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 5C72239B949; Fri, 22 May 2026 12:29:23 +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=1779452964; cv=none; b=oCOTLXHRTo2TZoXHqRvxAGpqidYEsWeulsqkkXN6WemPfRbC5JorZu/FbcS59U4rY+s1NY8cA5Ff+2MeRHvKc5UetUbQ6KbgZXa38WF95+CL4Z3/eZnDX+gVIJCDD1cEH8qr2wDH/NNZF/goaxLKHrBu29hN3OwSt23D/rrICxs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779452964; c=relaxed/simple; bh=Q9R3lexVfgStfNvJhEKl9Rwa8CS4i6Du2SQCwWtLH2o=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=HDj0Q73NiMKMama8EZBrXZuOX8PTVXj/5iTGHdE8sPJbxlduaqhx8fmnBMBsFCfRY3VF8Dx+3Uh817snZz1UgaLNZcqlUra9U9Hzd+dIHq/4og9tEW5LZr4j0In8IOqRp+KuoVPXZytr4BMFZwCgtS4xACmueuRRN2ELI5QzVuY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JYCaQiBe; 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="JYCaQiBe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9057D1F00A3F; Fri, 22 May 2026 12:29:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779452963; bh=vAsVyAMM+J0ncv0+jrvSeuHqV77JmQRnTLfS+JhnXVA=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=JYCaQiBeV1AP/v/bD1G4jlVFFCo35aQgAolMJvSymGHmmElxbWnCzrC9DQZRJF/+C nIwInCR0ACWo4lYlbnwD9j/HmKvofP0q/4fKAJS4cfp5ph92KGjkHAby8+LHZK3Ov8 fArtyKZ/yxfwPUdkCwsSInHEj2TqT0DgBgaZhGggBp10OVjGfad52LJ/Io7kCUGa/9 Fsl4+0Y9m1hVi5FMyVuD5Wt7NwxBRFUDwyZ+iUBZ/2/eBcNu+xEOiJ+U3UOma2pxOL WbPUBjg31H/sWHc3q6YJgfHQuV3qZvj1kfJcfezQzcg0P+gcUB+1Ii7KEo6JejtX6m BVumxeefwxx7w== From: Jeff Layton Date: Fri, 22 May 2026 08:28:57 -0400 Subject: [PATCH v4 08/21] nfsd: use RCU to protect fi_deleg_file Precedence: bulk X-Mailing-List: linux-doc@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: <20260522-dir-deleg-v4-8-2acb883ac6bc@kernel.org> References: <20260522-dir-deleg-v4-0-2acb883ac6bc@kernel.org> In-Reply-To: <20260522-dir-deleg-v4-0-2acb883ac6bc@kernel.org> To: Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , Trond Myklebust , Anna Schumaker Cc: Alexander Aring , Amir Goldstein , Jan Kara , Alexander Viro , Christian Brauner , Calum Mackay , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-nfs@vger.kernel.org, Jeff Layton X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=7836; i=jlayton@kernel.org; h=from:subject:message-id; bh=Q9R3lexVfgStfNvJhEKl9Rwa8CS4i6Du2SQCwWtLH2o=; b=owEBbQKS/ZANAwAKAQAOaEEZVoIVAcsmYgBqEEwPYE0G8u59cPwldvM5DKO8n5SWbxIF760cW 1cVXNNPN7mJAjMEAAEKAB0WIQRLwNeyRHGyoYTq9dMADmhBGVaCFQUCahBMDwAKCRAADmhBGVaC FSBYD/9iUfosgEKcLkXVBIk+Ab9aUqaUulnqu8Iv9mtjtZdcfBLNFbk8Qvaj0Epao5U9C702LMD iUP8lgThqj/3xYX8NumU16o6IF33Eqa7j3dQjsn4eHKa2pVA7+QB7z5q6PjtVeA9S0MiSpg25Aj HcJXkX/XEDs+s71ziqGeTNPxFMT2oz0MmHPqNqHGvoD4YgjiJN2VgmO2BSsYglzyZ/+y+nxbEw5 3tF/QWKIRB/zvAju+lulwpzE9GYKi5C71Wsi2FeTrVvOsFMxGv53pU9JDPe7KWSZISixnkVc/aj FA3tQnlCkdpWMfqsnOqHkiQ0AcUkumCDMARSq/zNjwcs0fcCcjwjDecCy1+hsXunqoMARCQMjlJ H9H9KTu/TSORGTz3nOiP5ePWhLSMOlj7R5umzYltsORB3O9bB/jR4Pa05ryjWPOosTqMIxz+qFH a1yzMzz1e7EhKHUiMO/VZV5eEQJCu0HdU6IBWUNSBthpJsSMcNK1WdSJGQb74H3kYPgmenRwa5V aFl/rHKEXvDsIBm66sw/gOUUgUngJ7mvpf6HKBGoKGET8UcVDYLNNKsigJXUtKC26DCoJTo4nGg 5xeiFQtUA5//LXqA6eG5L7wX44ie4cBjkfCGyrtfrDtEIgcB3aGGX7zvA7x2XiGJVBMY4Xxc5bd WT8E6dV3w9dEBdQ== X-Developer-Key: i=jlayton@kernel.org; a=openpgp; fpr=4BC0D7B24471B2A184EAF5D3000E684119568215 fi_deleg_file can be NULLed by put_deleg_file() when fi_delegees drops to zero during delegation teardown (e.g. DELEGRETURN). Concurrent accesses from workqueue callbacks -- such as CB_NOTIFY -- can dereference a NULL pointer if they race with this teardown. Annotate fi_deleg_file with __rcu and convert all accessors to use proper RCU primitives: - rcu_assign_pointer() / RCU_INIT_POINTER() for stores - rcu_dereference_protected() for reads under fi_lock or where fi_delegees > 0 guarantees stability This prepares for a subsequent patch that will use rcu_read_lock + rcu_dereference + nfsd_file_get to safely acquire a reference from the CB_NOTIFY callback path without holding fi_lock. Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Jeff Layton --- fs/nfsd/nfs4layouts.c | 2 +- fs/nfsd/nfs4state.c | 40 ++++++++++++++++++++++++---------------- fs/nfsd/state.h | 2 +- 3 files changed, 26 insertions(+), 18 deletions(-) diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c index e3984c90792e..9ed2e3d65062 100644 --- a/fs/nfsd/nfs4layouts.c +++ b/fs/nfsd/nfs4layouts.c @@ -248,7 +248,7 @@ nfsd4_alloc_layout_stateid(struct nfsd4_compound_state *cstate, NFSPROC4_CLNT_CB_LAYOUT); if (parent->sc_type == SC_TYPE_DELEG) - ls->ls_file = nfsd_file_get(fp->fi_deleg_file); + ls->ls_file = nfsd_file_get(rcu_dereference_protected(fp->fi_deleg_file, 1)); else ls->ls_file = find_any_file(fp); BUG_ON(!ls->ls_file); diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index beb6e95a1e4d..c7019cd07a91 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1212,7 +1212,9 @@ static void put_deleg_file(struct nfs4_file *fp) spin_lock(&fp->fi_lock); if (--fp->fi_delegees == 0) { - swap(nf, fp->fi_deleg_file); + nf = rcu_dereference_protected(fp->fi_deleg_file, + lockdep_is_held(&fp->fi_lock)); + rcu_assign_pointer(fp->fi_deleg_file, NULL); swap(rnf, fp->fi_rdeleg_file); } spin_unlock(&fp->fi_lock); @@ -1281,7 +1283,7 @@ static void nfsd_fsnotify_recalc_mask(struct nfsd_file *nf) static void nfs4_unlock_deleg_lease(struct nfs4_delegation *dp) { struct nfs4_file *fp = dp->dl_stid.sc_file; - struct nfsd_file *nf = fp->fi_deleg_file; + struct nfsd_file *nf = rcu_dereference_protected(fp->fi_deleg_file, 1); WARN_ON_ONCE(!fp->fi_delegees); @@ -3175,7 +3177,8 @@ static int nfs4_show_deleg(struct seq_file *s, struct nfs4_stid *st) /* XXX: lease time, whether it's being recalled. */ spin_lock(&nf->fi_lock); - file = nf->fi_deleg_file; + file = rcu_dereference_protected(nf->fi_deleg_file, + lockdep_is_held(&nf->fi_lock)); if (file) { seq_puts(s, ", "); nfs4_show_superblock(s, file); @@ -4957,7 +4960,7 @@ static void nfsd4_file_init(const struct svc_fh *fh, struct nfs4_file *fp) INIT_LIST_HEAD(&fp->fi_delegations); INIT_LIST_HEAD(&fp->fi_clnt_odstate); fh_copy_shallow(&fp->fi_fhandle, &fh->fh_handle); - fp->fi_deleg_file = NULL; + RCU_INIT_POINTER(fp->fi_deleg_file, NULL); fp->fi_rdeleg_file = NULL; fp->fi_had_conflict = false; fp->fi_share_deny = 0; @@ -6109,7 +6112,7 @@ static struct file_lease *nfs4_alloc_init_lease(struct nfs4_delegation *dp, u32 fl->c.flc_type = deleg_is_read(dp->dl_type) ? F_RDLCK : F_WRLCK; fl->c.flc_owner = (fl_owner_t)dp; fl->c.flc_pid = current->tgid; - fl->c.flc_file = dp->dl_stid.sc_file->fi_deleg_file->nf_file; + fl->c.flc_file = rcu_dereference_protected(dp->dl_stid.sc_file->fi_deleg_file, 1)->nf_file; return fl; } @@ -6117,7 +6120,7 @@ static int nfsd4_check_conflicting_opens(struct nfs4_client *clp, struct nfs4_file *fp) { struct nfs4_ol_stateid *st; - struct file *f = fp->fi_deleg_file->nf_file; + struct file *f = rcu_dereference_protected(fp->fi_deleg_file, 1)->nf_file; struct inode *ino = file_inode(f); int writes; @@ -6194,7 +6197,7 @@ nfsd4_verify_deleg_dentry(struct nfsd4_open *open, struct nfs4_file *fp, exp_put(exp); dput(child); - if (child != file_dentry(fp->fi_deleg_file->nf_file)) + if (child != file_dentry(rcu_dereference_protected(fp->fi_deleg_file, 1)->nf_file)) return -EAGAIN; return 0; @@ -6300,8 +6303,9 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, status = -EAGAIN; else if (nfsd4_verify_setuid_write(open, nf)) status = -EAGAIN; - else if (!fp->fi_deleg_file) { - fp->fi_deleg_file = nf; + else if (!rcu_dereference_protected(fp->fi_deleg_file, + lockdep_is_held(&fp->fi_lock))) { + rcu_assign_pointer(fp->fi_deleg_file, nf); /* increment early to prevent fi_deleg_file from being * cleared */ fp->fi_delegees = 1; @@ -6326,7 +6330,7 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, if (!fl) goto out_clnt_odstate; - status = kernel_setlease(fp->fi_deleg_file->nf_file, + status = kernel_setlease(rcu_dereference_protected(fp->fi_deleg_file, 1)->nf_file, fl->c.flc_type, &fl, NULL); if (fl) locks_free_lease(fl); @@ -6347,7 +6351,7 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, * Now that the deleg is set, check again to ensure that nothing * raced in and changed the mode while we weren't looking. */ - status = nfsd4_verify_setuid_write(open, fp->fi_deleg_file); + status = nfsd4_verify_setuid_write(open, rcu_dereference_protected(fp->fi_deleg_file, 1)); if (status) goto out_unlock; @@ -6368,7 +6372,8 @@ nfs4_set_delegation(struct nfsd4_open *open, struct nfs4_ol_stateid *stp, return dp; out_unlock: - kernel_setlease(fp->fi_deleg_file->nf_file, F_UNLCK, NULL, (void **)&dp); + kernel_setlease(rcu_dereference_protected(fp->fi_deleg_file, 1)->nf_file, + F_UNLCK, NULL, (void **)&dp); out_clnt_odstate: put_clnt_odstate(dp->dl_clnt_odstate); nfs4_put_stid(&dp->dl_stid); @@ -6525,8 +6530,9 @@ nfs4_open_delegation(struct svc_rqst *rqstp, struct nfsd4_open *open, memcpy(&open->op_delegate_stateid, &dp->dl_stid.sc_stateid, sizeof(dp->dl_stid.sc_stateid)); if (open->op_share_access & NFS4_SHARE_ACCESS_WRITE) { - struct file *f = dp->dl_stid.sc_file->fi_deleg_file->nf_file; + struct file *f; + f = rcu_dereference_protected(dp->dl_stid.sc_file->fi_deleg_file, 1)->nf_file; if (!nfsd4_add_rdaccess_to_wrdeleg(rqstp, open, fh, stp) || !nfs4_delegation_stat(dp, currentfh, &stat)) { nfs4_put_stid(&dp->dl_stid); @@ -9668,8 +9674,9 @@ nfsd_get_dir_deleg(struct nfsd4_compound_state *cstate, /* existing delegation? */ if (nfs4_delegation_exists(clp, fp)) { status = -EAGAIN; - } else if (!fp->fi_deleg_file) { - fp->fi_deleg_file = nfsd_file_get(nf); + } else if (!rcu_dereference_protected(fp->fi_deleg_file, + lockdep_is_held(&fp->fi_lock))) { + rcu_assign_pointer(fp->fi_deleg_file, nfsd_file_get(nf)); fp->fi_delegees = 1; } else { ++fp->fi_delegees; @@ -9721,7 +9728,8 @@ nfsd_get_dir_deleg(struct nfsd4_compound_state *cstate, } /* Something failed. Drop the lease and clean up the stid */ - kernel_setlease(fp->fi_deleg_file->nf_file, F_UNLCK, NULL, (void **)&dp); + kernel_setlease(rcu_dereference_protected(fp->fi_deleg_file, 1)->nf_file, + F_UNLCK, NULL, (void **)&dp); out_put_stid: nfs4_put_stid(&dp->dl_stid); out_delegees: diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index 790282781243..9c6e2e7abc82 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -698,7 +698,7 @@ struct nfs4_file { */ atomic_t fi_access[2]; u32 fi_share_deny; - struct nfsd_file *fi_deleg_file; + struct nfsd_file __rcu *fi_deleg_file; struct nfsd_file *fi_rdeleg_file; int fi_delegees; struct knfsd_fh fi_fhandle; -- 2.54.0