linux-kernel - [PATCH] fs: hide dentry_cache behind runtime const machinery

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20251105153622.758836-1-mjguzik@gmail.com>
Date: Wed,  5 Nov 2025 16:36:22 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: brauner@...nel.org
Cc: viro@...iv.linux.org.uk,
	jack@...e.cz,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	Mateusz Guzik <mjguzik@...il.com>
Subject: [PATCH] fs: hide dentry_cache behind runtime const machinery

Signed-off-by: Mateusz Guzik <mjguzik@...il.com>
---
 fs/dcache.c                       | 6 ++++--
 include/asm-generic/vmlinux.lds.h | 3 ++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index de3e4e9777ea..531835e8637c 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -86,7 +86,8 @@ __cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
 
 EXPORT_SYMBOL(rename_lock);
 
-static struct kmem_cache *dentry_cache __ro_after_init;
+static struct kmem_cache *__dentry_cache __ro_after_init;
+#define dentry_cache runtime_const_ptr(__dentry_cache)
 
 const struct qstr empty_name = QSTR_INIT("", 0);
 EXPORT_SYMBOL(empty_name);
@@ -3216,9 +3217,10 @@ static void __init dcache_init(void)
 	 * but it is probably not worth it because of the cache nature
 	 * of the dcache.
 	 */
-	dentry_cache = KMEM_CACHE_USERCOPY(dentry,
+	__dentry_cache = KMEM_CACHE_USERCOPY(dentry,
 		SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_ACCOUNT,
 		d_shortname.string);
+	runtime_const_init(ptr, __dentry_cache);
 
 	/* Hash may have been set up in dcache_init_early */
 	if (!hashdist)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index e04d56a5332e..caef183a73bc 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -955,7 +955,8 @@ defined(CONFIG_AUTOFDO_CLANG) || defined(CONFIG_PROPELLER_CLANG)
 
 #define RUNTIME_CONST_VARIABLES						\
 		RUNTIME_CONST(shift, d_hash_shift)			\
-		RUNTIME_CONST(ptr, dentry_hashtable)
+		RUNTIME_CONST(ptr, dentry_hashtable)			\
+		RUNTIME_CONST(ptr, __dentry_cache)
 
 /* Alignment must be consistent with (kunit_suite *) in include/kunit/test.h */
 #define KUNIT_TABLE()							\
-- 
2.48.1