{"id":68258,"date":"2025-08-16T15:32:00","date_gmt":"2025-08-16T12:02:00","guid":{"rendered":"https:\/\/afaghhosting.net\/blog\/cve-2025-38517-linux-kernel-oracle-alloc_tag-semaphore-acquisition-vulnerability\/"},"modified":"2025-08-16T15:32:00","modified_gmt":"2025-08-16T12:02:00","slug":"cve-2025-38517-linux-kernel-oracle-alloc_tag-semaphore-acquisition-vulnerability","status":"publish","type":"post","link":"https:\/\/afaghhosting.net\/blog\/cve-2025-38517-linux-kernel-oracle-alloc_tag-semaphore-acquisition-vulnerability\/","title":{"rendered":"CVE-2025-38517 – Linux Kernel Oracle alloc_tag: Semaphore Acquisition Vulnerability"},"content":{"rendered":"

CVE ID : <\/strong>CVE-2025-38517
\n
\nPublished : <\/strong> Aug. 16, 2025, 11:15 a.m. | 45\u00a0minutes ago
\n
\nDescription : <\/strong>In the Linux kernel, the following vulnerability has been resolved:<\/p>\n

lib\/alloc_tag: do not acquire non-existent lock in alloc_tag_top_users()<\/p>\n

alloc_tag_top_users() attempts to lock alloc_tag_cttype->mod_lock even
\nwhen the alloc_tag_cttype is not allocated because:<\/p>\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))<\/p>\n

In all cases, alloc_tag_cttype is not allocated, and therefore
\nalloc_tag_top_users() should not attempt to acquire the semaphore.<\/p>\n

This leads to a crash on memory allocation failure by attempting to
\nacquire a non-existent semaphore:<\/p>\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 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:<\/p>\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<\/p>\n

As David Wang points out, this issue became easier to trigger after commit
\n780138b12381 (“alloc_tag: check mem_profiling_support in alloc_tag_init”).<\/p>\n

Before 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.<\/p>\n

To 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.<\/p>\n[harry.yoo@oracle.com: v3]\n
\nSeverity:<\/strong> 0.0 | NA
\n
\nVisit the link for more details, such as CVSS details, affected products, timeline, and more…<\/p>\n","protected":false},"excerpt":{"rendered":"

CVE ID : CVE-2025-38517 Published : Aug. 16, 2025, 11:15 a.m. | 45\u00a0minutes ago Description : In the Linux kernel, the following vulnerability has been resolved: lib\/alloc_tag: do not acquire non-existent lock in alloc_tag_top_users() alloc_tag_top_users() attempts to lock alloc_tag_cttype->mod_lock even when the alloc_tag_cttype is not allocated because: 1) alloc tagging is disabled because mem profiling …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"class_list":["post-68258","post","type-post","status-publish","format-standard","hentry","category-vulnerability"],"_links":{"self":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/68258","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/comments?post=68258"}],"version-history":[{"count":0,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/68258\/revisions"}],"wp:attachment":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/media?parent=68258"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/categories?post=68258"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/tags?post=68258"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}