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Petr Mladek
8f6b88662c
The "leak" pointer, in the sample of shadow variable API, is allocated as sizeof(int). Let's help developers and static analyzers with understanding the code by using the appropriate pointer type. Reported-by: Dan Carpenter <[email protected]> Signed-off-by: Petr Mladek <[email protected]> Reviewed-by: Joe Lawrence <[email protected]> Acked-by: Miroslav Benes <[email protected]> Reviewed-by: Kamalesh Babulal <[email protected]> Signed-off-by: Jiri Kosina <[email protected]>
133 lines
2.9 KiB
C
133 lines
2.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2017 Joe Lawrence <[email protected]>
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*/
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/*
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* livepatch-shadow-fix2.c - Shadow variables, livepatch demo
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*
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* Purpose
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* -------
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*
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* Adds functionality to livepatch-shadow-mod's in-flight data
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* structures through a shadow variable. The livepatch patches a
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* routine that periodically inspects data structures, incrementing a
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* per-data-structure counter, creating the counter if needed.
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*
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*
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* Usage
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* -----
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*
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* This module is not intended to be standalone. See the "Usage"
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* section of livepatch-shadow-mod.c.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/livepatch.h>
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#include <linux/slab.h>
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/* Shadow variable enums */
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#define SV_LEAK 1
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#define SV_COUNTER 2
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struct dummy {
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struct list_head list;
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unsigned long jiffies_expire;
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};
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static bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies)
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{
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int *shadow_count;
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/*
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* Patch: handle in-flight dummy structures, if they do not
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* already have a SV_COUNTER shadow variable, then attach a
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* new one.
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*/
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shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER,
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sizeof(*shadow_count), GFP_NOWAIT,
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NULL, NULL);
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if (shadow_count)
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*shadow_count += 1;
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return time_after(jiffies, d->jiffies_expire);
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}
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static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data)
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{
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void *d = obj;
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int **shadow_leak = shadow_data;
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kfree(*shadow_leak);
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pr_info("%s: dummy @ %p, prevented leak @ %p\n",
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__func__, d, *shadow_leak);
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}
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static void livepatch_fix2_dummy_free(struct dummy *d)
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{
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int **shadow_leak;
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int *shadow_count;
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/* Patch: copy the memory leak patch from the fix1 module. */
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shadow_leak = klp_shadow_get(d, SV_LEAK);
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if (shadow_leak)
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klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor);
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else
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pr_info("%s: dummy @ %p leaked!\n", __func__, d);
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/*
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* Patch: fetch the SV_COUNTER shadow variable and display
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* the final count. Detach the shadow variable.
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*/
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shadow_count = klp_shadow_get(d, SV_COUNTER);
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if (shadow_count) {
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pr_info("%s: dummy @ %p, check counter = %d\n",
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__func__, d, *shadow_count);
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klp_shadow_free(d, SV_COUNTER, NULL);
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}
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kfree(d);
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}
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static struct klp_func funcs[] = {
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{
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.old_name = "dummy_check",
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.new_func = livepatch_fix2_dummy_check,
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},
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{
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.old_name = "dummy_free",
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.new_func = livepatch_fix2_dummy_free,
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}, { }
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};
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static struct klp_object objs[] = {
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{
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.name = "livepatch_shadow_mod",
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.funcs = funcs,
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}, { }
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};
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static struct klp_patch patch = {
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.mod = THIS_MODULE,
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.objs = objs,
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};
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static int livepatch_shadow_fix2_init(void)
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{
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return klp_enable_patch(&patch);
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}
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static void livepatch_shadow_fix2_exit(void)
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{
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/* Cleanup any existing SV_COUNTER shadow variables */
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klp_shadow_free_all(SV_COUNTER, NULL);
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}
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module_init(livepatch_shadow_fix2_init);
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module_exit(livepatch_shadow_fix2_exit);
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MODULE_LICENSE("GPL");
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MODULE_INFO(livepatch, "Y");
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