From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 EB100216A14; Fri, 11 Oct 2024 13:04:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728651895; cv=none; b=jCBIt3vQhFymTiare41ZOQYTzyVwtclCCZZDnup+yBR1E5s7DDZKPmDSbPjXEX+F+M8vJVdI+idp+c+ieyL3d3gEKVwG3zP4+tVWE0RnTBTcTZyfutmYjyALkcD3peONzlrEDUPPzGRaASkCxQN4KMQ19RalBnxGgnvKQFzAFFo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728651895; c=relaxed/simple; bh=NxAglJjLgkj0eQvaRxN5LlRLkWEy5OEDwnaSVtlUGtg=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=GDo6YlVZg9OhPdahNnoDcZ0Pn8DbbbHCRKcrfq40XwnzGY9mOoQ7yidsmMlMb837zsmsoubP2KMTbycjnWU/W7GU7ODP0iXZf/AObnjt5HiAMDqrua3CWXNKa6T7t2TSoz+M8KNOZobXaWRlTrbxhLkt8bmmqD7/JkEaByf6aQ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=U8crctls; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="U8crctls" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F557C4CEC3; Fri, 11 Oct 2024 13:04:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728651894; bh=NxAglJjLgkj0eQvaRxN5LlRLkWEy5OEDwnaSVtlUGtg=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=U8crctlslPlrC6U5KDZV+kaeJf/CQ5dW2Zv2oizRsacjvEDG67zLWX+V/WWTMZhAH DiPCCvbfLlEWMUa7iU+1ek9fs52eJAU6tIB/AP+nJ2CXJMfnIAVFvpsFELXhcgYz1c yVHQAqh+/ankvAB8FtFvcVSGcWDnIPdPwbcWkY6+1BymS8tV79qlLgebYD5Rq0eGs3 JeHvrUJxIeerhN2BIVXlwRggALvK+zP8CGKZEW6IEC/O9of/embYBMrdSQLKbWr9l3 /EsJiVfAdd4Vtkyqk92lU1sKZvvNnSTSwwT2NFfJ4e/qaefmtMIYSZj2zfEDufwIjU 3YAEmAVXtmUew== Message-ID: Subject: Re: [PATCH 1/1] nfsd: fix race between laundromat and free_stateid From: Jeff Layton To: Olga Kornievskaia , chuck.lever@oracle.com Cc: linux-nfs@vger.kernel.org, stable@vger.kernel.org Date: Fri, 11 Oct 2024 09:04:53 -0400 In-Reply-To: <20241010221801.35462-1-okorniev@redhat.com> References: <20241010221801.35462-1-okorniev@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 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operation. Laundromat thread > finds that delegation has expired and needs to be revoked so it > marks the delegation stid revoked and it puts it on a reaper list > but then it unlock the state lock and the actual delegation revocation > happens without the lock. Once the stid is marked revoked a racing > free_stateid processing thread does the following (1) it calls > list_del_init() which removes it from the reaper list and (2) frees > the delegation stid structure. The laundromat thread ends up not > calling the revoke_delegation() function for this particular delegation > but that means it will no release the lock lease that exists on > the file. >=20 > Now, a new open for this file comes in and ends up finding that > lease list isn't empty and calls nfsd_breaker_owns_lease() which ends > up trying to derefence a freed delegation stateid. Leading to the > followint use-after-free KASAN warning: >=20 > kernel: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > kernel: BUG: KASAN: slab-use-after-free in nfsd_breaker_owns_lease+0x140/= 0x160 [nfsd] > kernel: Read of size 8 at addr ffff0000e73cd0c8 by task nfsd/6205 > kernel: > kernel: CPU: 2 UID: 0 PID: 6205 Comm: nfsd Kdump: loaded Not tainted 6.11= .0-rc7+ #9 > kernel: Hardware name: Apple Inc. Apple Virtualization Generic Platform, = BIOS 2069.0.0.0.0 08/03/2024 > kernel: Call trace: > kernel: dump_backtrace+0x98/0x120 > kernel: show_stack+0x1c/0x30 > kernel: dump_stack_lvl+0x80/0xe8 > kernel: print_address_description.constprop.0+0x84/0x390 > kernel: print_report+0xa4/0x268 > kernel: kasan_report+0xb4/0xf8 > kernel: __asan_report_load8_noabort+0x1c/0x28 > kernel: nfsd_breaker_owns_lease+0x140/0x160 [nfsd] > kernel: leases_conflict+0x68/0x370 > kernel: __break_lease+0x204/0xc38 > kernel: nfsd_open_break_lease+0x8c/0xf0 [nfsd] > kernel: nfsd_file_do_acquire+0xb3c/0x11d0 [nfsd] > kernel: nfsd_file_acquire_opened+0x84/0x110 [nfsd] > kernel: nfs4_get_vfs_file+0x634/0x958 [nfsd] > kernel: nfsd4_process_open2+0xa40/0x1a40 [nfsd] > kernel: nfsd4_open+0xa08/0xe80 [nfsd] > kernel: nfsd4_proc_compound+0xb8c/0x2130 [nfsd] > kernel: nfsd_dispatch+0x22c/0x718 [nfsd] > kernel: svc_process_common+0x8e8/0x1960 [sunrpc] > kernel: svc_process+0x3d4/0x7e0 [sunrpc] > kernel: svc_handle_xprt+0x828/0xe10 [sunrpc] > kernel: svc_recv+0x2cc/0x6a8 [sunrpc] > kernel: nfsd+0x270/0x400 [nfsd] > kernel: kthread+0x288/0x310 > kernel: ret_from_fork+0x10/0x20 >=20 > Proposing to have laundromat thread hold the state_lock over both > marking thru revoking the delegation as well as making free_stateid > acquire state_lock before accessing the list. Making sure that > revoke_delegation() (ie kernel_setlease(unlock)) is called for > every delegation that was revoked and added to the reaper list. >=20 Nice detective work! > CC: stable@vger.kernel.org > Signed-off-by: Olga Kornievskaia >=20 > --- I can't figure out the Fixes: tag. Laundromat's behaviour has > been like that forever. But the free_stateid bits wont apply before > the 1e3577a4521e ("SUNRPC: discard sv_refcnt, and svc_get/svc_put"). > But we used that fixes tag already with a previous fix for a different > problem. > --- > fs/nfsd/nfs4state.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index 9c2b1d251ab3..c97907d7fb38 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -6605,13 +6605,13 @@ nfs4_laundromat(struct nfsd_net *nn) > unhash_delegation_locked(dp, SC_STATUS_REVOKED); > list_add(&dp->dl_recall_lru, &reaplist); > } > - spin_unlock(&state_lock); > while (!list_empty(&reaplist)) { > dp =3D list_first_entry(&reaplist, struct nfs4_delegation, > dl_recall_lru); > list_del_init(&dp->dl_recall_lru); > revoke_delegation(dp); > } > + spin_unlock(&state_lock); > =20 > spin_lock(&nn->client_lock); > while (!list_empty(&nn->close_lru)) { > @@ -7213,7 +7213,9 @@ nfsd4_free_stateid(struct svc_rqst *rqstp, struct n= fsd4_compound_state *cstate, > if (s->sc_status & SC_STATUS_REVOKED) { > spin_unlock(&s->sc_lock); > dp =3D delegstateid(s); > + spin_lock(&state_lock); > list_del_init(&dp->dl_recall_lru); > + spin_unlock(&state_lock); > spin_unlock(&cl->cl_lock); > nfs4_put_stid(s); > ret =3D nfs_ok; I'm not thrilled with this patch, but it does seem like it would fix the problem. Long term, I think we need to get rid of the state_lock, but I don't have a real plan for that just yet as it's not 100% clear what it still protects. As far as a Fixes tag, this bug is likely very old. I'd say it probably got introduced here: 2d4a532d385f nfsd: ensure that clp->cl_revoked list is protected by clp= ->cl_lock In any case, let's go with this patch until we can come up with a better plan for delegation handling. Reviewed-by: Jeff Layton