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5e6ded2e7a
Clang static analysis reports this issue
livepatch-shadow-fix1.c:113:2: warning: Use of
memory after it is freed
pr_info("%s: dummy @ %p, prevented leak @ %p\n",
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The pointer is freed in the previous statement.
Reorder the pr_info to report before the free.
Similar issue in livepatch-shadow-fix2.c
Note that it is a false positive. pr_info() just prints the address.
The freed memory is not accessed. Well, the static analyzer could not
know this easily.
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: David Vernet <void@manifault.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
[pmladek@suse.com: Note about that it was false positive.]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220320015143.2208591-1-trix@redhat.com
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 <joe.lawrence@redhat.com>
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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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pr_info("%s: dummy @ %p, prevented leak @ %p\n",
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__func__, d, *shadow_leak);
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kfree(*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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