In the Linux kernel, the following vulnerability has been resolved:
netfilter: nf_conntrack: fix crash due to removal of uninitialised entry
A crash in conntrack was reported while trying to unlink the conntrack entry from the hash bucket list: [exception RIP: __nf_ct_delete_from_lists+172] [..] #7 [ff539b5a2b043aa0] nf_ct_delete at ffffffffc124d421 [nf_conntrack] #8 [ff539b5a2b043ad0] nf_ct_gc_expired at ffffffffc124d999 [nf_conntrack] #9 [ff539b5a2b043ae0] __nf_conntrack_find_get at ffffffffc124efbc [nf_conntrack] [..]
The nf_conn struct is marked as allocated from slab but appears to be in a partially initialised state:
ct hlist pointer is garbage; looks like the ct hash value (hence crash). ct->status is equal to IPS_CONFIRMED|IPS_DYING, which is expected ct->timeout is 30000 (=30s), which is unexpected.
Everything else looks like normal udp conntrack entry. If we ignore ct->status and pretend its 0, the entry matches those that are newly allocated but not yet inserted into the hash:
If it were not for the presence of IPS_CONFIRMED, __nf_conntrack_find_get() would have skipped the entry.
Theory is that we did hit following race:
cpu x cpu y cpu z found entry E found entry E E is expired nf_ct_delete() return E to rcu slab init_conntrack E is re-inited, ct->status set to 0 reply tuplehash hnnode.pprev stores hash value.
cpu y found E right before it was deleted on cpu x. E is now re-inited on cpu z. cpu y was preempted before checking for expiry and/or confirm bit.
->refcnt set to 1
E now owned by skb
->timeout set to 30000
If cpu y were to resume now, it would observe E as expired but would skip E due to missing CONFIRMED bit.
nf_conntrack_confirm gets called
sets: ct->status |= CONFIRMED
This is wrong: E is not yet added
to hashtable.
cpu y resumes, it observes E as expired but CONFIRMED: nf_ct_expired() -> yes (ct->timeout is 30s) confirmed bit set.
cpu y will try to delete E from the hashtable: nf_ct_delete() -> set DYING bit __nf_ct_delete_from_lists
Even this scenario doesnt guarantee a crash: cpu z still holds the table bucket lock(s) so y blocks:
wait for spinlock held by z
CONFIRMED is set but there is no
guarantee ct will be added to hash:
chaintoolong or clash resolution
logic both skip the insert step.
reply hnnode.pprev still stores the
hash value.
unlocks spinlock
return NF_DROP
<unblocks, then
crashes on hlist_nulls_del_rcu pprev>
In case CPU z does insert the entry into the hashtable, cpu y will unlink E again right away but no crash occurs.
Without cpu y race, garbage hlist is of no consequence: ct refcnt remains at 1, eventually skb will be freed and E gets destroyed via: nf_conntrack_put -> nf_conntrack_destroy -> nf_ct_destroy.
To resolve this, move the IPS_CONFIRMED assignment after the table insertion but before the unlock.
Pablo points out that the confirm-bit-store could be reordered to happen before hlist add resp. the timeout fixup, so switch to set_bit and before_atomic memory barrier to prevent this.
It doesnt matter if other CPUs can observe a newly inserted entry right before the CONFIRMED bit was set:
Such event cannot be distinguished from above E is the old incarnation case: the entry will be skipped.
Also change nf_ct_should_gc() to first check the confirmed bit.
The gc sequence is:
nf_ct_should_gc() is thus called only for entries that already failed an expiry check. After this patch, once the confirmed bit check pas —truncated—
Name | Vendor | Start Version | End Version |
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Linux | Ubuntu | plucky | * |
Linux | Ubuntu | upstream | * |
Linux-allwinner-5.19 | Ubuntu | jammy | * |
Linux-allwinner-5.19 | Ubuntu | upstream | * |
Linux-aws | Ubuntu | devel | * |
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Linux-aws-5.11 | Ubuntu | esm-infra/focal | * |
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Linux-aws-5.11 | Ubuntu | upstream | * |
Linux-aws-5.13 | Ubuntu | esm-infra/focal | * |
Linux-aws-5.13 | Ubuntu | focal | * |
Linux-aws-5.13 | Ubuntu | upstream | * |
Linux-aws-5.15 | Ubuntu | upstream | * |
Linux-aws-5.19 | Ubuntu | jammy | * |
Linux-aws-5.19 | Ubuntu | upstream | * |
Linux-aws-5.3 | Ubuntu | bionic | * |
Linux-aws-5.3 | Ubuntu | esm-infra/bionic | * |
Linux-aws-5.3 | Ubuntu | upstream | * |
Linux-aws-5.4 | Ubuntu | upstream | * |
Linux-aws-5.8 | Ubuntu | esm-infra/focal | * |
Linux-aws-5.8 | Ubuntu | focal | * |
Linux-aws-5.8 | Ubuntu | upstream | * |
Linux-aws-6.14 | Ubuntu | noble | * |
Linux-aws-6.14 | Ubuntu | upstream | * |
Linux-aws-6.2 | Ubuntu | jammy | * |
Linux-aws-6.2 | Ubuntu | upstream | * |
Linux-aws-6.5 | Ubuntu | jammy | * |
Linux-aws-6.5 | Ubuntu | upstream | * |
Linux-aws-6.8 | Ubuntu | jammy | * |
Linux-aws-6.8 | Ubuntu | upstream | * |
Linux-aws-fips | Ubuntu | trusty | * |
Linux-aws-fips | Ubuntu | upstream | * |
Linux-aws-fips | Ubuntu | xenial | * |
Linux-aws-hwe | Ubuntu | upstream | * |
Linux-azure | Ubuntu | bionic | * |
Linux-azure | Ubuntu | devel | * |
Linux-azure | Ubuntu | esm-infra/bionic | * |
Linux-azure | Ubuntu | noble | * |
Linux-azure | Ubuntu | plucky | * |
Linux-azure | Ubuntu | upstream | * |
Linux-azure-4.15 | Ubuntu | upstream | * |
Linux-azure-5.11 | Ubuntu | esm-infra/focal | * |
Linux-azure-5.11 | Ubuntu | focal | * |
Linux-azure-5.11 | Ubuntu | upstream | * |
Linux-azure-5.13 | Ubuntu | esm-infra/focal | * |
Linux-azure-5.13 | Ubuntu | focal | * |
Linux-azure-5.13 | Ubuntu | upstream | * |
Linux-azure-5.15 | Ubuntu | upstream | * |
Linux-azure-5.19 | Ubuntu | jammy | * |
Linux-azure-5.19 | Ubuntu | upstream | * |
Linux-azure-5.3 | Ubuntu | bionic | * |
Linux-azure-5.3 | Ubuntu | esm-infra/bionic | * |
Linux-azure-5.3 | Ubuntu | upstream | * |
Linux-azure-5.4 | Ubuntu | upstream | * |
Linux-azure-5.8 | Ubuntu | esm-infra/focal | * |
Linux-azure-5.8 | Ubuntu | focal | * |
Linux-azure-5.8 | Ubuntu | upstream | * |
Linux-azure-6.11 | Ubuntu | noble | * |
Linux-azure-6.11 | Ubuntu | upstream | * |
Linux-azure-6.2 | Ubuntu | jammy | * |
Linux-azure-6.2 | Ubuntu | upstream | * |
Linux-azure-6.5 | Ubuntu | jammy | * |
Linux-azure-6.5 | Ubuntu | upstream | * |
Linux-azure-6.8 | Ubuntu | jammy | * |
Linux-azure-6.8 | Ubuntu | upstream | * |
Linux-azure-edge | Ubuntu | bionic | * |
Linux-azure-edge | Ubuntu | esm-infra/bionic | * |
Linux-azure-edge | Ubuntu | upstream | * |
Linux-azure-fde | Ubuntu | esm-infra/focal | * |
Linux-azure-fde | Ubuntu | focal | * |
Linux-azure-fde | Ubuntu | upstream | * |
Linux-azure-fde-5.15 | Ubuntu | upstream | * |
Linux-azure-fde-5.19 | Ubuntu | jammy | * |
Linux-azure-fde-5.19 | Ubuntu | upstream | * |
Linux-azure-fde-6.2 | Ubuntu | jammy | * |
Linux-azure-fde-6.2 | Ubuntu | upstream | * |
Linux-azure-fips | Ubuntu | trusty | * |
Linux-azure-fips | Ubuntu | upstream | * |
Linux-azure-fips | Ubuntu | xenial | * |
Linux-azure-nvidia | Ubuntu | noble | * |
Linux-azure-nvidia | Ubuntu | upstream | * |
Linux-bluefield | Ubuntu | upstream | * |
Linux-fips | Ubuntu | upstream | * |
Linux-gcp | Ubuntu | bionic | * |
Linux-gcp | Ubuntu | devel | * |
Linux-gcp | Ubuntu | esm-infra/bionic | * |
Linux-gcp | Ubuntu | noble | * |
Linux-gcp | Ubuntu | plucky | * |
Linux-gcp | Ubuntu | upstream | * |
Linux-gcp-4.15 | Ubuntu | upstream | * |
Linux-gcp-5.11 | Ubuntu | esm-infra/focal | * |
Linux-gcp-5.11 | Ubuntu | focal | * |
Linux-gcp-5.11 | Ubuntu | upstream | * |
Linux-gcp-5.13 | Ubuntu | esm-infra/focal | * |
Linux-gcp-5.13 | Ubuntu | focal | * |
Linux-gcp-5.13 | Ubuntu | upstream | * |
Linux-gcp-5.15 | Ubuntu | upstream | * |
Linux-gcp-5.19 | Ubuntu | jammy | * |
Linux-gcp-5.19 | Ubuntu | upstream | * |
Linux-gcp-5.3 | Ubuntu | bionic | * |
Linux-gcp-5.3 | Ubuntu | esm-infra/bionic | * |
Linux-gcp-5.3 | Ubuntu | upstream | * |
Linux-gcp-5.4 | Ubuntu | upstream | * |
Linux-gcp-5.8 | Ubuntu | esm-infra/focal | * |
Linux-gcp-5.8 | Ubuntu | focal | * |
Linux-gcp-5.8 | Ubuntu | upstream | * |
Linux-gcp-6.11 | Ubuntu | noble | * |
Linux-gcp-6.11 | Ubuntu | upstream | * |
Linux-gcp-6.14 | Ubuntu | noble | * |
Linux-gcp-6.14 | Ubuntu | upstream | * |
Linux-gcp-6.2 | Ubuntu | jammy | * |
Linux-gcp-6.2 | Ubuntu | upstream | * |
Linux-gcp-6.5 | Ubuntu | jammy | * |
Linux-gcp-6.5 | Ubuntu | upstream | * |
Linux-gcp-6.8 | Ubuntu | jammy | * |
Linux-gcp-6.8 | Ubuntu | upstream | * |
Linux-gcp-fips | Ubuntu | trusty | * |
Linux-gcp-fips | Ubuntu | upstream | * |
Linux-gcp-fips | Ubuntu | xenial | * |
Linux-gke | Ubuntu | esm-infra/focal | * |
Linux-gke | Ubuntu | focal | * |
Linux-gke | Ubuntu | noble | * |
Linux-gke | Ubuntu | upstream | * |
Linux-gke | Ubuntu | xenial | * |
Linux-gke-4.15 | Ubuntu | bionic | * |
Linux-gke-4.15 | Ubuntu | esm-infra/bionic | * |
Linux-gke-4.15 | Ubuntu | upstream | * |
Linux-gke-5.15 | Ubuntu | esm-infra/focal | * |
Linux-gke-5.15 | Ubuntu | focal | * |
Linux-gke-5.15 | Ubuntu | upstream | * |
Linux-gke-5.4 | Ubuntu | bionic | * |
Linux-gke-5.4 | Ubuntu | esm-infra/bionic | * |
Linux-gke-5.4 | Ubuntu | upstream | * |
Linux-gkeop | Ubuntu | esm-infra/focal | * |
Linux-gkeop | Ubuntu | focal | * |
Linux-gkeop | Ubuntu | noble | * |
Linux-gkeop | Ubuntu | upstream | * |
Linux-gkeop-5.15 | Ubuntu | esm-infra/focal | * |
Linux-gkeop-5.15 | Ubuntu | focal | * |
Linux-gkeop-5.15 | Ubuntu | upstream | * |
Linux-gkeop-5.4 | Ubuntu | bionic | * |
Linux-gkeop-5.4 | Ubuntu | esm-infra/bionic | * |
Linux-gkeop-5.4 | Ubuntu | upstream | * |
Linux-hwe | Ubuntu | bionic | * |
Linux-hwe | Ubuntu | esm-infra/bionic | * |
Linux-hwe | Ubuntu | upstream | * |
Linux-hwe-5.11 | Ubuntu | esm-infra/focal | * |
Linux-hwe-5.11 | Ubuntu | focal | * |
Linux-hwe-5.11 | Ubuntu | upstream | * |
Linux-hwe-5.13 | Ubuntu | esm-infra/focal | * |
Linux-hwe-5.13 | Ubuntu | focal | * |
Linux-hwe-5.13 | Ubuntu | upstream | * |
Linux-hwe-5.15 | Ubuntu | upstream | * |
Linux-hwe-5.19 | Ubuntu | jammy | * |
Linux-hwe-5.19 | Ubuntu | upstream | * |
Linux-hwe-5.4 | Ubuntu | upstream | * |
Linux-hwe-5.8 | Ubuntu | esm-infra/focal | * |
Linux-hwe-5.8 | Ubuntu | focal | * |
Linux-hwe-5.8 | Ubuntu | upstream | * |
Linux-hwe-6.11 | Ubuntu | noble | * |
Linux-hwe-6.11 | Ubuntu | upstream | * |
Linux-hwe-6.14 | Ubuntu | noble | * |
Linux-hwe-6.14 | Ubuntu | upstream | * |
Linux-hwe-6.2 | Ubuntu | jammy | * |
Linux-hwe-6.2 | Ubuntu | upstream | * |
Linux-hwe-6.5 | Ubuntu | jammy | * |
Linux-hwe-6.5 | Ubuntu | upstream | * |
Linux-hwe-6.8 | Ubuntu | jammy | * |
Linux-hwe-6.8 | Ubuntu | upstream | * |
Linux-hwe-edge | Ubuntu | bionic | * |
Linux-hwe-edge | Ubuntu | esm-infra/bionic | * |
Linux-hwe-edge | Ubuntu | esm-infra/xenial | * |
Linux-hwe-edge | Ubuntu | upstream | * |
Linux-hwe-edge | Ubuntu | xenial | * |
Linux-ibm | Ubuntu | noble | * |
Linux-ibm | Ubuntu | upstream | * |
Linux-ibm-5.15 | Ubuntu | upstream | * |
Linux-ibm-5.4 | Ubuntu | upstream | * |
Linux-ibm-6.8 | Ubuntu | jammy | * |
Linux-ibm-6.8 | Ubuntu | upstream | * |
Linux-intel | Ubuntu | noble | * |
Linux-intel | Ubuntu | upstream | * |
Linux-intel-5.13 | Ubuntu | esm-infra/focal | * |
Linux-intel-5.13 | Ubuntu | focal | * |
Linux-intel-5.13 | Ubuntu | upstream | * |
Linux-intel-iot-realtime | Ubuntu | jammy | * |
Linux-intel-iot-realtime | Ubuntu | upstream | * |
Linux-intel-iotg | Ubuntu | upstream | * |
Linux-intel-iotg-5.15 | Ubuntu | upstream | * |
Linux-iot | Ubuntu | upstream | * |
Linux-kvm | Ubuntu | upstream | * |
Linux-lowlatency | Ubuntu | noble | * |
Linux-lowlatency | Ubuntu | upstream | * |
Linux-lowlatency-hwe-5.15 | Ubuntu | upstream | * |
Linux-lowlatency-hwe-5.19 | Ubuntu | jammy | * |
Linux-lowlatency-hwe-5.19 | Ubuntu | upstream | * |
Linux-lowlatency-hwe-6.11 | Ubuntu | noble | * |
Linux-lowlatency-hwe-6.11 | Ubuntu | upstream | * |
Linux-lowlatency-hwe-6.2 | Ubuntu | jammy | * |
Linux-lowlatency-hwe-6.2 | Ubuntu | upstream | * |
Linux-lowlatency-hwe-6.5 | Ubuntu | jammy | * |
Linux-lowlatency-hwe-6.5 | Ubuntu | upstream | * |
Linux-lowlatency-hwe-6.8 | Ubuntu | jammy | * |
Linux-lowlatency-hwe-6.8 | Ubuntu | upstream | * |
Linux-lts-xenial | Ubuntu | upstream | * |
Linux-nvidia | Ubuntu | noble | * |
Linux-nvidia | Ubuntu | upstream | * |
Linux-nvidia-6.11 | Ubuntu | noble | * |
Linux-nvidia-6.11 | Ubuntu | upstream | * |
Linux-nvidia-6.2 | Ubuntu | jammy | * |
Linux-nvidia-6.2 | Ubuntu | upstream | * |
Linux-nvidia-6.5 | Ubuntu | jammy | * |
Linux-nvidia-6.5 | Ubuntu | upstream | * |
Linux-nvidia-6.8 | Ubuntu | jammy | * |
Linux-nvidia-6.8 | Ubuntu | upstream | * |
Linux-nvidia-lowlatency | Ubuntu | noble | * |
Linux-nvidia-lowlatency | Ubuntu | upstream | * |
Linux-nvidia-tegra | Ubuntu | noble | * |
Linux-nvidia-tegra | Ubuntu | upstream | * |
Linux-nvidia-tegra-5.15 | Ubuntu | upstream | * |
Linux-nvidia-tegra-igx | Ubuntu | upstream | * |
Linux-oem | Ubuntu | bionic | * |
Linux-oem | Ubuntu | esm-infra/bionic | * |
Linux-oem | Ubuntu | upstream | * |
Linux-oem | Ubuntu | xenial | * |
Linux-oem-5.10 | Ubuntu | esm-infra/focal | * |
Linux-oem-5.10 | Ubuntu | focal | * |
Linux-oem-5.10 | Ubuntu | upstream | * |
Linux-oem-5.13 | Ubuntu | esm-infra/focal | * |
Linux-oem-5.13 | Ubuntu | focal | * |
Linux-oem-5.13 | Ubuntu | upstream | * |
Linux-oem-5.14 | Ubuntu | esm-infra/focal | * |
Linux-oem-5.14 | Ubuntu | focal | * |
Linux-oem-5.14 | Ubuntu | upstream | * |
Linux-oem-5.17 | Ubuntu | jammy | * |
Linux-oem-5.17 | Ubuntu | upstream | * |
Linux-oem-5.6 | Ubuntu | esm-infra/focal | * |
Linux-oem-5.6 | Ubuntu | focal | * |
Linux-oem-5.6 | Ubuntu | upstream | * |
Linux-oem-6.0 | Ubuntu | jammy | * |
Linux-oem-6.0 | Ubuntu | upstream | * |
Linux-oem-6.1 | Ubuntu | jammy | * |
Linux-oem-6.1 | Ubuntu | upstream | * |
Linux-oem-6.11 | Ubuntu | noble | * |
Linux-oem-6.11 | Ubuntu | upstream | * |
Linux-oem-6.14 | Ubuntu | noble | * |
Linux-oem-6.14 | Ubuntu | upstream | * |
Linux-oem-6.5 | Ubuntu | jammy | * |
Linux-oem-6.5 | Ubuntu | upstream | * |
Linux-oem-6.8 | Ubuntu | noble | * |
Linux-oem-6.8 | Ubuntu | upstream | * |
Linux-oracle | Ubuntu | devel | * |
Linux-oracle | Ubuntu | noble | * |
Linux-oracle | Ubuntu | plucky | * |
Linux-oracle | Ubuntu | upstream | * |
Linux-oracle-5.0 | Ubuntu | bionic | * |
Linux-oracle-5.0 | Ubuntu | esm-infra/bionic | * |
Linux-oracle-5.0 | Ubuntu | upstream | * |
Linux-oracle-5.11 | Ubuntu | esm-infra/focal | * |
Linux-oracle-5.11 | Ubuntu | focal | * |
Linux-oracle-5.11 | Ubuntu | upstream | * |
Linux-oracle-5.13 | Ubuntu | esm-infra/focal | * |
Linux-oracle-5.13 | Ubuntu | focal | * |
Linux-oracle-5.13 | Ubuntu | upstream | * |
Linux-oracle-5.15 | Ubuntu | upstream | * |
Linux-oracle-5.3 | Ubuntu | bionic | * |
Linux-oracle-5.3 | Ubuntu | esm-infra/bionic | * |
Linux-oracle-5.3 | Ubuntu | upstream | * |
Linux-oracle-5.4 | Ubuntu | upstream | * |
Linux-oracle-5.8 | Ubuntu | esm-infra/focal | * |
Linux-oracle-5.8 | Ubuntu | focal | * |
Linux-oracle-5.8 | Ubuntu | upstream | * |
Linux-oracle-6.14 | Ubuntu | noble | * |
Linux-oracle-6.14 | Ubuntu | upstream | * |
Linux-oracle-6.5 | Ubuntu | jammy | * |
Linux-oracle-6.5 | Ubuntu | upstream | * |
Linux-oracle-6.8 | Ubuntu | jammy | * |
Linux-oracle-6.8 | Ubuntu | upstream | * |
Linux-raspi | Ubuntu | devel | * |
Linux-raspi | Ubuntu | noble | * |
Linux-raspi | Ubuntu | plucky | * |
Linux-raspi | Ubuntu | upstream | * |
Linux-raspi-5.4 | Ubuntu | upstream | * |
Linux-raspi-realtime | Ubuntu | noble | * |
Linux-raspi-realtime | Ubuntu | realtime/noble | * |
Linux-raspi-realtime | Ubuntu | upstream | * |
Linux-raspi2 | Ubuntu | bionic | * |
Linux-raspi2 | Ubuntu | esm-infra/focal | * |
Linux-raspi2 | Ubuntu | focal | * |
Linux-raspi2 | Ubuntu | upstream | * |
Linux-raspi2 | Ubuntu | xenial | * |
Linux-realtime | Ubuntu | devel | * |
Linux-realtime | Ubuntu | jammy | * |
Linux-realtime | Ubuntu | noble | * |
Linux-realtime | Ubuntu | plucky | * |
Linux-realtime | Ubuntu | realtime/noble | * |
Linux-realtime | Ubuntu | upstream | * |
Linux-riscv | Ubuntu | devel | * |
Linux-riscv | Ubuntu | esm-infra/focal | * |
Linux-riscv | Ubuntu | focal | * |
Linux-riscv | Ubuntu | jammy | * |
Linux-riscv | Ubuntu | noble | * |
Linux-riscv | Ubuntu | plucky | * |
Linux-riscv | Ubuntu | upstream | * |
Linux-riscv-5.11 | Ubuntu | esm-infra/focal | * |
Linux-riscv-5.11 | Ubuntu | focal | * |
Linux-riscv-5.11 | Ubuntu | upstream | * |
Linux-riscv-5.15 | Ubuntu | upstream | * |
Linux-riscv-5.19 | Ubuntu | jammy | * |
Linux-riscv-5.19 | Ubuntu | upstream | * |
Linux-riscv-5.8 | Ubuntu | esm-infra/focal | * |
Linux-riscv-5.8 | Ubuntu | focal | * |
Linux-riscv-5.8 | Ubuntu | upstream | * |
Linux-riscv-6.14 | Ubuntu | noble | * |
Linux-riscv-6.14 | Ubuntu | upstream | * |
Linux-riscv-6.5 | Ubuntu | jammy | * |
Linux-riscv-6.5 | Ubuntu | upstream | * |
Linux-riscv-6.8 | Ubuntu | jammy | * |
Linux-riscv-6.8 | Ubuntu | upstream | * |
Linux-starfive-5.19 | Ubuntu | jammy | * |
Linux-starfive-5.19 | Ubuntu | upstream | * |
Linux-starfive-6.2 | Ubuntu | jammy | * |
Linux-starfive-6.2 | Ubuntu | upstream | * |
Linux-starfive-6.5 | Ubuntu | jammy | * |
Linux-starfive-6.5 | Ubuntu | upstream | * |
Linux-xilinx-zynqmp | Ubuntu | upstream | * |