ghsa-864c-jv4g-gp7q
Vulnerability from github
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 is disabled (!alloc_tag_cttype) 2) alloc tagging is enabled, but not yet initialized (!alloc_tag_cttype) 3) alloc tagging is enabled, but failed initialization (!alloc_tag_cttype or IS_ERR(alloc_tag_cttype))
In all cases, alloc_tag_cttype is not allocated, and therefore alloc_tag_top_users() should not attempt to acquire the semaphore.
This leads to a crash on memory allocation failure by attempting to acquire a non-existent semaphore:
Oops: general protection fault, probably for non-canonical address 0xdffffc000000001b: 0000 [#3] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x00000000000000d8-0x00000000000000df] CPU: 2 UID: 0 PID: 1 Comm: systemd Tainted: G D 6.16.0-rc2 #1 VOLUNTARY Tainted: [D]=DIE Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:down_read_trylock+0xaa/0x3b0 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 RSP: 0000:ffff8881002ce9b8 EFLAGS: 00010016 RAX: dffffc0000000000 RBX: 0000000000000070 RCX: 0000000000000000 RDX: 000000000000001b RSI: 000000000000000a RDI: 0000000000000070 RBP: 00000000000000d8 R08: 0000000000000001 R09: ffffed107dde49d1 R10: ffff8883eef24e8b R11: ffff8881002cec20 R12: 1ffff11020059d37 R13: 00000000003fff7b R14: ffff8881002cec20 R15: dffffc0000000000 FS: 00007f963f21d940(0000) GS:ffff888458ca6000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f963f5edf71 CR3: 000000010672c000 CR4: 0000000000350ef0 Call Trace: codetag_trylock_module_list+0xd/0x20 alloc_tag_top_users+0x369/0x4b0 __show_mem+0x1cd/0x6e0 warn_alloc+0x2b1/0x390 __alloc_frozen_pages_noprof+0x12b9/0x21a0 alloc_pages_mpol+0x135/0x3e0 alloc_slab_page+0x82/0xe0 new_slab+0x212/0x240 ___slab_alloc+0x82a/0xe00
As David Wang points out, this issue became easier to trigger after commit 780138b12381 ("alloc_tag: check mem_profiling_support in alloc_tag_init").
Before the commit, the issue occurred only when it failed to allocate and initialize alloc_tag_cttype or if a memory allocation fails before alloc_tag_init() is called. After the commit, it can be easily triggered when memory profiling is compiled but disabled at boot.
To properly determine whether alloc_tag_init() has been called and its data structures initialized, verify that alloc_tag_cttype is a valid pointer before acquiring the semaphore. If the variable is NULL or an error value, it has not been properly initialized. In such a case, just skip and do not attempt to acquire the semaphore.
[harry.yoo@oracle.com: v3]
{
"affected": [],
"aliases": [
"CVE-2025-38517"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-08-16T11:15:44Z",
"severity": null
},
"details": "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-\u003emod_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 \u003c80\u003e 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 \u003cTASK\u003e\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 \u003c/TASK\u003e\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]",
"id": "GHSA-864c-jv4g-gp7q",
"modified": "2025-08-16T12:30:32Z",
"published": "2025-08-16T12:30:32Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38517"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/22bf79c0c2301b6e15a688220284b147774d277e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/99af22cd34688cc0d535a1919e0bea4cbc6c1ea1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/febc0b5dbabda414565bdfaaaa59d26f787d5fe7"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
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