416baaa9-dc9f-4396-8d5f-8c081fb06d67CVE-2021-47546CVE-2021-47546
5.5 Medium
CVSS3
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.8 Medium
AI Score
Confidence
Low
0.0004 Low
EPSS
Percentile
5.1%
In the Linux kernel, the following vulnerability has been resolved:
ipv6: fix memory leak in fib6_rule_suppress
The kernel leaks memory when a fib rule is present in IPv6 nftables
firewall rules and a suppress_prefix rule is present in the IPv6 routing
rules (used by certain tools such as wg-quick). In such scenarios, every
incoming packet will leak an allocation in ip6_dst_cache slab cache.
After some hours of bpftrace-ing and source code reading, I tracked
down the issue to ca7a03c41753 (“ipv6: do not free rt if
FIB_LOOKUP_NOREF is set on suppress rule”).
The problem with that change is that the generic args->flags always have
FIB_LOOKUP_NOREF set1 but the IPv6-specific flag
RT6_LOOKUP_F_DST_NOREF might not be, leading to fib6_rule_suppress not
decreasing the refcount when needed.
How to reproduce:
- Add the following nftables rule to a prerouting chain:
meta nfproto ipv6 fib saddr . mark . iif oif missing drop
This can be done with:
sudo nft create table inet test
sudo nft create chain inet test test_chain ‘{ type filter hook prerouting priority filter + 10; policy accept; }’
sudo nft add rule inet test test_chain meta nfproto ipv6 fib saddr . mark . iif oif missing drop - Run:
sudo ip -6 rule add table main suppress_prefixlength 0 - Watch
sudo slabtop -o | grep ip6_dst_cacheto see memory usage increase
with every incoming ipv6 packet.
This patch exposes the protocol-specific flags to the protocol
specific suppress function, and check the protocol-specific flags
argument for RT6_LOOKUP_F_DST_NOREF instead of the generic
FIB_LOOKUP_NOREF when decreasing the refcount, like this.
Affected configurations
CNA Affected
[
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"include/net/fib_rules.h",
"net/core/fib_rules.c",
"net/ipv4/fib_rules.c",
"net/ipv6/fib6_rules.c"
],
"versions": [
{
"version": "ca7a03c41753",
"lessThan": "ee38eb8cf9a7",
"status": "affected",
"versionType": "git"
},
{
"version": "ca7a03c41753",
"lessThan": "209d35ee34e2",
"status": "affected",
"versionType": "git"
},
{
"version": "ca7a03c41753",
"lessThan": "8ef8a76a340e",
"status": "affected",
"versionType": "git"
},
{
"version": "ca7a03c41753",
"lessThan": "cdef485217d3",
"status": "affected",
"versionType": "git"
}
]
},
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "affected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"include/net/fib_rules.h",
"net/core/fib_rules.c",
"net/ipv4/fib_rules.c",
"net/ipv6/fib6_rules.c"
],
"versions": [
{
"version": "5.4",
"status": "affected"
},
{
"version": "0",
"lessThan": "5.4",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "5.4.164",
"lessThanOrEqual": "5.4.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "5.10.84",
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "5.15.7",
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"versionType": "custom"
},
{
"version": "5.16",
"lessThanOrEqual": "*",
"status": "unaffected",
"versionType": "original_commit_for_fix"
}
]
}
]Related
5.5 Medium
CVSS3
Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.8 Medium
AI Score
Confidence
Low
0.0004 Low
EPSS
Percentile
5.1%