[PATCH 1/1] alloc_tag: fix empty codetag module section handling

[Suren Baghdasaryan <surenb@google.com>]

When a module does not have any allocations, it's allocation tag section
is empty and codetag_alloc_module_section() returns NULL. However this
condition should never happen because codetag_needs_module_section() will
detect an empty section and avoid calling codetag_alloc_module_section().
Change codetag_alloc_module_section() to never return NULL, which should
prevent static checker warnings. Add a WARN_ON() and a proper error
reporting in case codetag_alloc_module_section() returns NULL, to prevent
future codetag type implementations from returning NULL from their
cttype->desc.alloc_section_mem() operation.

Fixes: 61c9e58f3a10 ("alloc_tag: load module tags into separate contiguous memory")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/50f12fa1-17c1-4940-a6bf-beaf61f6b17a@stanley.mountain/
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 kernel/module/main.c | 4 ++++
 lib/alloc_tag.c      | 2 +-
 lib/codetag.c        | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 129c98e6380d..00c16f5c5568 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2316,6 +2316,10 @@ static int move_module(struct module *mod, struct load_info *info)
 		if (codetag_needs_module_section(mod, sname, shdr->sh_size)) {
 			dest = codetag_alloc_module_section(mod, sname, shdr->sh_size,
 					arch_mod_section_prepend(mod, i), shdr->sh_addralign);
+			if (WARN_ON(!dest)) {
+				ret = -EINVAL;
+				goto out_err;
+			}
 			if (IS_ERR(dest)) {
 				ret = PTR_ERR(dest);
 				goto out_err;
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 1c74942e6dfd..00ab18ea452a 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -437,7 +437,7 @@ static void *reserve_module_tags(struct module *mod, unsigned long size,
 
 	/* If no tags return NULL */
 	if (size < sizeof(struct alloc_tag))
-		return NULL;
+		return ERR_PTR(-EINVAL);
 
 	/*
 	 * align is always power of 2, so we can use IS_ALIGNED and ALIGN.
diff --git a/lib/codetag.c b/lib/codetag.c
index 4949511b4933..42aadd6c1454 100644
--- a/lib/codetag.c
+++ b/lib/codetag.c
@@ -244,7 +244,7 @@ void *codetag_alloc_module_section(struct module *mod, const char *name,
 {
 	const char *type_name = name + strlen(CODETAG_SECTION_PREFIX);
 	struct codetag_type *cttype;
-	void *ret = NULL;
+	void *ret = ERR_PTR(-EINVAL);
 
 	mutex_lock(&codetag_lock);
 	list_for_each_entry(cttype, &codetag_types, link) {

base-commit: 758db9ca0107bc6c00f0ed4808974d66c8dc2fea
-- 
2.47.0.163.g1226f6d8fa-goog