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Revision 7ff57e98fb78ad94edafbdc7435f2d745e9e6bb5 authored by Fabio M. De Francesco on 23 February 2022, 10:02:52 UTC, committed by Jakub Kicinski on 24 February 2022, 17:09:33 UTC 
net/smc: Use a mutex for locking "struct smc_pnettable"
 
smc_pnetid_by_table_ib() uses read_lock() and then it calls smc_pnet_apply_ib()
which, in turn, calls mutex_lock(&smc_ib_devices.mutex).

read_lock() disables preemption. Therefore, the code acquires a mutex while in
atomic context and it leads to a SAC bug.

Fix this bug by replacing the rwlock with a mutex.

Reported-and-tested-by: syzbot+4f322a6d84e991c38775@syzkaller.appspotmail.com
Fixes: 64e28b52c7a6 ("net/smc: add pnet table namespace support")
Confirmed-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Acked-by: Karsten Graul <kgraul@linux.ibm.com>
Link: https://lore.kernel.org/r/20220223100252.22562-1-fmdefrancesco@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Raw File
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 that's 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");
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