CVE-2019-15923: NULL Pointer Dereference (CWE-476)
value: An issue was discovered in the Linux kernel before 5.0.9. There is a NULL pointer dereference for a cd data structure if alloc_disk fails in drivers/block/paride/pf.c.
CWE description: The product dereferences a pointer that it expects to be valid but is NULL.
CVSS v3 base score: 5.5
Published: 2019-09-04T19:15Z
Repository: https://github.com/torvalds/linux
Language: C
Files changed: drivers/block/paride/pcd.c
Commit date: 2019-04-05 09:24:34 -0600
Commit message: paride/pcd: Fix potential NULL pointer dereference and mem leak

Syzkaller report this:

pcd: pcd version 1.07, major 46, nice 0
pcd0: Autoprobe failed
pcd: No CD-ROM drive found
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN PTI
CPU: 1 PID: 4525 Comm: syz-executor.0 Not tainted 5.1.0-rc3+ #8
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
RIP: 0010:pcd_init+0x95c/0x1000 [pcd]
Code: c4 ab f7 48 89 d8 48 c1 e8 03 80 3c 28 00 74 08 48 89 df e8 56 a3 da f7 4c 8b 23 49 8d bc 24 80 05 00 00 48 89 f8 48 c1 e8 03 <80> 3c 28 00 74 05 e8 39 a3 da f7 49 8b bc 24 80 05 00 00 e8 cc b2
RSP: 0018:ffff8881e84df880 EFLAGS: 00010202
RAX: 00000000000000b0 RBX: ffffffffc155a088 RCX: ffffffffc1508935
RDX: 0000000000040000 RSI: ffffc900014f0000 RDI: 0000000000000580
RBP: dffffc0000000000 R08: ffffed103ee658b8 R09: ffffed103ee658b8
R10: 0000000000000001 R11: ffffed103ee658b7 R12: 0000000000000000
R13: ffffffffc155a778 R14: ffffffffc155a4a8 R15: 0000000000000003
FS:  00007fe71bee3700(0000) GS:ffff8881f7300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055a7334441a8 CR3: 00000001e9674003 CR4: 00000000007606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 ? 0xffffffffc1508000
 ? 0xffffffffc1508000
 do_one_initcall+0xbc/0x47d init/main.c:901
 do_init_module+0x1b5/0x547 kernel/module.c:3456
 load_module+0x6405/0x8c10 kernel/module.c:3804
 __do_sys_finit_module+0x162/0x190 kernel/module.c:3898
 do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x462e99
Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe71bee2c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
RAX: ffffffffffffffda RBX: 000000000073bf00 RCX: 0000000000462e99
RDX: 0000000000000000 RSI: 0000000020000180 RDI: 0000000000000003
RBP: 00007fe71bee2c70 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe71bee36bc
R13: 00000000004bcefa R14: 00000000006f6fb0 R15: 0000000000000004
Modules linked in: pcd(+) paride solos_pci atm ts_fsm rtc_mt6397 mac80211 nhc_mobility nhc_udp nhc_ipv6 nhc_hop nhc_dest nhc_fragment nhc_routing 6lowpan rtc_cros_ec memconsole intel_xhci_usb_role_switch roles rtc_wm8350 usbcore industrialio_triggered_buffer kfifo_buf industrialio asc7621 dm_era dm_persistent_data dm_bufio dm_mod tpm gnss_ubx gnss_serial serdev gnss max2165 cpufreq_dt hid_penmount hid menf21bmc_wdt rc_core n_tracesink ide_gd_mod cdns_csi2tx v4l2_fwnode videodev media pinctrl_lewisburg pinctrl_intel iptable_security iptable_raw iptable_mangle iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 iptable_filter bpfilter ip6_vti ip_vti ip_gre ipip sit tunnel4 ip_tunnel hsr veth netdevsim vxcan batman_adv cfg80211 rfkill chnl_net caif nlmon dummy team bonding vcan bridge stp llc ip6_gre gre ip6_tunnel tunnel6 tun joydev mousedev ppdev kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel aesni_intel aes_x86_64 crypto_simd
 ide_pci_generic piix input_leds cryptd glue_helper psmouse ide_core intel_agp serio_raw intel_gtt ata_generic i2c_piix4 agpgart pata_acpi parport_pc parport floppy rtc_cmos sch_fq_codel ip_tables x_tables sha1_ssse3 sha1_generic ipv6 [last unloaded: bmc150_magn]
Dumping ftrace buffer:
   (ftrace buffer empty)
---[ end trace d873691c3cd69f56 ]---

If alloc_disk fails in pcd_init_units, cd->disk will be
NULL, however in pcd_detect and pcd_exit, it's not check
this before free.It may result a NULL pointer dereference.

Also when register_blkdev failed, blk_cleanup_queue() and
blk_mq_free_tag_set() should be called to free resources.

Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 81b74ac68c28 ("paride/pcd: cleanup queues when detection fails")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Diff: diff --git a/drivers/block/paride/pcd.c b/drivers/block/paride/pcd.c
index 377a694dc228..6d415b20fb70 100644
--- a/drivers/block/paride/pcd.c
+++ b/drivers/block/paride/pcd.c
@@ -312,10 +312,11 @@ static void pcd_init_units(void)
 			continue;
 
 		disk->queue = blk_mq_init_sq_queue(&cd->tag_set, &pcd_mq_ops,
 						   1, BLK_MQ_F_SHOULD_MERGE);
 		if (IS_ERR(disk->queue)) {
+			put_disk(disk);
 			disk->queue = NULL;
 			continue;
 		}
 
 		INIT_LIST_HEAD(&cd->rq_list);
@@ -748,10 +749,12 @@ static int pcd_detect(void)
 	if (k)
 		return 0;
 
 	printk("%s: No CD-ROM drive found\n", name);
 	for (unit = 0, cd = pcd; unit < PCD_UNITS; unit++, cd++) {
+		if (!cd->disk)
+			continue;
 		blk_cleanup_queue(cd->disk->queue);
 		cd->disk->queue = NULL;
 		blk_mq_free_tag_set(&cd->tag_set);
 		put_disk(cd->disk);
 	}
@@ -1008,12 +1011,18 @@ static int __init pcd_init(void)
 
 	/* get the atapi capabilities page */
 	pcd_probe_capabilities();
 
 	if (register_blkdev(major, name)) {
-		for (unit = 0, cd = pcd; unit < PCD_UNITS; unit++, cd++)
+		for (unit = 0, cd = pcd; unit < PCD_UNITS; unit++, cd++) {
+			if (!cd->disk)
+				continue;
+
+			blk_cleanup_queue(cd->disk->queue);
+			blk_mq_free_tag_set(&cd->tag_set);
 			put_disk(cd->disk);
+		}
 		return -EBUSY;
 	}
 
 	for (unit = 0, cd = pcd; unit < PCD_UNITS; unit++, cd++) {
 		if (cd->present) {
@@ -1030,10 +1039,13 @@ static void __exit pcd_exit(void)
 {
 	struct pcd_unit *cd;
 	int unit;
 
 	for (unit = 0, cd = pcd; unit < PCD_UNITS; unit++, cd++) {
+		if (!cd->disk)
+			continue;
+
 		if (cd->present) {
 			del_gendisk(cd->disk);
 			pi_release(cd->pi);
 			unregister_cdrom(&cd->info);
 		}

Vulnerable code: 		for (unit = 0, cd = pcd; unit < PCD_UNITS; unit++, cd++)
Fixed code: 			put_disk(disk);
		if (!cd->disk)
			continue;
		for (unit = 0, cd = pcd; unit < PCD_UNITS; unit++, cd++) {
			if (!cd->disk)
				continue;

			blk_cleanup_queue(cd->disk->queue);
			blk_mq_free_tag_set(&cd->tag_set);
		}
		if (!cd->disk)
			continue;