{"cve":"CVE-2021-46938","nvd":{"published":"2024-02-27T19:04:05.823","modified":"2026-06-17T04:15:54.993","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ndm rq: fix double free of blk_mq_tag_set in dev remove after table load fails\n\nWhen loading a device-mapper table for a request-based mapped device,\nand the allocation/initialization of the blk_mq_tag_set for the device\nfails, a following device remove will cause a double free.\n\nE.g. (dmesg):\n  device-mapper: core: Cannot initialize queue for request-based dm-mq mapped device\n  device-mapper: ioctl: unable to set up device queue for new table.\n  Unable to handle kernel pointer dereference in virtual kernel address space\n  Failing address: 0305e098835de000 TEID: 0305e098835de803\n  Fault in home space mode while using kernel ASCE.\n  AS:000000025efe0007 R3:0000000000000024\n  Oops: 0038 ilc:3 [#1] SMP\n  Modules linked in: ... lots of modules ...\n  Supported: Yes, External\n  CPU: 0 PID: 7348 Comm: multipathd Kdump: loaded Tainted: G        W      X    5.3.18-53-default #1 SLE15-SP3\n  Hardware name: IBM 8561 T01 7I2 (LPAR)\n  Krnl PSW : 0704e00180000000 000000025e368eca (kfree+0x42/0x330)\n             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\n  Krnl GPRS: 000000000000004a 000000025efe5230 c1773200d779968d 0000000000000000\n             000000025e520270 000000025e8d1b40 0000000000000003 00000007aae10000\n             000000025e5202a2 0000000000000001 c1773200d779968d 0305e098835de640\n             00000007a8170000 000003ff80138650 000000025e5202a2 000003e00396faa8\n  Krnl Code: 000000025e368eb8: c4180041e100       lgrl    %r1,25eba50b8\n             000000025e368ebe: ecba06b93a55       risbg   %r11,%r10,6,185,58\n            #000000025e368ec4: e3b010000008       ag      %r11,0(%r1)\n            >000000025e368eca: e310b0080004       lg      %r1,8(%r11)\n             000000025e368ed0: a7110001           tmll    %r1,1\n             000000025e368ed4: a7740129           brc     7,25e369126\n             000000025e368ed8: e320b0080004       lg      %r2,8(%r11)\n             000000025e368ede: b904001b           lgr     %r1,%r11\n  Call Trace:\n   [<000000025e368eca>] kfree+0x42/0x330\n   [<000000025e5202a2>] blk_mq_free_tag_set+0x72/0xb8\n   [<000003ff801316a8>] dm_mq_cleanup_mapped_device+0x38/0x50 [dm_mod]\n   [<000003ff80120082>] free_dev+0x52/0xd0 [dm_mod]\n   [<000003ff801233f0>] __dm_destroy+0x150/0x1d0 [dm_mod]\n   [<000003ff8012bb9a>] dev_remove+0x162/0x1c0 [dm_mod]\n   [<000003ff8012a988>] ctl_ioctl+0x198/0x478 [dm_mod]\n   [<000003ff8012ac8a>] dm_ctl_ioctl+0x22/0x38 [dm_mod]\n   [<000000025e3b11ee>] ksys_ioctl+0xbe/0xe0\n   [<000000025e3b127a>] __s390x_sys_ioctl+0x2a/0x40\n   [<000000025e8c15ac>] system_call+0xd8/0x2c8\n  Last Breaking-Event-Address:\n   [<000000025e52029c>] blk_mq_free_tag_set+0x6c/0xb8\n  Kernel panic - not syncing: Fatal exception: panic_on_oops\n\nWhen allocation/initialization of the blk_mq_tag_set fails in\ndm_mq_init_request_queue(), it is uninitialized/freed, but the pointer\nis not reset to NULL; so when dev_remove() later gets into\ndm_mq_cleanup_mapped_device() it sees the pointer and tries to\nuninitialize and free it again.\n\nFix this by setting the pointer to NULL in dm_mq_init_request_queue()\nerror-handling. Also set it to NULL in dm_mq_cleanup_mapped_device().","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":["CWE-415"],"references":["https://git.kernel.org/stable/c/1cb02dc76f4c0a2749a02b26469512d6984252e9","https://git.kernel.org/stable/c/6086f957416a6e87236c06079fcaba7a3998aeca","https://git.kernel.org/stable/c/772b9f59657665af3b68d24d12b9d172d31f0dfb","https://git.kernel.org/stable/c/8ae0185255eaf05bd66f4215c81e99bf01140fd9","https://git.kernel.org/stable/c/8e947c8f4a5620df77e43c9c75310dc510250166"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:45:59.823092188+00:00"},"epss":{"cve":"CVE-2021-46938","score":0.00248,"percentile":0.16151,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}