CVE-2021-46938

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> dm rq: fix double free of blk_mq_tag_set in dev remove after table load fails<br /> <br /> When loading a device-mapper table for a request-based mapped device,<br /> and the allocation/initialization of the blk_mq_tag_set for the device<br /> fails, a following device remove will cause a double free.<br /> <br /> E.g. (dmesg):<br /> device-mapper: core: Cannot initialize queue for request-based dm-mq mapped device<br /> device-mapper: ioctl: unable to set up device queue for new table.<br /> Unable to handle kernel pointer dereference in virtual kernel address space<br /> Failing address: 0305e098835de000 TEID: 0305e098835de803<br /> Fault in home space mode while using kernel ASCE.<br /> AS:000000025efe0007 R3:0000000000000024<br /> Oops: 0038 ilc:3 [#1] SMP<br /> Modules linked in: ... lots of modules ...<br /> Supported: Yes, External<br /> CPU: 0 PID: 7348 Comm: multipathd Kdump: loaded Tainted: G W X 5.3.18-53-default #1 SLE15-SP3<br /> Hardware name: IBM 8561 T01 7I2 (LPAR)<br /> Krnl PSW : 0704e00180000000 000000025e368eca (kfree+0x42/0x330)<br /> 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<br /> Krnl GPRS: 000000000000004a 000000025efe5230 c1773200d779968d 0000000000000000<br /> 000000025e520270 000000025e8d1b40 0000000000000003 00000007aae10000<br /> 000000025e5202a2 0000000000000001 c1773200d779968d 0305e098835de640<br /> 00000007a8170000 000003ff80138650 000000025e5202a2 000003e00396faa8<br /> Krnl Code: 000000025e368eb8: c4180041e100 lgrl %r1,25eba50b8<br /> 000000025e368ebe: ecba06b93a55 risbg %r11,%r10,6,185,58<br /> #000000025e368ec4: e3b010000008 ag %r11,0(%r1)<br /> &gt;000000025e368eca: e310b0080004 lg %r1,8(%r11)<br /> 000000025e368ed0: a7110001 tmll %r1,1<br /> 000000025e368ed4: a7740129 brc 7,25e369126<br /> 000000025e368ed8: e320b0080004 lg %r2,8(%r11)<br /> 000000025e368ede: b904001b lgr %r1,%r11<br /> Call Trace:<br /> [] kfree+0x42/0x330<br /> [] blk_mq_free_tag_set+0x72/0xb8<br /> [] dm_mq_cleanup_mapped_device+0x38/0x50 [dm_mod]<br /> [] free_dev+0x52/0xd0 [dm_mod]<br /> [] __dm_destroy+0x150/0x1d0 [dm_mod]<br /> [] dev_remove+0x162/0x1c0 [dm_mod]<br /> [] ctl_ioctl+0x198/0x478 [dm_mod]<br /> [] dm_ctl_ioctl+0x22/0x38 [dm_mod]<br /> [] ksys_ioctl+0xbe/0xe0<br /> [] __s390x_sys_ioctl+0x2a/0x40<br /> [] system_call+0xd8/0x2c8<br /> Last Breaking-Event-Address:<br /> [] blk_mq_free_tag_set+0x6c/0xb8<br /> Kernel panic - not syncing: Fatal exception: panic_on_oops<br /> <br /> When allocation/initialization of the blk_mq_tag_set fails in<br /> dm_mq_init_request_queue(), it is uninitialized/freed, but the pointer<br /> is not reset to NULL; so when dev_remove() later gets into<br /> dm_mq_cleanup_mapped_device() it sees the pointer and tries to<br /> uninitialize and free it again.<br /> <br /> Fix this by setting the pointer to NULL in dm_mq_init_request_queue()<br /> error-handling. Also set it to NULL in dm_mq_cleanup_mapped_device().