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>
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crc64.c
// SPDX-License-Identifier: GPL-2.0
/*
* Normal 64-bit CRC calculation.
*
* This is a basic crc64 implementation following ECMA-182 specification,
* which can be found from,
* https://www.ecma-international.org/publications/standards/Ecma-182.htm
*
* Dr. Ross N. Williams has a great document to introduce the idea of CRC
* algorithm, here the CRC64 code is also inspired by the table-driven
* algorithm and detail example from this paper. This paper can be found
* from,
* http://www.ross.net/crc/download/crc_v3.txt
*
* crc64table[256] is the lookup table of a table-driven 64-bit CRC
* calculation, which is generated by gen_crc64table.c in kernel build
* time. The polynomial of crc64 arithmetic is from ECMA-182 specification
* as well, which is defined as,
*
* x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
* x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
* x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
* x^7 + x^4 + x + 1
*
* Copyright 2018 SUSE Linux.
* Author: Coly Li <colyli@suse.de>
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/crc64.h>
#include "crc64table.h"
MODULE_DESCRIPTION("CRC64 calculations");
MODULE_LICENSE("GPL v2");
/**
* crc64_be - Calculate bitwise big-endian ECMA-182 CRC64
* @crc: seed value for computation. 0 or (u64)~0 for a new CRC calculation,
or the previous crc64 value if computing incrementally.
* @p: pointer to buffer over which CRC64 is run
* @len: length of buffer @p
*/
u64 __pure crc64_be(u64 crc, const void *p, size_t len)
{
size_t i, t;
const unsigned char *_p = p;
for (i = 0; i < len; i++) {
t = ((crc >> 56) ^ (*_p++)) & 0xFF;
crc = crc64table[t] ^ (crc << 8);
}
return crc;
}
EXPORT_SYMBOL_GPL(crc64_be);
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