CVE-2021-47452

published 2024-05-22

CVE-2021-47452: In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: skip netdev events generated on netns removal syzbot reported…

Priority P4 19 medium 5.5 CVSS 3.1

AV L AC L PR L UI N S U C N I N A H

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_tables: skip netdev events generated on netns removal

syzbot reported following (harmless) WARN:

WARNING: CPU: 1 PID: 2648 at net/netfilter/core.c:468
nft_netdev_unregister_hooks net/netfilter/nf_tables_api.c:230 [inline]
nf_tables_unregister_hook include/net/netfilter/nf_tables.h:1090 [inline]
__nft_release_basechain+0x138/0x640 net/netfilter/nf_tables_api.c:9524
nft_netdev_event net/netfilter/nft_chain_filter.c:351 [inline]
nf_tables_netdev_event+0x521/0x8a0 net/netfilter/nft_chain_filter.c:382

reproducer:
unshare -n bash -c 'ip link add br0 type bridge; nft add table netdev t ; \
nft add chain netdev t ingress \{ type filter hook ingress device "br0" \
priority 0\; policy drop\; \}'

Problem is that when netns device exit hooks create the UNREGISTER
event, the .pre_exit hook for nf_tables core has already removed the
base hook. Notifier attempts to do this again.

The need to do base hook unregister unconditionally was needed in the past,
because notifier was last stage where reg->dev dereference was safe.

Now that nf_tables does the hook removal in .pre_exit, this isn't
needed anymore.

Affected

16 ranges

Vendor	Product	Version range	Fixed in
debian	linux	< linux 5.14.16-1 (bookworm)	linux 5.14.16-1 (bookworm)
linux	linux	—	—
linux	linux	—	—
linux	linux	—	—
linux	linux	>= 5.10.17 < 5.11	5.11
linux	linux	>= 5.4.99 < 5.5	5.5
linux	linux	>= 767d1216bff82507c945e92fe719dff2083bb2f4 < 90c7c58aa2bd02c65a4c63b7dfe0b16eab12cf9f	90c7c58aa2bd02c65a4c63b7dfe0b16eab12cf9f
linux	linux	>= 767d1216bff82507c945e92fe719dff2083bb2f4 < 68a3765c659f809dcaac20030853a054646eb739	68a3765c659f809dcaac20030853a054646eb739
linux	linux_kernel	—	—
linux	linux_kernel	—	—
linux	linux_kernel	>= 0 < 5.14.16-1	5.14.16-1
linux	linux_kernel	>= 0 < 5.14.16-1	5.14.16-1
linux	linux_kernel	>= 0 < 5.14.16-1	5.14.16-1
linux	linux_kernel	>= 5.10.17 < 5.11	5.11
linux	linux_kernel	>= 5.11.1 < 5.14.15	5.14.15
linux	linux_kernel	>= 5.4.99 < 5.5	5.5

CVSS provenance

nvd v3.1 5.5 MEDIUM CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

osv 5.5 MEDIUM

vendor_debian 5.5 MEDIUM

vendor_redhat 5.5 MEDIUM

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