linux-kernel - [PATCH v3 1/4] module: fix kmemleak annotations for non init ELF sections

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Message-Id: <20230414050836.1984746-2-mcgrof@kernel.org>
Date:   Thu, 13 Apr 2023 22:08:33 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     david@...hat.com, patches@...ts.linux.dev,
        linux-modules@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, pmladek@...e.com,
        petr.pavlu@...e.com, prarit@...hat.com,
        torvalds@...ux-foundation.org, gregkh@...uxfoundation.org,
        rafael@...nel.org
Cc:     christophe.leroy@...roup.eu, tglx@...utronix.de,
        peterz@...radead.org, song@...nel.org, rppt@...nel.org,
        dave@...olabs.net, willy@...radead.org, vbabka@...e.cz,
        mhocko@...e.com, dave.hansen@...ux.intel.com,
        colin.i.king@...il.com, jim.cromie@...il.com,
        catalin.marinas@....com, jbaron@...mai.com,
        rick.p.edgecombe@...el.com, mcgrof@...nel.org
Subject: [PATCH v3 1/4] module: fix kmemleak annotations for non init ELF sections

Commit ac3b43283923 ("module: replace module_layout with module_memory")
reworked the way to handle memory allocations to make it clearer. But it
lost in translation how we handled kmemleak_ignore() or kmemleak_not_leak()
for different ELF sections.

Fix this and clarify the comments a bit more. Contrary to the old way
of using kmemleak_ignore() for init.* ELF sections we stick now only to
kmemleak_not_leak() as per suggestion by Catalin Marinas so to avoid
any false positives and simplify the code.

Fixes: ac3b43283923 ("module: replace module_layout with module_memory")
Reported-by: Jim Cromie <jim.cromie@...il.com>
Acked-by: Song Liu <song@...nel.org>
Suggested-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
---
 kernel/module/main.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/kernel/module/main.c b/kernel/module/main.c
index 5cc21083af04..32554d8a5791 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -2231,13 +2231,18 @@ static int move_module(struct module *mod, struct load_info *info)
 		}
 		mod->mem[type].size = PAGE_ALIGN(mod->mem[type].size);
 		ptr = module_memory_alloc(mod->mem[type].size, type);
-
 		/*
-		 * The pointer to this block is stored in the module structure
-		 * which is inside the block. Just mark it as not being a
-		 * leak.
+                 * The pointer to these blocks of memory are stored on the module
+                 * structure and we keep that around so long as the module is
+                 * around. We only free that memory when we unload the module.
+                 * Just mark them as not being a leak then. The .init* ELF
+                 * sections *do* get freed after boot so we *could* treat them
+                 * slightly differently with kmemleak_ignore() and only grey
+                 * them out as they work as typical memory allocations which
+                 * *do* eventually get freed, but let's just keep things simple
+                 * and avoid *any* false positives.
 		 */
-		kmemleak_ignore(ptr);
+		kmemleak_not_leak(ptr);
 		if (!ptr) {
 			t = type;
 			goto out_enomem;
-- 
2.39.2