turn fixes the module unloading bug as __fput() won't do module_put() on the last vCPU reference until the vCPU has been freed, e.g. if closing the vCPU file also puts the last reference to the KVM module. Note that kvm_check_async_pf_completion() may also take the work item off the completion queue and so also needs to flush the work queue, as the work will not be seen by kvm_clear_async_pf_completion_queue(). Waiting on the workqueue could theoretically delay a vCPU due to waiting for the work to complete, but that's a very, very small chance, and likely a very small delay. kvm_arch_async_page_present_queued() unconditionally makes a new request, i.e. will effectively delay entering the guest, so the remaining work is really just: trace_kvm_async_pf_completed(addr, cr2_or_gpa); __kvm_vcpu_wake_up(vcpu); mmput(mm); and mmput() can't drop the last reference to the page tables if the vCPU is still alive, i.e. the vCPU won't get stuck tearing down page tables. Add a helper to do the flushing, specifically to deal with "wakeup all" work items, as they aren't actually work items, i.e. are never placed in a workqueue. Trying to flush a bogus workqueue entry rightly makes __flush_work() complain (kudos to whoever added that sanity check). Note, commit 5f6de5c ("KVM: Prevent module exit until all VMs are freed") *tried* to fix the module refcounting issue by having VMs grab a reference to the module, but that only made the bug slightly harder to hit as it gave async_pf_execute() a bit more time to complete before the KVM module could be unloaded. Fixes: af585b9 ("KVM: Halt vcpu if page it tries to access is swapped out") Cc: [email protected] Cc: David Matlack <[email protected]> Reviewed-by: Xu Yilun <[email protected]> Reviewed-by: Vitaly Kuznetsov <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Sean Christopherson <[email protected]> (cherry picked from commit 3d75b8a) Signed-off-by: Jonathan Maple <[email protected]>
CVE-2023-4921
VULN-6731
Problem
https://www.cve.org/CVERecord?id=CVE-2023-4921
Solution
A single commit was identified as a fix for this issue: 8fc134fee27f2263988ae38920bc03da416b03d8
kABI check: omitted (unstable ABI of RT kernels)
Boot test: passed
See Specific tests for implied boot test passing.
Kselftests: passed relative
Methodology
A mix of
kernel-selftests-internal
and source-compiled tests were used:kernel-selftests-internal
:bpf
tests, except:bpf:test_kmod.sh
: takes very long time to finish and always fails anyway,bpf:test_progs
: unstable, can crash the machine,bpf:test_progs-no_alu32
: unstable, can crash the machine.Coverage (including tests skipped during execution)
android
,bpf
,breakpoints
,capabilities
,cgroup
,core
,cpu-hotplug
,cpufreq
,drivers/net/bonding
,drivers/net/team
,efivarfs
,exec
,filesystems
,firmware
,fpu
,ftrace
,futex
,gpio
,intel_pstate
,ipc
,kcmp
,kvm
,lib
,livepatch
,membarrier
,memfd
,memory-hotplug
,mount
,mqueue
,net
,net/forwarding
,net/mptcp
,netfilter
,nsfs
,proc
,pstore
,ptrace
,rseq
,rtc
,sgx
,sigaltstack
,size
,splice
,static_keys
,sync
,sysctl
,tc-testing
,tdx
,timens
,timers
,tpm2
,user
,vm
,x86
,zram
Reference
Four test runs were conducted on the reference kernel.
kselftests–mixed–ciqlts8_8-rt–run1.log
kselftests–mixed–ciqlts8_8-rt–run2.log
kselftests–mixed–ciqlts8_8-rt–run3.log
kselftests–mixed–ciqlts8_8-rt–run4.log
Patch
A single rest run was conducted on the patched kernel.
kselftests–mixed–ciqlts8_8-rt-CVE-2023-4921.log
Comparison
Overview of the results, reduced to the differences:
No differences in results occured which weren't present in the reference test set already.
One new unreliable test was identified:
bpf:test_tcpnotify_user
. The test may sometimes segfault, resulting in thefail
statusCompare with the successful run
Specific tests: passed
Bug replication
The bug can be replicated with the following commands, as mention in the commit's message:
The tests were performed on the referential and patched kernel.
Prerequisites
The
tc
commands above require the following kernel options to be enabled:CONFIG_NET_SCHED
,CONFIG_NET_SCH_INGRESS
,CONFIG_NET_SCH_QFQ
,CONFIG_NET_SCH_PLUG
,CONFIG_NET_CLS_BASIC
.All of them are enabled by default in the
configs/kernel-rt-4.18.0-x86_64.config
configuration file for the testedx86_64
platform.Reference
ciqlts8_8-rt
(838493098c124797753ec968c5e4c6e9996e9d90
)Bug replicated successfully. Kernel crashed and machine automatically rebooted, although no crash report was observed as in the non-RT LTS 8.8 version.
Full log:
bug-replication–ciqlts8_8-rt.log
Patch
Patch efficacy verified successfully. Repeating the steps doesn't result in a crash and the machine doesn't reboot.
Full log:
bug-replication–ciqlts8_8-rt-CVE-2023-4921.log
A warning can be observed
issued at sch_qfq.c. The work-conserving queue discipline is a qdisc which never leaves the outbound interface in idle unless the queue is empty, while non-work-conserving qdiscs may delay packets, for example to shape the traffic1. The
plug
qdisc, being the leaf in the hierarchical qdiscs configuration used, is non-work-conserving, as it is able to suspend the packet flow. Multiple types of qdiscs are apparently not designed to work with non-work-conserving child qdiscs and issue similar warnings onskb == NULL
condition: ets, hfsc, htb, drr. See also the message in b00355db3f88d96810a60011a30cfb2c3469409dand in 6d25d1dc76bf5943a5c1f4bb74d66d5eac58eb77, which includes
qfq
to the group aboveThe point is: the warning is related to the way the qdisc hierarchy has been defined in the bug replication script and not to the introduced changes.
Footnotes
1 https://tldp.org/HOWTO/Adv-Routing-HOWTO/lartc.qdisc.terminology.html