From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A470F43A7FC; Mon, 17 Aug 2026 13:31:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786973479; cv=none; b=AIzK5yuI6NgfmDN4MQpLSpD89OUES+/JeFGb1j0cHcwVPXut8RLPkuhdy5wJ4EfZ46wNl9gBSEAJslwrv8+66YxnmJtU1iyKkwtzPKEpUHQ1+lUx10NBE/+u1MWS5PbihT212UeCenrcVL9hvPEMY0sT69Ws9X5f49az5vssblc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786973479; c=relaxed/simple; bh=ED5Qg0LYVn7hEZ/2Si8nDrmTYjtnEaK2CGulku8nQxI=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Ebx4y41z2Ec4NLBnyy19ajNFLWZmMP0XffyucYowfa5A78+8QjxyJGkw+iwiqWDeM/aDHuWWwOfRqrGV7DHCtBKrBxBByQiWqCBbjsoZrrN7kwmCfU8MCBt69iMEKhfEfQw+KJmRO10x5pDZt7YCJ4BrgzGT3+rrLQywVzp897o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WdFhCiYI; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WdFhCiYI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6CC031F000E9; Mon, 17 Aug 2026 13:31:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786973474; bh=cIxHbbJeI7a+/HWpA4JHUC1g6JD670pmSICI8yfcke0=; h=Subject:From:To:Cc:Date:In-Reply-To:References; b=WdFhCiYI2ZwXtlbSQ9o25m8hLjiTvc8lmbyo64uw0vpiSmLPcihjJkYhIf5vqBUU1 /qazx40EWMse4Mbgp7elOf6rWBrsavW10cTD0MK8iWddqgKk2iiFs0Ar5YwaExhP4o LJZjFNTki0GB698Ism32PelmgnmZilHYoVoLcFSaVuJtWMt2IyMEInY8tUy2KJNK0h jrYZB2SM3jBF/bdf9y3bozTIZNi8HFNkeHr4q4gx3k/+8n9fVAgCDYekNtwnEMhlng 03mzuI1Z07yk16SK8Ojmhvzk8jlzIeUCLnrL5Bm5AtAJeMpMMvWBwRBh7Fi97E08cq SWVCOhLZ3gHyw== Message-ID: <4a3a7a0cd52e8fc571c967716756f49b8a0f95f2.camel@kernel.org> Subject: Re: [PATCH] SUNRPC: update clnt->pipefs_sb on pipefs MOUNT/UMOUNT events From: Jeff Layton To: Shigeru Yoshida , Trond Myklebust , Anna Schumaker , Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , felix Cc: linux-nfs@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 17 Aug 2026 09:31:12 -0400 In-Reply-To: <20260817080013.564939-1-syoshida@redhat.com> References: <20260817080013.564939-1-syoshida@redhat.com> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ cDEsvv5IMmeMe1/qLZ6NaVkNuL3WOXvxaVT9USW1+/SGipO2IpKJjeDZfehlB/kpfF24+RrK+seQf 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Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-08-17 at 17:00 +0900, Shigeru Yoshida wrote: > Commit bfca5fb4e97c ("SUNRPC: Fix RPC client cleaned up the freed > pipefs dentries") added a clnt->pipefs_sb field and a consistency > check in rpc_clnt_remove_pipedir() so that pipedir cleanup is skipped > when the current superblock does not match the one recorded in the > client. >=20 > However, __rpc_clnt_handle_event() never updates clnt->pipefs_sb when > it creates or removes pipedirs in response to RPC_PIPEFS_MOUNT and > RPC_PIPEFS_UMOUNT notifications. >=20 > This causes a problem for RPC clients that are registered before > rpc_pipefs is mounted (e.g., before rpc_pipefs is mounted during boot, > or after it has been unmounted). Such clients have clnt->pipefs_sb set > to NULL at registration time because rpc_get_sb_net() returns NULL. > When rpc_pipefs is mounted later, __rpc_clnt_handle_event(MOUNT) > creates the pipedir but leaves clnt->pipefs_sb as NULL. When the > client is later destroyed, rpc_clnt_remove_pipedir() sees that the > current superblock does not match clnt->pipefs_sb and skips cleanup, > leaving orphaned dentries whose RPC_I(inode)->private pointers > reference freed rpc_clnt memory. Any subsequent access to these > orphaned info files triggers a use-after-free [1]. >=20 > Fix this by setting clnt->pipefs_sb in __rpc_clnt_handle_event() on > MOUNT and clearing it on UMOUNT, mirroring what rpc_setup_pipedir() > already does at client registration time. >=20 > [1] > BUG: KASAN: slab-use-after-free in rpc_info_open (net/sunrpc/rpc_pipe.c:4= 26) > Read of size 4 at addr ffff88802ebe0800 by task cat/5079 >=20 > Call Trace: > > ... > rpc_info_open (net/sunrpc/rpc_pipe.c:426) > do_dentry_open (fs/open.c:947) > vfs_open (fs/open.c:1052) > path_openat (fs/namei.c:4700 fs/namei.c:4863) > do_file_open (fs/namei.c:4892) > do_sys_openat2 (fs/open.c:1368) > __x64_sys_openat (fs/open.c:1385) > do_syscall_64 (arch/x86/entry/syscall_64.c:94) > entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) > >=20 > Allocated by task 5048: > ... > rpc_new_client (net/sunrpc/clnt.c:377) > __rpc_clone_client (net/sunrpc/clnt.c:645) > rpc_clone_client_set_auth (net/sunrpc/clnt.c:706) > nfs_init_server_rpcclient (fs/nfs/client.c:640) > nfs_clone_server (fs/nfs/client.c:1247) > nfs4_clone_server (fs/nfs/nfs4proc.c:10683) > nfs_do_submount (fs/nfs/namespace.c:288) > ... >=20 > Freed by task 24: > ... > kfree (mm/slub.c:6692) > rpc_free_client_work (net/sunrpc/clnt.c:987) > process_scheduled_works (kernel/workqueue.c:3405) > worker_thread (kernel/workqueue.c:3486) > ... >=20 > Fixes: bfca5fb4e97c ("SUNRPC: Fix RPC client cleaned up the freed pipefs = dentries") > Assisted-by: Claude:claude-opus-4-6 > Signed-off-by: Shigeru Yoshida > --- > net/sunrpc/clnt.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) >=20 > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c > index efa26899bc7d..55617d263d2f 100644 > --- a/net/sunrpc/clnt.c > +++ b/net/sunrpc/clnt.c > @@ -179,11 +179,17 @@ static int rpc_clnt_skip_event(struct rpc_clnt *cln= t, unsigned long event) > static int __rpc_clnt_handle_event(struct rpc_clnt *clnt, unsigned long = event, > struct super_block *sb) > { > + int err; > + > switch (event) { > case RPC_PIPEFS_MOUNT: > - return rpc_setup_pipedir_sb(sb, clnt); > + err =3D rpc_setup_pipedir_sb(sb, clnt); > + if (!err) > + clnt->pipefs_sb =3D sb; > + return err; > case RPC_PIPEFS_UMOUNT: > __rpc_clnt_remove_pipedir(clnt); > + clnt->pipefs_sb =3D NULL; > break; > default: > printk(KERN_ERR "%s: unknown event: %ld\n", __func__, event); Looks right. Reviewed-by: Jeff Layton