[Cluster-devel] [PATCH dlm/next 01/18] fs: dlm: avoid false-positive checker warning

[Alexander Aring]

This patch avoid the false-positive checker warning about writing 112
bytes into a 88 bytes field "e->request", see:

[   54.891560] dlm: csmb1: dlm_recover_directory 23 out 2 messages
[   54.990542] ------------[ cut here ]------------
[   54.991012] memcpy: detected field-spanning write (size 112) of single field "&e->request" at fs/dlm/requestqueue.c:47 (size 88)
[   54.992150] WARNING: CPU: 0 PID: 297 at fs/dlm/requestqueue.c:47 dlm_add_requestqueue+0x177/0x180
[   54.993002] CPU: 0 PID: 297 Comm: kworker/u4:3 Not tainted 6.1.0-rc5-00008-ge01d50cbd6ee #248
[   54.993878] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.0-1.fc36 04/01/2014
[   54.994718] Workqueue: dlm_recv process_recv_sockets
[   54.995230] RIP: 0010:dlm_add_requestqueue+0x177/0x180
[   54.995731] Code: e7 01 0f 85 3b ff ff ff b9 58 00 00 00 48 c7 c2 c0 41 74 82 4c 89 ee 48 c7 c7 20 42 74 82 c6 05 8b 8d 30 02 01 e8 51 07 be 00 <0f> 0b e9 12 ff ff ff 66 90 0f 1f 44 00 00 41 57 48 8d 87 10 08 00
[   54.997483] RSP: 0018:ffffc90000b1fbe8 EFLAGS: 00010282
[   54.997990] RAX: 0000000000000000 RBX: ffff888024fc3d00 RCX: 0000000000000000
[   54.998667] RDX: 0000000000000001 RSI: ffffffff81155014 RDI: fffff52000163f73
[   54.999342] RBP: ffff88800dbac000 R08: 0000000000000001 R09: ffffc90000b1fa5f
[   54.999997] R10: fffff52000163f4b R11: 203a7970636d656d R12: ffff88800cfb0018
[   55.000673] R13: 0000000000000070 R14: ffff888024fc3d18 R15: 0000000000000000
[   55.001344] FS:  0000000000000000(0000) GS:ffff88806d600000(0000) knlGS:0000000000000000
[   55.002078] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   55.002603] CR2: 00007f35d4f0b9a0 CR3: 0000000025495002 CR4: 0000000000770ef0
[   55.003258] PKRU: 55555554
[   55.003514] Call Trace:
[   55.003756]  <TASK>
[   55.003953]  dlm_receive_buffer+0x1c0/0x200
[   55.004348]  dlm_process_incoming_buffer+0x46d/0x780
[   55.004786]  ? kernel_recvmsg+0x8b/0xc0
[   55.005150]  receive_from_sock.isra.0+0x168/0x420
[   55.005582]  ? process_listen_recv_socket+0x10/0x10
[   55.006018]  ? finish_task_switch.isra.0+0xe0/0x400
[   55.006469]  ? __switch_to+0x2fe/0x6a0
[   55.006808]  ? read_word_at_a_time+0xe/0x20
[   55.007197]  ? strscpy+0x146/0x190
[   55.007505]  process_one_work+0x3d0/0x6b0
[   55.007863]  worker_thread+0x8d/0x620
[   55.008209]  ? __kthread_parkme+0xd8/0xf0
[   55.008565]  ? process_one_work+0x6b0/0x6b0
[   55.008937]  kthread+0x171/0x1a0
[   55.009251]  ? kthread_exit+0x60/0x60
[   55.009582]  ret_from_fork+0x1f/0x30
[   55.009903]  </TASK>
[   55.010120] ---[ end trace 0000000000000000 ]---
[   55.025783] dlm: csmb1: dlm_recover 5 generation 3 done: 201 ms
[   55.026466] gfs2: fsid=smbcluster:csmb1.0: recover generation 3 done

It seems the checker is unable to detect the additional length bytes
which was allocated additionally for the flexible array in struct
dlm_message. To solve it we split the memcpy() into copy for the 88 bytes
struct and another memcpy() for the flexible array m_extra field.

Signed-off-by: Alexander Aring <aahringo at redhat.com>
---
 fs/dlm/requestqueue.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/dlm/requestqueue.c b/fs/dlm/requestqueue.c
index 036a9a0078f6..8be2893ad15b 100644
--- a/fs/dlm/requestqueue.c
+++ b/fs/dlm/requestqueue.c
@@ -44,7 +44,8 @@ void dlm_add_requestqueue(struct dlm_ls *ls, int nodeid, struct dlm_message *ms)
 
 	e->recover_seq = ls->ls_recover_seq & 0xFFFFFFFF;
 	e->nodeid = nodeid;
-	memcpy(&e->request, ms, le16_to_cpu(ms->m_header.h_length));
+	memcpy(&e->request, ms, sizeof(*ms));
+	memcpy(&e->request.m_extra, ms->m_extra, length);
 
 	atomic_inc(&ls->ls_requestqueue_cnt);
 	mutex_lock(&ls->ls_requestqueue_mutex);
-- 
2.31.1