{"cve":"CVE-2025-38517","nvd":{"published":"2025-08-16T11:15:44.897","modified":"2026-06-17T09:17:01.753","status":"Analyzed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nlib/alloc_tag: do not acquire non-existent lock in alloc_tag_top_users()\n\nalloc_tag_top_users() attempts to lock alloc_tag_cttype->mod_lock even\nwhen the alloc_tag_cttype is not allocated because:\n\n  1) alloc tagging is disabled because mem profiling is disabled\n     (!alloc_tag_cttype)\n  2) alloc tagging is enabled, but not yet initialized (!alloc_tag_cttype)\n  3) alloc tagging is enabled, but failed initialization\n     (!alloc_tag_cttype or IS_ERR(alloc_tag_cttype))\n\nIn all cases, alloc_tag_cttype is not allocated, and therefore\nalloc_tag_top_users() should not attempt to acquire the semaphore.\n\nThis leads to a crash on memory allocation failure by attempting to\nacquire a non-existent semaphore:\n\n  Oops: general protection fault, probably for non-canonical address 0xdffffc000000001b: 0000 [#3] SMP KASAN NOPTI\n  KASAN: null-ptr-deref in range [0x00000000000000d8-0x00000000000000df]\n  CPU: 2 UID: 0 PID: 1 Comm: systemd Tainted: G      D             6.16.0-rc2 #1 VOLUNTARY\n  Tainted: [D]=DIE\n  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014\n  RIP: 0010:down_read_trylock+0xaa/0x3b0\n  Code: d0 7c 08 84 d2 0f 85 a0 02 00 00 8b 0d df 31 dd 04 85 c9 75 29 48 b8 00 00 00 00 00 fc ff df 48 8d 6b 68 48 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 88 02 00 00 48 3b 5b 68 0f 85 53 01 00 00 65 ff\n  RSP: 0000:ffff8881002ce9b8 EFLAGS: 00010016\n  RAX: dffffc0000000000 RBX: 0000000000000070 RCX: 0000000000000000\n  RDX: 000000000000001b RSI: 000000000000000a RDI: 0000000000000070\n  RBP: 00000000000000d8 R08: 0000000000000001 R09: ffffed107dde49d1\n  R10: ffff8883eef24e8b R11: ffff8881002cec20 R12: 1ffff11020059d37\n  R13: 00000000003fff7b R14: ffff8881002cec20 R15: dffffc0000000000\n  FS:  00007f963f21d940(0000) GS:ffff888458ca6000(0000) knlGS:0000000000000000\n  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n  CR2: 00007f963f5edf71 CR3: 000000010672c000 CR4: 0000000000350ef0\n  Call Trace:\n   <TASK>\n   codetag_trylock_module_list+0xd/0x20\n   alloc_tag_top_users+0x369/0x4b0\n   __show_mem+0x1cd/0x6e0\n   warn_alloc+0x2b1/0x390\n   __alloc_frozen_pages_noprof+0x12b9/0x21a0\n   alloc_pages_mpol+0x135/0x3e0\n   alloc_slab_page+0x82/0xe0\n   new_slab+0x212/0x240\n   ___slab_alloc+0x82a/0xe00\n   </TASK>\n\nAs David Wang points out, this issue became easier to trigger after commit\n780138b12381 (\"alloc_tag: check mem_profiling_support in alloc_tag_init\").\n\nBefore the commit, the issue occurred only when it failed to allocate and\ninitialize alloc_tag_cttype or if a memory allocation fails before\nalloc_tag_init() is called.  After the commit, it can be easily triggered\nwhen memory profiling is compiled but disabled at boot.\n\nTo properly determine whether alloc_tag_init() has been called and its\ndata structures initialized, verify that alloc_tag_cttype is a valid\npointer before acquiring the semaphore.  If the variable is NULL or an\nerror value, it has not been properly initialized.  In such a case, just\nskip and do not attempt to acquire the semaphore.\n\n[harry.yoo@oracle.com: v3]","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":["CWE-476"],"references":["https://git.kernel.org/stable/c/22bf79c0c2301b6e15a688220284b147774d277e","https://git.kernel.org/stable/c/99af22cd34688cc0d535a1919e0bea4cbc6c1ea1","https://git.kernel.org/stable/c/febc0b5dbabda414565bdfaaaa59d26f787d5fe7"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:06:45.861874017+00:00"},"epss":{"cve":"CVE-2025-38517","score":0.00152,"percentile":0.0437,"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."]}