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The kernel has only two users of proc_do_large_bitmap(), the kernel CPU watchdog, and the ip_local_reserved_ports. Refer to watchdog_cpumask and ip_local_reserved_ports in Documentation for further details on these. When you input a large buffer into these, when it is larger than PAGE_SIZE- 1, the input data gets misparsed, and the user get incorrectly informed that the desired input value was set. This commit implements a test which mimics and exploits that use case, it uses a bitmap size, as in the watchdog case. The bitmap is used to test the bitmap proc handler, proc_do_large_bitmap(). The next commit fixes this issue. [akpm@linux-foundation.org: move proc_do_large_bitmap() export to EOF] [mcgrof@kernel.org: use new target description for backward compatibility] [mcgrof@kernel.org: augment test number to 50, ran into issues with bash string comparisons when testing up to 50 cases.] [mcgrof@kernel.org: introduce and use verify_diff_proc_file() to use diff] [mcgrof@kernel.org: use mktemp for tmp file] [mcgrof@kernel.org: merge shell test and C code] [mcgrof@kernel.org: commit log love] [mcgrof@kernel.org: export proc_do_large_bitmap() to allow for the test [mcgrof@kernel.org: check for the return value when writing to the proc file] Link: http://lkml.kernel.org/r/20190320222831.8243-6-mcgrof@kernel.org Signed-off-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> Acked-by: Kees Cook <keescook@chromium.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
165 lines
3.7 KiB
C
165 lines
3.7 KiB
C
/*
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* proc sysctl test driver
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*
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* Copyright (C) 2017 Luis R. Rodriguez <mcgrof@kernel.org>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or at your option any
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* later version; or, when distributed separately from the Linux kernel or
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* when incorporated into other software packages, subject to the following
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* license:
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of copyleft-next (version 0.3.1 or later) as published
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* at http://copyleft-next.org/.
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*/
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/*
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* This module provides an interface to the the proc sysctl interfaces. This
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* driver requires CONFIG_PROC_SYSCTL. It will not normally be loaded by the
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* system unless explicitly requested by name. You can also build this driver
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* into your kernel.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/init.h>
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#include <linux/list.h>
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#include <linux/module.h>
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#include <linux/printk.h>
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#include <linux/fs.h>
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#include <linux/miscdevice.h>
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#include <linux/slab.h>
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#include <linux/uaccess.h>
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#include <linux/async.h>
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#include <linux/delay.h>
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#include <linux/vmalloc.h>
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static int i_zero;
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static int i_one_hundred = 100;
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struct test_sysctl_data {
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int int_0001;
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int int_0002;
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int int_0003[4];
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unsigned int uint_0001;
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char string_0001[65];
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#define SYSCTL_TEST_BITMAP_SIZE 65536
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unsigned long *bitmap_0001;
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};
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static struct test_sysctl_data test_data = {
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.int_0001 = 60,
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.int_0002 = 1,
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.int_0003[0] = 0,
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.int_0003[1] = 1,
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.int_0003[2] = 2,
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.int_0003[3] = 3,
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.uint_0001 = 314,
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.string_0001 = "(none)",
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};
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/* These are all under /proc/sys/debug/test_sysctl/ */
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static struct ctl_table test_table[] = {
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{
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.procname = "int_0001",
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.data = &test_data.int_0001,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_minmax,
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.extra1 = &i_zero,
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.extra2 = &i_one_hundred,
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},
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{
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.procname = "int_0002",
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.data = &test_data.int_0002,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "int_0003",
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.data = &test_data.int_0003,
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.maxlen = sizeof(test_data.int_0003),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "uint_0001",
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.data = &test_data.uint_0001,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_douintvec,
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},
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{
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.procname = "string_0001",
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.data = &test_data.string_0001,
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.maxlen = sizeof(test_data.string_0001),
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.mode = 0644,
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.proc_handler = proc_dostring,
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},
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{
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.procname = "bitmap_0001",
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.data = &test_data.bitmap_0001,
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.maxlen = SYSCTL_TEST_BITMAP_SIZE,
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.mode = 0644,
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.proc_handler = proc_do_large_bitmap,
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},
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{ }
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};
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static struct ctl_table test_sysctl_table[] = {
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{
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.procname = "test_sysctl",
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.maxlen = 0,
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.mode = 0555,
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.child = test_table,
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},
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{ }
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};
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static struct ctl_table test_sysctl_root_table[] = {
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{
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.procname = "debug",
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.maxlen = 0,
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.mode = 0555,
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.child = test_sysctl_table,
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},
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{ }
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};
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static struct ctl_table_header *test_sysctl_header;
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static int __init test_sysctl_init(void)
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{
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test_data.bitmap_0001 = kzalloc(SYSCTL_TEST_BITMAP_SIZE/8, GFP_KERNEL);
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if (!test_data.bitmap_0001)
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return -ENOMEM;
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test_sysctl_header = register_sysctl_table(test_sysctl_root_table);
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if (!test_sysctl_header) {
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kfree(test_data.bitmap_0001);
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return -ENOMEM;
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}
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return 0;
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}
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late_initcall(test_sysctl_init);
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static void __exit test_sysctl_exit(void)
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{
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kfree(test_data.bitmap_0001);
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if (test_sysctl_header)
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unregister_sysctl_table(test_sysctl_header);
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}
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module_exit(test_sysctl_exit);
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MODULE_AUTHOR("Luis R. Rodriguez <mcgrof@kernel.org>");
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MODULE_LICENSE("GPL");
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