Attacker Value
Unknown
(0 users assessed)
Exploitability
Unknown
(0 users assessed)
User Interaction
None
Privileges Required
Low
Attack Vector
Local
0

CVE-2021-46938

Disclosure Date: February 27, 2024 •
CVE-2021-46938 CVSS v3 Base Score: 7.8
Add MITRE ATT&CK tactics and techniques that apply to this CVE.

Description

In the Linux kernel, the following vulnerability has been resolved:

dm rq: fix double free of blk_mq_tag_set in dev remove after table load fails

When loading a device-mapper table for a request-based mapped device,
and the allocation/initialization of the blk_mq_tag_set for the device
fails, a following device remove will cause a double free.

E.g. (dmesg):
device-mapper: core: Cannot initialize queue for request-based dm-mq mapped device
device-mapper: ioctl: unable to set up device queue for new table.
Unable to handle kernel pointer dereference in virtual kernel address space
Failing address: 0305e098835de000 TEID: 0305e098835de803
Fault in home space mode while using kernel ASCE.
AS:000000025efe0007 R3:0000000000000024
Oops: 0038 ilc:3 [#1] SMP
Modules linked in: … lots of modules …
Supported: Yes, External
CPU: 0 PID: 7348 Comm: multipathd Kdump: loaded Tainted: G W X 5.3.18-53-default #1 SLE15-SP3
Hardware name: IBM 8561 T01 7I2 (LPAR)
Krnl PSW : 0704e00180000000 000000025e368eca (kfree+0x42/0x330)

         R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:2 PM:0 RI:0 EA:3

Krnl GPRS: 000000000000004a 000000025efe5230 c1773200d779968d 0000000000000000

         000000025e520270 000000025e8d1b40 0000000000000003 00000007aae10000
         000000025e5202a2 0000000000000001 c1773200d779968d 0305e098835de640
         00000007a8170000 000003ff80138650 000000025e5202a2 000003e00396faa8

Krnl Code: 000000025e368eb8: c4180041e100 lgrl %r1,25eba50b8

         000000025e368ebe: ecba06b93a55       risbg   %r11,%r10,6,185,58
        #000000025e368ec4: e3b010000008       ag      %r11,0(%r1)
        >000000025e368eca: e310b0080004       lg      %r1,8(%r11)
         000000025e368ed0: a7110001           tmll    %r1,1
         000000025e368ed4: a7740129           brc     7,25e369126
         000000025e368ed8: e320b0080004       lg      %r2,8(%r11)
         000000025e368ede: b904001b           lgr     %r1,%r11

Call Trace:
[<000000025e368eca>] kfree+0x42/0x330
[<000000025e5202a2>] blk_mq_free_tag_set+0x72/0xb8
[<000003ff801316a8>] dm_mq_cleanup_mapped_device+0x38/0x50 [dm_mod]
[<000003ff80120082>] free_dev+0x52/0xd0 [dm_mod]
[<000003ff801233f0>] __dm_destroy+0x150/0x1d0 [dm_mod]
[<000003ff8012bb9a>] dev_remove+0x162/0x1c0 [dm_mod]
[<000003ff8012a988>] ctl_ioctl+0x198/0x478 [dm_mod]
[<000003ff8012ac8a>] dm_ctl_ioctl+0x22/0x38 [dm_mod]
[<000000025e3b11ee>] ksys_ioctl+0xbe/0xe0
[<000000025e3b127a>] __s390x_sys_ioctl+0x2a/0x40
[<000000025e8c15ac>] system_call+0xd8/0x2c8
Last Breaking-Event-Address:
[<000000025e52029c>] blk_mq_free_tag_set+0x6c/0xb8
Kernel panic – not syncing: Fatal exception: panic_on_oops

When allocation/initialization of the blk_mq_tag_set fails in
dm_mq_init_request_queue(), it is uninitialized/freed, but the pointer
is not reset to NULL; so when dev_remove() later gets into
dm_mq_cleanup_mapped_device() it sees the pointer and tries to
uninitialize and free it again.

Fix this by setting the pointer to NULL in dm_mq_init_request_queue()
error-handling. Also set it to NULL in dm_mq_cleanup_mapped_device().

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CVSS V3 Severity and Metrics
Base Score:
7.8 High
Impact Score:
5.9
Exploitability Score:
1.8
Vector:
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector (AV):
Local
Attack Complexity (AC):
Low
Privileges Required (PR):
Low
User Interaction (UI):
None
Scope (S):
Unchanged
Confidentiality (C):
High
Integrity (I):
High
Availability (A):
High

General Information

Offensive Application
Unknown
Utility Class
Unknown
Ports
Unknown
OS
Unknown
Vulnerable Versions
Linux 8ae0185255ea
Linux not down converted
Prerequisites
Unknown
Discovered By
Unknown
PoC Author
Unknown
Metasploit Module
Unknown
Reporter
Unknown

Vendors

  • linux

Products

  • linux kernel
Technical Analysis