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Message-ID: <20250106.uu8as0Ha6pof@digikod.net>
Date: Mon, 6 Jan 2025 18:04:56 +0100
From: Mickaël Salaün <mic@...ikod.net>
To: Kees Cook <keescook@...omium.org>, linux-hardening@...r.kernel.org
Cc: kernel test robot <lkp@...el.com>, oe-kbuild-all@...ts.linux.dev,
linux-kernel@...r.kernel.org, James Morris <jamorris@...ux.microsoft.com>,
Jann Horn <jannh@...gle.com>
Subject: Re: security/landlock/ruleset.c:96:9: warning: 'memcpy' accessing
4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset
-2147483648
I guess the GCC warning is a false positive?
See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116494
On Sat, Jan 04, 2025 at 07:26:27AM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 0bc21e701a6ffacfdde7f04f87d664d82e8a13bf
> commit: ae271c1b14de343b888e77f74f640e3dcbdeb4c9 landlock: Add ruleset and domain management
> date: 3 years, 8 months ago
> config: csky-randconfig-r026-20230729 (https://download.01.org/0day-ci/archive/20250104/202501040747.S3LYfvYq-lkp@intel.com/config)
> compiler: csky-linux-gcc (GCC) 12.4.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250104/202501040747.S3LYfvYq-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202501040747.S3LYfvYq-lkp@intel.com/
>
> All warnings (new ones prefixed by >>):
>
> security/landlock/ruleset.c: In function 'create_rule':
> >> security/landlock/ruleset.c:96:9: warning: 'memcpy' accessing 4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> 96 | memcpy(new_rule->layers, layers,
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 97 | flex_array_size(new_rule, layers, num_layers));
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> --
> Use of uninitialized value $param in regexp compilation at scripts/kernel-doc line 1532, <IN_FILE> line 146.
> Use of uninitialized value $actual in substitution (s///) at scripts/kernel-doc line 1484, <IN_FILE> line 146.
> Use of uninitialized value $actual in substitution (s///) at scripts/kernel-doc line 1484, <IN_FILE> line 146.
> Use of uninitialized value $param in substitution (s///) at scripts/kernel-doc line 1588, <IN_FILE> line 146.
> Use of uninitialized value $param in pattern match (m//) at scripts/kernel-doc line 1616, <IN_FILE> line 146.
> Use of uninitialized value $param in hash element at scripts/kernel-doc line 1626, <IN_FILE> line 146.
> Use of uninitialized value $param in pattern match (m//) at scripts/kernel-doc line 1626, <IN_FILE> line 146.
> Use of uninitialized value $param in hash element at scripts/kernel-doc line 1627, <IN_FILE> line 146.
> Use of uninitialized value $param in pattern match (m//) at scripts/kernel-doc line 1629, <IN_FILE> line 146.
> Use of uninitialized value $param in concatenation (.) or string at scripts/kernel-doc line 1630, <IN_FILE> line 146.
> >> security/landlock/ruleset.c:146: warning: Function parameter or struct member '' not described in 'insert_rule'
> Use of uninitialized value $param in hash element at scripts/kernel-doc line 1645, <IN_FILE> line 146.
> Use of uninitialized value $parameterlist[2] in join or string at scripts/kernel-doc line 1806, <IN_FILE> line 146.
> >> security/landlock/ruleset.c:146: warning: Excess function parameter 'layers' description in 'insert_rule'
>
>
> vim +/memcpy +96 security/landlock/ruleset.c
>
> 68
> 69 static struct landlock_rule *create_rule(
> 70 struct landlock_object *const object,
> 71 const struct landlock_layer (*const layers)[],
> 72 const u32 num_layers,
> 73 const struct landlock_layer *const new_layer)
> 74 {
> 75 struct landlock_rule *new_rule;
> 76 u32 new_num_layers;
> 77
> 78 build_check_rule();
> 79 if (new_layer) {
> 80 /* Should already be checked by landlock_merge_ruleset(). */
> 81 if (WARN_ON_ONCE(num_layers >= LANDLOCK_MAX_NUM_LAYERS))
> 82 return ERR_PTR(-E2BIG);
> 83 new_num_layers = num_layers + 1;
> 84 } else {
> 85 new_num_layers = num_layers;
> 86 }
> 87 new_rule = kzalloc(struct_size(new_rule, layers, new_num_layers),
> 88 GFP_KERNEL_ACCOUNT);
> 89 if (!new_rule)
> 90 return ERR_PTR(-ENOMEM);
> 91 RB_CLEAR_NODE(&new_rule->node);
> 92 landlock_get_object(object);
> 93 new_rule->object = object;
> 94 new_rule->num_layers = new_num_layers;
> 95 /* Copies the original layer stack. */
> > 96 memcpy(new_rule->layers, layers,
> 97 flex_array_size(new_rule, layers, num_layers));
> 98 if (new_layer)
> 99 /* Adds a copy of @new_layer on the layer stack. */
> 100 new_rule->layers[new_rule->num_layers - 1] = *new_layer;
> 101 return new_rule;
> 102 }
> 103
> 104 static void free_rule(struct landlock_rule *const rule)
> 105 {
> 106 might_sleep();
> 107 if (!rule)
> 108 return;
> 109 landlock_put_object(rule->object);
> 110 kfree(rule);
> 111 }
> 112
> 113 static void build_check_ruleset(void)
> 114 {
> 115 const struct landlock_ruleset ruleset = {
> 116 .num_rules = ~0,
> 117 .num_layers = ~0,
> 118 };
> 119
> 120 BUILD_BUG_ON(ruleset.num_rules < LANDLOCK_MAX_NUM_RULES);
> 121 BUILD_BUG_ON(ruleset.num_layers < LANDLOCK_MAX_NUM_LAYERS);
> 122 }
> 123
> 124 /**
> 125 * insert_rule - Create and insert a rule in a ruleset
> 126 *
> 127 * @ruleset: The ruleset to be updated.
> 128 * @object: The object to build the new rule with. The underlying kernel
> 129 * object must be held by the caller.
> 130 * @layers: One or multiple layers to be copied into the new rule.
> 131 * @num_layers: The number of @layers entries.
> 132 *
> 133 * When user space requests to add a new rule to a ruleset, @layers only
> 134 * contains one entry and this entry is not assigned to any level. In this
> 135 * case, the new rule will extend @ruleset, similarly to a boolean OR between
> 136 * access rights.
> 137 *
> 138 * When merging a ruleset in a domain, or copying a domain, @layers will be
> 139 * added to @ruleset as new constraints, similarly to a boolean AND between
> 140 * access rights.
> 141 */
> 142 static int insert_rule(struct landlock_ruleset *const ruleset,
> 143 struct landlock_object *const object,
> 144 const struct landlock_layer (*const layers)[],
> 145 size_t num_layers)
> > 146 {
> 147 struct rb_node **walker_node;
> 148 struct rb_node *parent_node = NULL;
> 149 struct landlock_rule *new_rule;
> 150
> 151 might_sleep();
> 152 lockdep_assert_held(&ruleset->lock);
> 153 if (WARN_ON_ONCE(!object || !layers))
> 154 return -ENOENT;
> 155 walker_node = &(ruleset->root.rb_node);
> 156 while (*walker_node) {
> 157 struct landlock_rule *const this = rb_entry(*walker_node,
> 158 struct landlock_rule, node);
> 159
> 160 if (this->object != object) {
> 161 parent_node = *walker_node;
> 162 if (this->object < object)
> 163 walker_node = &((*walker_node)->rb_right);
> 164 else
> 165 walker_node = &((*walker_node)->rb_left);
> 166 continue;
> 167 }
> 168
> 169 /* Only a single-level layer should match an existing rule. */
> 170 if (WARN_ON_ONCE(num_layers != 1))
> 171 return -EINVAL;
> 172
> 173 /* If there is a matching rule, updates it. */
> 174 if ((*layers)[0].level == 0) {
> 175 /*
> 176 * Extends access rights when the request comes from
> 177 * landlock_add_rule(2), i.e. @ruleset is not a domain.
> 178 */
> 179 if (WARN_ON_ONCE(this->num_layers != 1))
> 180 return -EINVAL;
> 181 if (WARN_ON_ONCE(this->layers[0].level != 0))
> 182 return -EINVAL;
> 183 this->layers[0].access |= (*layers)[0].access;
> 184 return 0;
> 185 }
> 186
> 187 if (WARN_ON_ONCE(this->layers[0].level == 0))
> 188 return -EINVAL;
> 189
> 190 /*
> 191 * Intersects access rights when it is a merge between a
> 192 * ruleset and a domain.
> 193 */
> 194 new_rule = create_rule(object, &this->layers, this->num_layers,
> 195 &(*layers)[0]);
> 196 if (IS_ERR(new_rule))
> 197 return PTR_ERR(new_rule);
> 198 rb_replace_node(&this->node, &new_rule->node, &ruleset->root);
> 199 free_rule(this);
> 200 return 0;
> 201 }
> 202
> 203 /* There is no match for @object. */
> 204 build_check_ruleset();
> 205 if (ruleset->num_rules >= LANDLOCK_MAX_NUM_RULES)
> 206 return -E2BIG;
> 207 new_rule = create_rule(object, layers, num_layers, NULL);
> 208 if (IS_ERR(new_rule))
> 209 return PTR_ERR(new_rule);
> 210 rb_link_node(&new_rule->node, parent_node, walker_node);
> 211 rb_insert_color(&new_rule->node, &ruleset->root);
> 212 ruleset->num_rules++;
> 213 return 0;
> 214 }
> 215
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
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