From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792774617; b=amRp4i5tiftM94WQnscu1BPTVgqMcJfNU1ZE4oIe88mTdc2b2yGUb5sYfggsmWvVroK4 WPaOUMQWp+1axl1fRfObvixGsGAiziqrK7PS+YEbmqHadYcCtAKR1WdRMAv6iIJlqn28r mf09WzA/XtlCfc9hokCe8o72zeSzz4RHZKiBsqUNYV4Lo9RboxmaYaJDFuj6R5pfDGfiv RP9tIo8nRSqkV9dbB01nNUYwy9gkquwZrUNJ6fY3pLiM93qVcWpAHHq1+460RX7tcybPi 0y9PrqBOLwiOh8x6NpwNGrqItNB2w3h7RZ4P/BHDeNOch7MZ3m/uBahYmlDWzk/4wvQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792774617; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=F6QMhs87baOIkDECRu59eAgPiWgkG6YtzyhVpDxjVKc=; b=SLse++8RFjXl54iEbxuEwTJMLyK7Rioe3lZyEPPI3TMDZg7W6FbTzGMP6Mumgm554ywM wWW273CZjWvYWj223jZ/Oud2GJF3aEAifYaxgDAO5ieOScsbbiVuSbeUfafWyws1RD6C2 kuf4gh4VqMDcql5HcYycJxQXrmbjJEpix86z3ureUm8/H/6qzq+T0brMnD7qYH3H2Xn24 fI9VyG4w7ajs9ZeztC7+umpnCDA0CFBm7HW+HoSwSwAEF72PbNFNOmb+/NkNDY77iJIjK PXapFdwZ7+XiNNAW/1faNKAaYaUQTHny+R8YNvuJFZvYdneyBSpZxdBtKVlcJLuNTRQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=dBji04Hv; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9ACAD606A31D; Fri, 23 Oct 2026 16:56:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=dBji04Hv Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB4C01F01825; Fri, 23 Oct 2026 16:56:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792774617; bh=F6QMhs87baOIkDECRu59eAgPiWgkG6YtzyhVpDxjVKc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dBji04HvWK/FM72xJlq0Tyr/KIKgx8QO16rDxqCUmQblzjEj7Gpw7bl35VifhN2XL ora76zkNAehWFRRbDkXwzizFFCzTvtXKWXh7dp+ElPFj+D/ZAo1raDcUwq8IptdwQP dm+lz86B7Y3yZxc9MwF7y8rbIQ/aWEYrB23xJUq8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Christian Brauner (Amutable)" Subject: [PATCH 7.2 102/242] afs: free the super info after a grace period Date: Fri, 23 Oct 2026 18:39:04 +0200 Message-ID: <20261023163716.193817373@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261023163713.816071858@linuxfoundation.org> References: <20261023163713.816071858@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christian Brauner commit 59e483739f2fd14327ece3f60c4995d060ca46b7 upstream. afs_atcell_get_link() resolves the @cell and .@cell symlinks of a dynamic root in rcu pathwalk mode. Before it looks at the dentry it gets the afs_net through afs_i2net(), which reads ->net_ns from the afs_super_info in sb->s_fs_info. The @cell dentries are kept around when unused and the dynamic root has no ->d_revalidate(), so a lookup that finds @cell in the dcache gets to ->get_link() in rcu mode. afs_kill_super() frees the afs_super_info with a plain kfree() in afs_destroy_sbi(). Right now a pathwalk can't still be in afs_atcell_get_link() at that point, but only by accident. umount(2) waits for a grace period in namespace_unlock() before it drops the mount. And a mount whose last reference goes away elsewhere, like the chdir out of a lazily unmounted directory, still gets a grace period from bdi_unregister(). afs_fill_super() sets up a private bdi, so generic_shutdown_super() unregisters it from kill_anon_super() and bdi_remove_from_list() waits in synchronize_rcu_expedited() before afs_destroy_sbi() runs. That grace period protects the rcu readers of bdi_list in the writeback code. It has nothing to do with pathwalk. Don't rely on it and free the afs_super_info after a grace period. Fixes: 30bca65bbbae ("afs: Make /afs/@cell and /afs/.@cell symlinks") Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20261009-work-fixes-rcu-v1-2-7446d2d335e6@kernel.org Signed-off-by: Christian Brauner (Amutable) Signed-off-by: Greg Kroah-Hartman --- fs/afs/internal.h | 2 ++ fs/afs/super.c | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-) --- a/fs/afs/internal.h +++ b/fs/afs/internal.h @@ -251,6 +251,8 @@ struct afs_super_info { struct afs_volume *volume; /* volume record */ enum afs_flock_mode flock_mode:8; /* File locking emulation mode */ bool dyn_root; /* True if dynamic root */ + /* afs_atcell_get_link() reads ->net_ns in rcu pathwalk */ + struct rcu_head rcu; }; static inline struct afs_super_info *AFS_FS_S(struct super_block *sb) --- a/fs/afs/super.c +++ b/fs/afs/super.c @@ -523,7 +523,7 @@ static void afs_destroy_sbi(struct afs_s afs_put_volume(as->volume, afs_volume_trace_put_destroy_sbi); afs_unuse_cell(as->cell, afs_cell_trace_unuse_sbi); put_net(as->net_ns); - kfree(as); + kfree_rcu(as, rcu); } }