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:
sudo slabtop -o | grep ip6_dst_cache
to see memory usage increaseThis 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.
[
{
"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"
}
]
}
]