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From:   Zheyu Ma <zheyuma97@gmail.com>
To:     gregkh@linuxfoundation.org, jirislaby@kernel.org
Cc:     zheyuma97@gmail.com, linux-serial@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v3] tty: serial: jsm: allocate queue buffer at probe time
Date:   Wed, 16 Jun 2021 02:39:51 +0000
Message-Id: <1623811191-13952-1-git-send-email-zheyuma97@gmail.com>
Precedence: bulk

In function 'neo_intr', the driver uses 'ch->ch_equeue' and
'ch->ch_reuque'. These two pointers are initialized in 'jsm_tty_open',
but the interrupt handler 'neo_intr' has been registered in the probe
progress. If 'jsm_tty_open' has not been called at this time, it will
cause null pointer dereference.

Once the driver registers the interrupt handler, the driver should be
ready to handle it.

Fix this by allocating the memory at probe time and not at open time.

This log reveals it:

[   12.771912] BUG: kernel NULL pointer dereference, address: 0000000000000000
[   12.774932] #PF: supervisor write access in kernel mode
[   12.775314] #PF: error_code(0x0002) - not-present page
[   12.775689] PGD 0 P4D 0
[   12.775881] Oops: 0002 [#1] PREEMPT SMP PTI
[   12.776212] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.12.4-g70e7f0549188-dirty #106
[   12.776803] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
[   12.777627] RIP: 0010:memcpy_fromio+0x75/0xa0
[   12.777983] Code: e9 02 f3 a5 41 f6 c5 02 74 02 66 a5 41 f6 c5 01 74 01 a4 e8 5d 4e 6b ff 5b 41 5c 41 5d 5d c3 e8 51 4e 6b ff 4c 89 e7 48 89 de <a4> 49 89 fc 48 89 f3 49 83 ed 01 eb a4 e8 39 4e 6b ff 4c 89 e7 48
[   12.779377] RSP: 0018:ffffc90000118db0 EFLAGS: 00010046
[   12.779771] RAX: ffff888100258000 RBX: ffffc90007d0010f RCX: 0000000000000000
[   12.780298] RDX: 0000000000000000 RSI: ffffc90007d0010f RDI: 0000000000000000
[   12.780820] RBP: ffffc90000118dc8 R08: 0000000000000000 R09: 0000000000000000
[   12.781359] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
[   12.781928] R13: 0000000000000001 R14: 0000000007d0009e R15: 0000000000000000
[   12.782453] FS:  0000000000000000(0000) GS:ffff88817bc80000(0000) knlGS:0000000000000000
[   12.783067] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   12.783499] CR2: 0000000000000000 CR3: 0000000005e2e000 CR4: 00000000000006e0
[   12.784051] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   12.784579] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   12.785105] Call Trace:
[   12.785295]  <IRQ>
[   12.785457]  neo_copy_data_from_uart_to_queue+0x2f7/0x4e0
[   12.785871]  neo_parse_isr.part.4+0x175/0x4d0
[   12.786217]  neo_intr+0x188/0x7a0
[   12.786478]  __handle_irq_event_percpu+0x53/0x3e0
[   12.786831]  handle_irq_event_percpu+0x35/0x90
[   12.787157]  handle_irq_event+0x39/0x60
[   12.787458]  handle_fasteoi_irq+0xc2/0x1d0
[   12.787763]  __common_interrupt+0x7f/0x150
[   12.788071]  common_interrupt+0xb4/0xd0
[   12.788358]  </IRQ>
[   12.788532]  asm_common_interrupt+0x1e/0x40
[   12.788853] RIP: 0010:native_safe_halt+0x17/0x20
[   12.789199] Code: 07 0f 00 2d 0b ab 50 00 f4 5d c3 0f 1f 84 00 00 00 00 00 8b 05 f2 11 f7 01 55 48 89 e5 85 c0 7e 07 0f 00 2d eb aa 50 00 fb f4 <5d> c3 cc cc cc cc cc cc cc 55 48 89 e5 e8 67 53 ff ff 8b 0d e9 dc
[   12.790581] RSP: 0018:ffffc9000008fe90 EFLAGS: 00000246
[   12.790975] RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000000000
[   12.791502] RDX: 0000000000000000 RSI: ffffffff859d2c94 RDI: ffffffff8589953e
[   12.792031] RBP: ffffc9000008fe90 R08: 0000000000000001 R09: 0000000000000001
[   12.792573] R10: 0000000000000000 R11: 0000000000000001 R12: ffffffff86434488
[   12.793095] R13: 0000000000000000 R14: 0000000000000000 R15: ffff888100258000
[   12.793625]  default_idle+0x9/0x10
[   12.793898]  arch_cpu_idle+0xa/0x10
[   12.794159]  default_idle_call+0x6e/0x250
[   12.794462]  do_idle+0x1f0/0x2d0
[   12.794708]  cpu_startup_entry+0x18/0x20
[   12.795008]  start_secondary+0x11f/0x160
[   12.795314]  secondary_startup_64_no_verify+0xb0/0xbb
[   12.795701] Modules linked in:
[   12.795931] Dumping ftrace buffer:
[   12.796206]    (ftrace buffer empty)
[   12.796481] CR2: 0000000000000000
[   12.796741] ---[ end trace 5535b8755359e59f ]---
[   12.797089] RIP: 0010:memcpy_fromio+0x75/0xa0
[   12.797417] Code: e9 02 f3 a5 41 f6 c5 02 74 02 66 a5 41 f6 c5 01 74 01 a4 e8 5d 4e 6b ff 5b 41 5c 41 5d 5d c3 e8 51 4e 6b ff 4c 89 e7 48 89 de <a4> 49 89 fc 48 89 f3 49 83 ed 01 eb a4 e8 39 4e 6b ff 4c 89 e7 48
[   12.798787] RSP: 0018:ffffc90000118db0 EFLAGS: 00010046
[   12.799175] RAX: ffff888100258000 RBX: ffffc90007d0010f RCX: 0000000000000000
[   12.799702] RDX: 0000000000000000 RSI: ffffc90007d0010f RDI: 0000000000000000
[   12.800226] RBP: ffffc90000118dc8 R08: 0000000000000000 R09: 0000000000000000
[   12.800753] R10: 0000000000000000 R11: 0000000000000001 R12: 0000000000000000
[   12.801287] R13: 0000000000000001 R14: 0000000007d0009e R15: 0000000000000000
[   12.801809] FS:  0000000000000000(0000) GS:ffff88817bc80000(0000) knlGS:0000000000000000
[   12.802431] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   12.802862] CR2: 0000000000000000 CR3: 0000000005e2e000 CR4: 00000000000006e0
[   12.803412] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   12.803932] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   12.804447] Kernel panic - not syncing: Fatal exception in interrupt
[   12.805067] Dumping ftrace buffer:
[   12.805315]    (ftrace buffer empty)
[   12.805584] Kernel Offset: disabled
[   12.805850] Rebooting in 1 seconds..

Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
---
Changes in v3:
    - Remove useless comments
    - Remove uncessary flag changes
    - Keep flushing input quques in the open function

Changes in v2:
    - Allocate the memory at probe time, instead of simply checking
    whether it
        is a null pointer.
---
 drivers/tty/serial/jsm/jsm_tty.c | 43 ++++++++------------------------
 1 file changed, 11 insertions(+), 32 deletions(-)

diff --git a/drivers/tty/serial/jsm/jsm_tty.c b/drivers/tty/serial/jsm/jsm_tty.c
index 8e42a7682c63..d42972b2d2c4 100644
--- a/drivers/tty/serial/jsm/jsm_tty.c
+++ b/drivers/tty/serial/jsm/jsm_tty.c
@@ -195,38 +195,6 @@ static int jsm_tty_open(struct uart_port *port)
 	/* Get board pointer from our array of majors we have allocated */
 	brd = channel->ch_bd;
 
-	/*
-	 * Allocate channel buffers for read/write/error.
-	 * Set flag, so we don't get trounced on.
-	 */
-	channel->ch_flags |= (CH_OPENING);
-
-	/* Drop locks, as malloc with GFP_KERNEL can sleep */
-
-	if (!channel->ch_rqueue) {
-		channel->ch_rqueue = kzalloc(RQUEUESIZE, GFP_KERNEL);
-		if (!channel->ch_rqueue) {
-			jsm_dbg(INIT, &channel->ch_bd->pci_dev,
-				"unable to allocate read queue buf\n");
-			return -ENOMEM;
-		}
-	}
-	if (!channel->ch_equeue) {
-		channel->ch_equeue = kzalloc(EQUEUESIZE, GFP_KERNEL);
-		if (!channel->ch_equeue) {
-			jsm_dbg(INIT, &channel->ch_bd->pci_dev,
-				"unable to allocate error queue buf\n");
-			return -ENOMEM;
-		}
-	}
-
-	channel->ch_flags &= ~(CH_OPENING);
-	/*
-	 * Initialize if neither terminal is open.
-	 */
-	jsm_dbg(OPEN, &channel->ch_bd->pci_dev,
-		"jsm_open: initializing channel in open...\n");
-
 	/*
 	 * Flush input queues.
 	 */
@@ -420,6 +388,17 @@ int jsm_tty_init(struct jsm_board *brd)
 		ch->ch_close_delay = 250;
 
 		init_waitqueue_head(&ch->ch_flags_wait);
+
+		if (!ch->ch_rqueue) {
+			ch->ch_rqueue = kzalloc(RQUEUESIZE, GFP_KERNEL);
+			if (!ch->ch_rqueue)
+				return -ENOMEM;
+		}
+		if (!ch->ch_equeue) {
+			ch->ch_equeue = kzalloc(EQUEUESIZE, GFP_KERNEL);
+			if (!ch->ch_equeue)
+				return -ENOMEM;
+		}
 	}
 
 	jsm_dbg(INIT, &brd->pci_dev, "finish\n");
-- 
2.17.6