[PATCH net v2 5/5] net: restrict message_cost and message_burst to non-negative values

[Jiayuan Chen]

net.core.message_cost and net.core.message_burst feed the interval and
burst of net_ratelimit_state, but neither rejects negative values:
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: 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 has no
minmax variant, so add proc_dointvec_jiffies_minmax(), mirroring
proc_dointvec_ms_jiffies_minmax(), and use it for message_cost with
extra1 = 0. Note that like the ms variant, extra1/extra2 are compared
against the converted jiffies value.

Fixes: a940d145cc38 ("ratelimit: Warn if ->interval or ->burst are negative")
Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Joel Granados <joel.granados@xxxxxxxxxx>
Signed-off-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxx>
---
 include/linux/jiffies.h    |  2 ++
 kernel/time/jiffies.c      | 40 ++++++++++++++++++++++++++++++++++++++
 net/core/sysctl_net_core.c |  6 ++++--
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index bbd57061802cd..de12920f8e94b 100644
--- a/include/linux/jiffies.h
+++ b/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 a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index 9b3487d40cd6a..22a70caa58bc1 100644
--- a/kernel/time/jiffies.c
+++ b/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)
@@ -213,6 +221,13 @@ static int do_proc_int_conv_jiffies(bool *negp, ulong *u_ptr, int *k_ptr,
 	return -ENOSYS;
 }
 
+static int do_proc_int_conv_jiffies_minmax(bool *negp, ulong *u_ptr,
+					   int *k_ptr, int dir,
+					   const struct ctl_table *tbl)
+{
+	return -ENOSYS;
+}
+
 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 +278,31 @@ int proc_dointvec_jiffies(const struct ctl_table *table, int dir,
 }
 EXPORT_SYMBOL(proc_dointvec_jiffies);
 
+/**
+ * proc_dointvec_jiffies_minmax - read a vector of integers as seconds with min/max values
+ * @table: the sysctl table
+ * @dir: %TRUE if this is a write to the sysctl file
+ * @buffer: the user buffer
+ * @lenp: the size of the user buffer
+ * @ppos: file position
+ *
+ * Reads/writes up to table->maxlen/sizeof(unsigned int) integer
+ * values from/to the user buffer, treated as an ASCII string.
+ * The values read are assumed to be in seconds, and are converted into
+ * jiffies. The converted values are checked against the optional
+ * table->extra1 (min) and table->extra2 (max) bounds, in jiffies;
+ * a value outside the range is rejected with -EINVAL.
+ *
+ * Returns 0 on success.
+ */
+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_minmax);
+
 /**
  * proc_dointvec_userhz_jiffies - read a vector of integers as 1/USER_HZ seconds
  * @table: the sysctl table
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 473c162736d69..9226b96f2e89b 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -544,14 +544,16 @@ 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",
 		.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