Revision 99f62a746066fa436aa15d4606a538569540db08 authored by Vladimir Oltean on 21 September 2020, 22:07:09 UTC, committed by David S. Miller on 22 September 2020, 00:37:44 UTC
When calling the RCU brother of br_vlan_get_pvid(), lockdep warns: ============================= WARNING: suspicious RCU usage 5.9.0-rc3-01631-g13c17acb8e38-dirty #814 Not tainted ----------------------------- net/bridge/br_private.h:1054 suspicious rcu_dereference_protected() usage! Call trace: lockdep_rcu_suspicious+0xd4/0xf8 __br_vlan_get_pvid+0xc0/0x100 br_vlan_get_pvid_rcu+0x78/0x108 The warning is because br_vlan_get_pvid_rcu() calls nbp_vlan_group() which calls rtnl_dereference() instead of rcu_dereference(). In turn, rtnl_dereference() calls rcu_dereference_protected() which assumes operation under an RCU write-side critical section, which obviously is not the case here. So, when the incorrect primitive is used to access the RCU-protected VLAN group pointer, READ_ONCE() is not used, which may cause various unexpected problems. I'm sad to say that br_vlan_get_pvid() and br_vlan_get_pvid_rcu() cannot share the same implementation. So fix the bug by splitting the 2 functions, and making br_vlan_get_pvid_rcu() retrieve the VLAN groups under proper locking annotations. Fixes: 7582f5b70f9a ("bridge: add br_vlan_get_pvid_rcu()") Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1 parent 47cec3f
test_bitops.c
// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2020 Intel Corporation
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/init.h>
#include <linux/module.h>
#include <linux/printk.h>
/* a tiny module only meant to test
*
* set/clear_bit
* get_count_order/long
*/
/* use an enum because thats the most common BITMAP usage */
enum bitops_fun {
BITOPS_4 = 4,
BITOPS_7 = 7,
BITOPS_11 = 11,
BITOPS_31 = 31,
BITOPS_88 = 88,
BITOPS_LAST = 255,
BITOPS_LENGTH = 256
};
static DECLARE_BITMAP(g_bitmap, BITOPS_LENGTH);
static unsigned int order_comb[][2] = {
{0x00000003, 2},
{0x00000004, 2},
{0x00001fff, 13},
{0x00002000, 13},
{0x50000000, 31},
{0x80000000, 31},
{0x80003000, 32},
};
#ifdef CONFIG_64BIT
static unsigned long order_comb_long[][2] = {
{0x0000000300000000, 34},
{0x0000000400000000, 34},
{0x00001fff00000000, 45},
{0x0000200000000000, 45},
{0x5000000000000000, 63},
{0x8000000000000000, 63},
{0x8000300000000000, 64},
};
#endif
static int __init test_bitops_startup(void)
{
int i, bit_set;
pr_info("Starting bitops test\n");
set_bit(BITOPS_4, g_bitmap);
set_bit(BITOPS_7, g_bitmap);
set_bit(BITOPS_11, g_bitmap);
set_bit(BITOPS_31, g_bitmap);
set_bit(BITOPS_88, g_bitmap);
for (i = 0; i < ARRAY_SIZE(order_comb); i++) {
if (order_comb[i][1] != get_count_order(order_comb[i][0]))
pr_warn("get_count_order wrong for %x\n",
order_comb[i][0]);
}
for (i = 0; i < ARRAY_SIZE(order_comb); i++) {
if (order_comb[i][1] != get_count_order_long(order_comb[i][0]))
pr_warn("get_count_order_long wrong for %x\n",
order_comb[i][0]);
}
#ifdef CONFIG_64BIT
for (i = 0; i < ARRAY_SIZE(order_comb_long); i++) {
if (order_comb_long[i][1] !=
get_count_order_long(order_comb_long[i][0]))
pr_warn("get_count_order_long wrong for %lx\n",
order_comb_long[i][0]);
}
#endif
barrier();
clear_bit(BITOPS_4, g_bitmap);
clear_bit(BITOPS_7, g_bitmap);
clear_bit(BITOPS_11, g_bitmap);
clear_bit(BITOPS_31, g_bitmap);
clear_bit(BITOPS_88, g_bitmap);
bit_set = find_first_bit(g_bitmap, BITOPS_LAST);
if (bit_set != BITOPS_LAST)
pr_err("ERROR: FOUND SET BIT %d\n", bit_set);
pr_info("Completed bitops test\n");
return 0;
}
static void __exit test_bitops_unstartup(void)
{
}
module_init(test_bitops_startup);
module_exit(test_bitops_unstartup);
MODULE_AUTHOR("Jesse Brandeburg <jesse.brandeburg@intel.com>, Wei Yang <richard.weiyang@gmail.com>");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Bit testing module");
![swh spinner](/static/img/swh-spinner.gif)
Computing file changes ...