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Received: from authenticated-user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) (envelope-from ) id 1xHiuh-0061vO-2m; Fri, 16 Oct 2026 14:28:04 +0000 From: Breno Leitao Date: Fri, 16 Oct 2026 07:27:58 -0700 Subject: [PATCH] init: do_mounts: free the ramfs info of the boot rootfs Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261016-rootfs-kill-sb-v1-1-7631af3ba35f@debian.org> X-B4-Tracking: v=1; b=H4sIAG400moC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzNDA0Mz3aL8/JK0Yt3szJwc3eIkXZM0wyRTS/OUxCQjEyWgpoKi1LTMCrC B0bEQfnFpUlZqcgnIFKXaWgBCawqQcgAAAA== X-Change-ID: 20261016-rootfs-kill-sb-4f1b597dab24 To: Alexander Viro , Christian Brauner , Jan Kara , Shuah Khan Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, linux-kselftest@vger.kernel.org, kernel-team@meta.com, Breno Leitao X-Mailer: b4 0.15-dev-47773 X-Developer-Signature: v=1; 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a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Debian-User: leitao Kmemleak is reporting the following leak in ramfs_init_fs_context: unreferenced object 0xffff000080302480 (size 8): comm "swapper/0", pid 0, jiffies 4294667306 hex dump (first 8 bytes): ed 01 00 00 00 00 00 00 ........ backtrace (crc bea23b04): __kmalloc_cache_noprof+0x28c/0x5a0 ramfs_init_fs_context+0x5c/0xf8 rootfs_init_fs_context+0x30/0x40 alloc_fs_context+0x4c0/0x6a8 fs_context_for_mount+0x28/0x40 vfs_kern_mount+0x40/0x220 init_mount_tree+0x80/0x440 mnt_init+0x138/0x170 vfs_caches_init+0x2c/0x48 start_kernel+0x350/0x3f8 When init pivot_root()s away from a ramfs-backed boot rootfs and unmounts it, the rootfs superblock is killed with kill_anon_super() and the struct ramfs_fs_info allocated by ramfs_init_fs_context() is never freed. Kill a ramfs-backed rootfs with ramfs_kill_sb(). A tmpfs-backed one keeps kill_anon_super(), as shmem frees its info in ->put_super. Fixes: 576ee5dfd459 ("fs: add immutable rootfs") Signed-off-by: Breno Leitao --- init/do_mounts.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/init/do_mounts.c b/init/do_mounts.c index 95e0b3a0f711bd..b088021b1546d8 100644 --- a/init/do_mounts.c +++ b/init/do_mounts.c @@ -503,10 +503,18 @@ static int rootfs_init_fs_context(struct fs_context *fc) return ramfs_init_fs_context(fc); } +static void rootfs_kill_sb(struct super_block *sb) +{ + if (IS_ENABLED(CONFIG_TMPFS) && is_tmpfs) + kill_anon_super(sb); + else + ramfs_kill_sb(sb); +} + struct file_system_type rootfs_fs_type = { .name = "rootfs", .init_fs_context = rootfs_init_fs_context, - .kill_sb = kill_anon_super, + .kill_sb = rootfs_kill_sb, }; void __init init_rootfs(void) --- base-commit: d419d682257d813f6cb7a28e42b35d0edf4ad038 change-id: 20261016-rootfs-kill-sb-4f1b597dab24 Best regards, -- Breno Leitao