Re: [PATCH] nfsd4: Fix kernel crash when reading proc file reply_cache_stats

["J. Bruce Fields" <bfields@fieldses.org>]

On Tue, Aug 06, 2019 at 05:41:04PM +0800, zhe.he@windriver.com wrote:
> From: He Zhe <zhe.he@windriver.com>
> 
> 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

Thanks, applying for 5.3.

--b.

> 
> 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>
> ---
>  fs/nfsd/nfscache.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
> index 26ad75a..96352ab 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",
> -- 
> 2.7.4