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From:   Zheyu Ma <zheyuma97@gmail.com>
To:     hare@kernel.org, jejb@linux.ibm.com, martin.petersen@oracle.com
Cc:     linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Zheyu Ma <zheyuma97@gmail.com>
Subject: [PATCH] scsi: myrs: add a check against null pointer dereference
Date:   Mon, 14 Jun 2021 09:25:04 +0000
Message-Id: <1623662704-10139-1-git-send-email-zheyuma97@gmail.com>
Precedence: bulk

In the process of driver loading, the driver may fail at the place of
'myrs_enable_mmio_mbox', resulting in calling the 'myrs_cleanup'
function, but at this time, 'cs->disable' has not been assigned, so a
null pointer dereference is caused.

Fix this by check whether 'cs->disable_intr' is a null pointer.

This log reveals it:

[    2.777884] BUG: kernel NULL pointer dereference, address: 0000000000000000
[    2.778357] #PF: supervisor instruction fetch in kernel mode
[    2.778742] #PF: error_code(0x0010) - not-present page
[    2.779093] PGD 0 P4D 0
[    2.779272] Oops: 0010 [#1] PREEMPT SMP PTI
[    2.779560] CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.12.4-g70e7f0549188-dirty #103
[    2.780090] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
[    2.780885] RIP: 0010:0x0
[    2.781077] Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
[    2.781538] RSP: 0000:ffffc90000017b60 EFLAGS: 00010293
[    2.781893] RAX: ffff8881001e0000 RBX: ffff888107a7cdb0 RCX: 0000000000000000
[    2.782376] RDX: 0000000000000000 RSI: ffffffff824409c6 RDI: ffff888107a7cdb0
[    2.782803] RBP: ffffc90000017b80 R08: 0000000000000001 R09: 0000000000000001
[    2.782803] R10: 0000000000000000 R11: 0000000000000001 R12: ffff888101c34000
[    2.782803] R13: ffff888007840000 R14: ffffc90000091000 R15: ffffffff82443300
[    2.782803] FS:  0000000000000000(0000) GS:ffff88817bcc0000(0000) knlGS:0000000000000000
[    2.782803] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.782803] CR2: ffffffffffffffd6 CR3: 0000000005e2e000 CR4: 00000000000006e0
[    2.782803] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    2.782803] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    2.782803] Call Trace:
[    2.782803]  myrs_cleanup+0x10f/0x190
[    2.782803]  myrs_probe+0x839/0xa20
[    2.782803]  ? kcov_remote_start+0x17b/0x430
[    2.782803]  ? trace_hardirqs_on+0x55/0x130
[    2.782803]  ? _raw_spin_unlock_irqrestore+0x35/0x5d
[    2.782803]  local_pci_probe+0x4a/0xb0
[    2.782803]  ? local_pci_probe+0x4a/0xb0
[    2.782803]  pci_device_probe+0x126/0x1d0
[    2.782803]  ? pci_device_remove+0x100/0x100
[    2.782803]  really_probe+0x27e/0x650
[    2.782803]  driver_probe_device+0x84/0x1d0
[    2.782803]  ? mutex_lock_nested+0x16/0x20
[    2.782803]  device_driver_attach+0x63/0x70
[    2.782803]  __driver_attach+0x117/0x1a0
[    2.782803]  ? device_driver_attach+0x70/0x70
[    2.782803]  bus_for_each_dev+0xb6/0x110
[    2.782803]  ? rdinit_setup+0x40/0x40
[    2.782803]  driver_attach+0x22/0x30
[    2.782803]  bus_add_driver+0x1e6/0x2a0
[    2.782803]  driver_register+0xa4/0x180
[    2.782803]  __pci_register_driver+0x77/0x80
[    2.782803]  ? myrb_init_module+0x62/0x62
[    2.782803]  myrs_init_module+0x41/0x62
[    2.782803]  do_one_initcall+0x7a/0x3d0
[    2.782803]  ? rdinit_setup+0x40/0x40
[    2.782803]  ? rcu_read_lock_sched_held+0x4a/0x70
[    2.782803]  kernel_init_freeable+0x2a7/0x2f9
[    2.782803]  ? rest_init+0x2c0/0x2c0
[    2.782803]  kernel_init+0x13/0x180
[    2.782803]  ? rest_init+0x2c0/0x2c0
[    2.782803]  ? rest_init+0x2c0/0x2c0
[    2.782803]  ret_from_fork+0x1f/0x30
[    2.782803] Modules linked in:
[    2.782803] Dumping ftrace buffer:
[    2.782803]    (ftrace buffer empty)
[    2.782803] CR2: 0000000000000000
[    2.782803] ---[ end trace c5cb7be94bce994d ]---
[    2.782803] RIP: 0010:0x0
[    2.782803] Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
[    2.782803] RSP: 0000:ffffc90000017b60 EFLAGS: 00010293
[    2.782803] RAX: ffff8881001e0000 RBX: ffff888107a7cdb0 RCX: 0000000000000000
[    2.782803] RDX: 0000000000000000 RSI: ffffffff824409c6 RDI: ffff888107a7cdb0
[    2.782803] RBP: ffffc90000017b80 R08: 0000000000000001 R09: 0000000000000001
[    2.782803] R10: 0000000000000000 R11: 0000000000000001 R12: ffff888101c34000
[    2.782803] R13: ffff888007840000 R14: ffffc90000091000 R15: ffffffff82443300
[    2.782803] FS:  0000000000000000(0000) GS:ffff88817bcc0000(0000) knlGS:0000000000000000
[    2.782803] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.782803] CR2: ffffffffffffffd6 CR3: 0000000005e2e000 CR4: 00000000000006e0
[    2.782803] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[    2.782803] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[    2.782803] Kernel panic - not syncing: Fatal exception
[    2.782803] Dumping ftrace buffer:
[    2.782803]    (ftrace buffer empty)
[    2.782803] Kernel Offset: disabled
[    2.782803] Rebooting in 1 seconds..

Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
---
 drivers/scsi/myrs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/myrs.c b/drivers/scsi/myrs.c
index 3b68c68d1716..875ef60ebdd0 100644
--- a/drivers/scsi/myrs.c
+++ b/drivers/scsi/myrs.c
@@ -2268,8 +2268,10 @@ static void myrs_cleanup(struct myrs_hba *cs)
 	/* Free the memory mailbox, status, and related structures */
 	myrs_unmap(cs);
 
-	if (cs->mmio_base) {
+	if (cs->disable_intr)
 		cs->disable_intr(cs);
+
+	if (cs->mmio_base) {
 		iounmap(cs->mmio_base);
 		cs->mmio_base = NULL;
 	}
-- 
2.17.6