From b0a9d3ab577464529f6649ec54f8a0de160866e3 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Thu, 7 Mar 2013 17:26:18 -0500 Subject: [PATCH] nfsd4: fix race on client shutdown Dropping the session's reference count after the client's means we leave a window where the session's se_client pointer is NULL. An xpt_user callback that encounters such a session may then crash: [ 303.956011] BUG: unable to handle kernel NULL pointer dereference at 0000000000000318 [ 303.959061] IP: [] _raw_spin_lock+0x1e/0x40 [ 303.959061] PGD 37811067 PUD 3d498067 PMD 0 [ 303.959061] Oops: 0002 [#8] PREEMPT SMP [ 303.959061] Modules linked in: md5 nfsd auth_rpcgss nfs_acl snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_page_alloc microcode psmouse snd_timer serio_raw pcspkr evdev snd soundcore i2c_piix4 i2c_core intel_agp intel_gtt processor button nfs lockd sunrpc fscache ata_generic pata_acpi ata_piix uhci_hcd libata btrfs usbcore usb_common crc32c scsi_mod libcrc32c zlib_deflate floppy virtio_balloon virtio_net virtio_pci virtio_blk virtio_ring virtio [ 303.959061] CPU 0 [ 303.959061] Pid: 264, comm: nfsd Tainted: G D 3.8.0-ARCH+ #156 Bochs Bochs [ 303.959061] RIP: 0010:[] [] _raw_spin_lock+0x1e/0x40 [ 303.959061] RSP: 0018:ffff880037877dd8 EFLAGS: 00010202 [ 303.959061] RAX: 0000000000000100 RBX: ffff880037a2b698 RCX: ffff88003d879278 [ 303.959061] RDX: ffff88003d879278 RSI: dead000000100100 RDI: 0000000000000318 [ 303.959061] RBP: ffff880037877dd8 R08: ffff88003c5a0f00 R09: 0000000000000002 [ 303.959061] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 [ 303.959061] R13: 0000000000000318 R14: ffff880037a2b680 R15: ffff88003c1cbe00 [ 303.959061] FS: 0000000000000000(0000) GS:ffff88003fc00000(0000) knlGS:0000000000000000 [ 303.959061] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 303.959061] CR2: 0000000000000318 CR3: 000000003d49c000 CR4: 00000000000006f0 [ 303.959061] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 303.959061] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 303.959061] Process nfsd (pid: 264, threadinfo ffff880037876000, task ffff88003c1fd0a0) [ 303.959061] Stack: [ 303.959061] ffff880037877e08 ffffffffa03772ec ffff88003d879000 ffff88003d879278 [ 303.959061] ffff88003d879080 0000000000000000 ffff880037877e38 ffffffffa0222a1f [ 303.959061] 0000000000107ac0 ffff88003c22e000 ffff88003d879000 ffff88003c1cbe00 [ 303.959061] Call Trace: [ 303.959061] [] nfsd4_conn_lost+0x3c/0xa0 [nfsd] [ 303.959061] [] svc_delete_xprt+0x10f/0x180 [sunrpc] [ 303.959061] [] svc_recv+0xe6/0x580 [sunrpc] [ 303.959061] [] nfsd+0xb5/0x140 [nfsd] [ 303.959061] [] ? nfsd_destroy+0x90/0x90 [nfsd] [ 303.959061] [] kthread+0xc0/0xd0 [ 303.959061] [] ? perf_trace_xen_mmu_set_pte_at+0x50/0x100 [ 303.959061] [] ? kthread_freezable_should_stop+0x70/0x70 [ 303.959061] [] ret_from_fork+0x7c/0xb0 [ 303.959061] [] ? kthread_freezable_should_stop+0x70/0x70 [ 303.959061] Code: ff ff 5d c3 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 55 65 48 8b 04 25 f0 c6 00 00 48 89 e5 83 80 44 e0 ff ff 01 b8 00 01 00 00 <3e> 66 0f c1 07 0f b6 d4 38 c2 74 0f 66 0f 1f 44 00 00 f3 90 0f [ 303.959061] RIP [] _raw_spin_lock+0x1e/0x40 [ 303.959061] RSP [ 303.959061] CR2: 0000000000000318 [ 304.001218] ---[ end trace 2d809cd4a7931f5a ]--- [ 304.001903] note: nfsd[264] exited with preempt_count 2 Reported-by: Bryan Schumaker Signed-off-by: J. Bruce Fields --- fs/nfsd/nfs4state.c | 12 ++++++++---- fs/nfsd/nfs4xdr.c | 1 - fs/nfsd/state.h | 2 -- 3 files changed, 8 insertions(+), 7 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 2e27430b9070..3e5cbfe8a967 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -864,7 +864,7 @@ static void free_session(struct kref *kref) __free_session(ses); } -void nfsd4_put_session(struct nfsd4_session *ses) +static void nfsd4_put_session(struct nfsd4_session *ses) { struct nfsd_net *nn = net_generic(ses->se_client->net, nfsd_net_id); @@ -1057,12 +1057,16 @@ release_session_client(struct nfsd4_session *session) struct nfs4_client *clp = session->se_client; struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id); + nfsd4_put_session(session); if (!atomic_dec_and_lock(&clp->cl_refcount, &nn->client_lock)) return; - if (is_client_expired(clp)) { + /* + * At this point we also know all sessions have refcnt 1, + * so free_client will delete them all if necessary: + */ + if (is_client_expired(clp)) free_client(clp); - session->se_client = NULL; - } else + else renew_client_locked(clp); spin_unlock(&nn->client_lock); } diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c index 229b3ac246e1..9b02b6652f2b 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -3685,7 +3685,6 @@ nfs4svc_encode_compoundres(struct svc_rqst *rqstp, __be32 *p, struct nfsd4_compo } /* Renew the clientid on success and on replay */ release_session_client(cs->session); - nfsd4_put_session(cs->session); } return 1; } diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index 1a8c7391f7ae..327552bb6dba 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -209,8 +209,6 @@ struct nfsd4_session { struct nfsd4_slot *se_slots[]; /* forward channel slots */ }; -extern void nfsd4_put_session(struct nfsd4_session *ses); - /* formatted contents of nfs4_sessionid */ struct nfsd4_sessionid { clientid_t clientid; -- 2.30.2