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netfilter: conntrack: Bound nf_conntrack sysctl writes

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[ Upstream commit 8b6861390ffee6b8ed78b9395e3776c16fec6579 ]

nf_conntrack_max and nf_conntrack_expect_max sysctls were authorized to
be written any negative value, which would then be stored in the
unsigned int variables nf_conntrack_max and nf_ct_expect_max variables.

While the do_proc_dointvec_conv function is supposed to limit writing
handled by proc_dointvec proc_handler to INT_MAX. Such a negative value
being written in an unsigned int leads to a very high value, exceeding
this limit.

Moreover, the nf_conntrack_expect_max sysctl documentation specifies the
minimum value is 1.

The proc_handlers have thus been updated to proc_dointvec_minmax in
order to specify the following write bounds :

* Bound nf_conntrack_max sysctl writings between SYSCTL_ZERO
  and SYSCTL_INT_MAX.

* Bound nf_conntrack_expect_max sysctl writings between SYSCTL_ONE
  and SYSCTL_INT_MAX as defined in the sysctl documentation.

With this patch applied, sysctl writes outside the defined in the bound
will thus lead to a write error :

```
sysctl -w net.netfilter.nf_conntrack_expect_max=-1
sysctl: setting key "net.netfilter.nf_conntrack_expect_max": Invalid argument
```

Signed-off-by: Nicolas Bouchinet <nicolas.bouchinet@ssi.gouv.fr>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Nicolas Bouchinet
2025-01-29 18:06:30 +01:00
committed by Greg Kroah-Hartman
parent da36c3ad7c
commit 89947eea8f
1 changed files with 9 additions and 3 deletions
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12
net/netfilter/nf_conntrack_standalone.c
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@@ -621,7 +621,9 @@ static struct ctl_table nf_ct_sysctl_table[] = {
.data = &nf_conntrack_max,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_INT_MAX,
},
[NF_SYSCTL_CT_COUNT] = {
.procname = "nf_conntrack_count",
@@ -657,7 +659,9 @@ static struct ctl_table nf_ct_sysctl_table[] = {
.data = &nf_ct_expect_max,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ONE,
.extra2 = SYSCTL_INT_MAX,
},
[NF_SYSCTL_CT_ACCT] = {
.procname = "nf_conntrack_acct",
@@ -951,7 +955,9 @@ static struct ctl_table nf_ct_netfilter_table[] = {
.data = &nf_conntrack_max,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_INT_MAX,
},
{ }
};