Re: [PATCH net 5/5] net: restrict message_cost and message_burst to non-negative values
From: Fernando Fernandez Mancera
Date: Fri Oct 23 2026 - 08:57:43 EST
On 10/23/26 2:19 PM, Joel Granados wrote:
On Fri, Oct 23, 2026 at 05:13:31PM +0800, Jiayuan Chen wrote:
net.core.message_cost and net.core.message_burst feed the interval and
burst of net_ratelimit_state, but neither has a lower bound:
message_burst uses plain proc_dointvec, and message_cost uses
proc_dointvec_jiffies, which happily stores -1 second as -HZ jiffies.
Since commit a940d145cc38 ("ratelimit: Warn if ->interval or ->burst are
negative"), ___ratelimit() splats on such values, so the next
net_ratelimit() caller warns, e.g. a martian source log:
Negative interval (-250) or burst (10): Uninitialized ratelimit_state structure?
WARNING: lib/ratelimit.c:43 at ___ratelimit+0x56e/0x960, CPU#1: ping/3218
RIP: 0010:___ratelimit+0x578/0x960
Call Trace:
<IRQ>
net_ratelimit+0x1c/0x30
ip_handle_martian_source+0x1bb/0x340
ip_route_input_slow+0x1057/0x3650
ip_route_input_noref+0x104/0x260
arp_process+0x109b/0x2510
arp_rcv+0x381/0x460
__netif_receive_skb_one_core+0x173/0x1c0
__netif_receive_skb+0x21/0x150
process_backlog+0x37e/0x1200
__napi_poll.constprop.0+0xa5/0x5e0
net_rx_action+0x4c0/0xf70
handle_softirqs+0x204/0x9b0
__do_softirq+0x10/0x18
do_softirq.part.0+0x49/0xd0
</IRQ>
Negative values never meant anything here: ___ratelimit() treats them
like 0, and 0 already expresses both "no limit" (interval) and
"suppress everything" (burst).
Reject them at write time. message_burst can simply use
proc_dointvec_minmax with extra1 = 0. proc_dointvec_jiffies ignores
extra1/extra2, so give message_cost a small handler that parses into a
temporary and only stores the value if it is not negative.
Fixes: a940d145cc38 ("ratelimit: Warn if ->interval or ->burst are negative")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>
---
net/core/sysctl_net_core.c | 21 +++++++++++++++++++--
1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 473c162736d6..8146ed819695 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -378,6 +378,22 @@ static int proc_do_skb_defer_max(const struct ctl_table *table, int write,
return ret;
}
+static int proc_do_message_cost(const struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ int ret, interval = READ_ONCE(*(int *)table->data);
+ struct ctl_table tmp = *table;
+
+ tmp.data = &interval;
+ ret = proc_dointvec_jiffies(&tmp, write, buffer, lenp, ppos);
+ if (write && !ret) {
+ if (interval < 0)
+ return -EINVAL;
+ WRITE_ONCE(*(int *)table->data, interval);
+ }
+ return ret;
+}
+
#ifdef CONFIG_BPF_JIT
static int proc_dointvec_minmax_bpf_enable(const struct ctl_table *table, int write,
void *buffer, size_t *lenp,
@@ -544,14 +560,15 @@ static struct ctl_table net_core_table[] = {
.data = &net_ratelimit_state.interval,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec_jiffies,
+ .proc_handler = proc_do_message_cost,
},
{
.procname = "message_burst",
.data = &net_ratelimit_state.burst,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = proc_dointvec_minmax,
+ .extra1 = SYSCTL_ZERO,
},
#ifdef CONFIG_RPS
{
--
2.43.0
I would prefer something like this [1] (not tested and not compiled).
This is more in line with the patterns inside the jiffies.c file. I put
SYSCTL_ZERO there, but I have a doubt if you actually need SYSCTL_ONE.
If the interval variable can be zero, then leave it as SYSCTL_ZERO, but
if it cant be zero and can be one the use SYSCTL_ONE
FWIW, I also like this solution and indeed we can convert other users in the future.
About SYSCTL_ZERO, I believe it is the right choice. AFAIU, it just disables limiting.
Thanks,
Fernando.
best
[1]
diff --git i/include/linux/jiffies.h w/include/linux/jiffies.h
index bbd57061802c..288ba81ed53e 100644
--- i/include/linux/jiffies.h
+++ w/include/linux/jiffies.h
@@ -646,6 +646,8 @@ extern unsigned long nsecs_to_jiffies(u64 n);
struct ctl_table;
int proc_dointvec_jiffies(const struct ctl_table *table, int dir, void *buffer,
size_t *lenp, loff_t *ppos);
+int proc_dointvec_jiffies_minmax(const struct ctl_table *table, int dir, void *buffer,
+ size_t *lenp, loff_t *ppos);
int proc_dointvec_ms_jiffies_minmax(const struct ctl_table *table, int dir,
void *buffer, size_t *lenp, loff_t *ppos);
int proc_dointvec_userhz_jiffies(const struct ctl_table *table, int dir,
diff --git i/kernel/time/jiffies.c w/kernel/time/jiffies.c
index 9b3487d40cd6..cf91996fe4e3 100644
--- i/kernel/time/jiffies.c
+++ w/kernel/time/jiffies.c
@@ -165,6 +165,14 @@ static int do_proc_int_conv_jiffies(bool *negp, ulong *u_ptr, int *k_ptr,
sysctl_u2k_int_conv_hz, sysctl_k2u_int_conv_hz);
}
+static int do_proc_int_conv_jiffies_minmax(bool *negp, ulong *u_ptr, int *k_ptr,
+ int dir, const struct ctl_table *tbl)
+{
+ return proc_int_conv(negp, u_ptr, k_ptr, dir, tbl, true,
+ sysctl_u2k_int_conv_hz, sysctl_k2u_int_conv_hz);
+}
+
+
static int do_proc_int_conv_userhz_jiffies(bool *negp, ulong *u_ptr,
int *k_ptr, int dir,
const struct ctl_table *tbl)
@@ -263,6 +271,15 @@ int proc_dointvec_jiffies(const struct ctl_table *table, int dir,
}
EXPORT_SYMBOL(proc_dointvec_jiffies);
+int proc_dointvec_jiffies_minmax(const struct ctl_table *table, int dir,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ return proc_dointvec_conv(table, dir, buffer, lenp, ppos,
+ do_proc_int_conv_jiffies_minmax);
+}
+EXPORT_SYMBOL(proc_dointvec_jiffies);
+
+
/**
* proc_dointvec_userhz_jiffies - read a vector of integers as 1/USER_HZ seconds
* @table: the sysctl table
diff --git i/net/core/sysctl_net_core.c w/net/core/sysctl_net_core.c
index eb35da3556f4..7226697bf7c1 100644
--- i/net/core/sysctl_net_core.c
+++ w/net/core/sysctl_net_core.c
@@ -538,7 +538,8 @@ static struct ctl_table net_core_table[] = {
.data = &net_ratelimit_state.interval,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec_jiffies,
+ .proc_handler = proc_dointvec_jiffies_minmax,
+ .extra1 = SYSCTL_ZERO,
},
{
.procname = "message_burst",