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Date:   Wed, 21 Aug 2019 10:12:28 -0400
From:   "J. Bruce Fields" <bfields@fieldses.org>
To:     Dan Williams <dan.j.williams@intel.com>
Cc:     Jane Chu <jane.chu@oracle.com>,
        CHUCK_LEVER <chuck.lever@oracle.com>, linux-nfs@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: kernel panic in 5.3-rc5, nfsd_reply_cache_stats_show+0x11
Message-ID: <20190821141228.GA22104@fieldses.org>
References: <72e41dc2-b4cf-a5dd-a365-d26ba1257ef9@oracle.com>
 <CAPcyv4iPuTpk9bifyX5yQxO8gT0fRhYXPrwk-obazWA=Dou3iQ@mail.gmail.com>
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Probably just needs the following.

I've been slow to get some bugfixes upstream, sorry--I'll go send a pull
request now....

--b.

commit 78e70e780b28
Author: He Zhe <zhe.he@windriver.com>
Date:   Tue Aug 6 17:41:04 2019 +0800

    nfsd4: Fix kernel crash when reading proc file reply_cache_stats
    
    reply_cache_stats uses wrong parameter as seq file private structure and
    thus causes the following kernel crash when users read
    /proc/fs/nfsd/reply_cache_stats
    
    BUG: kernel NULL pointer dereference, address: 00000000000001f9
    PGD 0 P4D 0
    Oops: 0000 [#3] SMP PTI
    CPU: 6 PID: 1502 Comm: cat Tainted: G      D           5.3.0-rc3+ #1
    Hardware name: Intel Corporation Broadwell Client platform/Basking Ridge, BIOS BDW-E2R1.86C.0118.R01.1503110618 03/11/2015
    RIP: 0010:nfsd_reply_cache_stats_show+0x3b/0x2d0
    Code: 41 54 49 89 f4 48 89 fe 48 c7 c7 b3 10 33 88 53 bb e8 03 00 00 e8 88 82 d1 ff bf 58 89 41 00 e8 eb c5 85 00 48 83 eb 01 75 f0 <41> 8b 94 24 f8 01 00 00 48 c7 c6 be 10 33 88 4c 89 ef bb e8 03 00
    RSP: 0018:ffffaa520106fe08 EFLAGS: 00010246
    RAX: 000000cfe1a77123 RBX: 0000000000000000 RCX: 0000000000291b46
    RDX: 000000cf00000000 RSI: 0000000000000006 RDI: 0000000000291b28
    RBP: ffffaa520106fe20 R08: 0000000000000006 R09: 000000cfe17e55dd
    R10: ffffa424e47c0000 R11: 000000000000030b R12: 0000000000000001
    R13: ffffa424e5697000 R14: 0000000000000001 R15: ffffa424e5697000
    FS:  00007f805735f580(0000) GS:ffffa424f8f80000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00000000000001f9 CR3: 00000000655ce005 CR4: 00000000003606e0
    Call Trace:
     seq_read+0x194/0x3e0
     __vfs_read+0x1b/0x40
     vfs_read+0x95/0x140
     ksys_read+0x61/0xe0
     __x64_sys_read+0x1a/0x20
     do_syscall_64+0x4d/0x120
     entry_SYSCALL_64_after_hwframe+0x44/0xa9
    RIP: 0033:0x7f805728b861
    Code: fe ff ff 50 48 8d 3d 86 b4 09 00 e8 79 e0 01 00 66 0f 1f 84 00 00 00 00 00 48 8d 05 d9 19 0d 00 8b 00 85 c0 75 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 57 c3 66 0f 1f 44 00 00 48 83 ec 28 48 89 54
    RSP: 002b:00007ffea1ce3c38 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
    RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007f805728b861
    RDX: 0000000000020000 RSI: 00007f8057183000 RDI: 0000000000000003
    RBP: 00007f8057183000 R08: 00007f8057182010 R09: 0000000000000000
    R10: 0000000000000022 R11: 0000000000000246 R12: 0000559a60e8ff10
    R13: 0000000000000003 R14: 0000000000020000 R15: 0000000000020000
    Modules linked in:
    CR2: 00000000000001f9
    ---[ end trace 01613595153f0cba ]---
    RIP: 0010:nfsd_reply_cache_stats_show+0x3b/0x2d0
    Code: 41 54 49 89 f4 48 89 fe 48 c7 c7 b3 10 33 88 53 bb e8 03 00 00 e8 88 82 d1 ff bf 58 89 41 00 e8 eb c5 85 00 48 83 eb 01 75 f0 <41> 8b 94 24 f8 01 00 00 48 c7 c6 be 10 33 88 4c 89 ef bb e8 03 00
    RSP: 0018:ffffaa52004b3e08 EFLAGS: 00010246
    RAX: 0000002bab45a7c6 RBX: 0000000000000000 RCX: 0000000000291b4c
    RDX: 0000002b00000000 RSI: 0000000000000004 RDI: 0000000000291b28
    RBP: ffffaa52004b3e20 R08: 0000000000000004 R09: 0000002bab1c8c7a
    R10: ffffa424e5500000 R11: 00000000000002a9 R12: 0000000000000001
    R13: ffffa424e4475000 R14: 0000000000000001 R15: ffffa424e4475000
    FS:  00007f805735f580(0000) GS:ffffa424f8f80000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00000000000001f9 CR3: 00000000655ce005 CR4: 00000000003606e0
    Killed
    
    Fixes: 3ba75830ce17 ("nfsd4: drc containerization")
    Signed-off-by: He Zhe <zhe.he@windriver.com>
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
index 26ad75ae2be0..96352ab7bd81 100644
--- a/fs/nfsd/nfscache.c
+++ b/fs/nfsd/nfscache.c
@@ -571,7 +571,7 @@ nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data)
  */
 static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
 {
-	struct nfsd_net *nn = v;
+	struct nfsd_net *nn = m->private;
 
 	seq_printf(m, "max entries:           %u\n", nn->max_drc_entries);
 	seq_printf(m, "num entries:           %u\n",