ghsa-cmvf-g3gj-cgc9
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
fs/proc/task_mmu: check p->vec_buf for NULL
When the PAGEMAP_SCAN ioctl is invoked with vec_len = 0 reaches pagemap_scan_backout_range(), kernel panics with null-ptr-deref:
[ 44.936808] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI [ 44.937797] KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] [ 44.938391] CPU: 1 UID: 0 PID: 2480 Comm: reproducer Not tainted 6.17.0-rc6 #22 PREEMPT(none) [ 44.939062] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 44.939935] RIP: 0010:pagemap_scan_thp_entry.isra.0+0x741/0xa80
[ 44.946828] Call Trace: [ 44.947030] [ 44.949219] pagemap_scan_pmd_entry+0xec/0xfa0 [ 44.952593] walk_pmd_range.isra.0+0x302/0x910 [ 44.954069] walk_pud_range.isra.0+0x419/0x790 [ 44.954427] walk_p4d_range+0x41e/0x620 [ 44.954743] walk_pgd_range+0x31e/0x630 [ 44.955057] __walk_page_range+0x160/0x670 [ 44.956883] walk_page_range_mm+0x408/0x980 [ 44.958677] walk_page_range+0x66/0x90 [ 44.958984] do_pagemap_scan+0x28d/0x9c0 [ 44.961833] do_pagemap_cmd+0x59/0x80 [ 44.962484] __x64_sys_ioctl+0x18d/0x210 [ 44.962804] do_syscall_64+0x5b/0x290 [ 44.963111] entry_SYSCALL_64_after_hwframe+0x76/0x7e
vec_len = 0 in pagemap_scan_init_bounce_buffer() means no buffers are allocated and p->vec_buf remains set to NULL.
This breaks an assumption made later in pagemap_scan_backout_range(), that page_region is always allocated for p->vec_buf_index.
Fix it by explicitly checking p->vec_buf for NULL before dereferencing.
Other sites that might run into same deref-issue are already (directly or transitively) protected by checking p->vec_buf.
Note: From PAGEMAP_SCAN man page, it seems vec_len = 0 is valid when no output is requested and it's only the side effects caller is interested in, hence it passes check in pagemap_scan_get_args().
This issue was found by syzkaller.
{
"affected": [],
"aliases": [
"CVE-2025-40009"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-10-20T16:15:37Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/proc/task_mmu: check p-\u003evec_buf for NULL\n\nWhen the PAGEMAP_SCAN ioctl is invoked with vec_len = 0 reaches\npagemap_scan_backout_range(), kernel panics with null-ptr-deref:\n\n[ 44.936808] Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN NOPTI\n[ 44.937797] KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]\n[ 44.938391] CPU: 1 UID: 0 PID: 2480 Comm: reproducer Not tainted 6.17.0-rc6 #22 PREEMPT(none)\n[ 44.939062] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014\n[ 44.939935] RIP: 0010:pagemap_scan_thp_entry.isra.0+0x741/0xa80\n\n\u003csnip registers, unreliable trace\u003e\n\n[ 44.946828] Call Trace:\n[ 44.947030] \u003cTASK\u003e\n[ 44.949219] pagemap_scan_pmd_entry+0xec/0xfa0\n[ 44.952593] walk_pmd_range.isra.0+0x302/0x910\n[ 44.954069] walk_pud_range.isra.0+0x419/0x790\n[ 44.954427] walk_p4d_range+0x41e/0x620\n[ 44.954743] walk_pgd_range+0x31e/0x630\n[ 44.955057] __walk_page_range+0x160/0x670\n[ 44.956883] walk_page_range_mm+0x408/0x980\n[ 44.958677] walk_page_range+0x66/0x90\n[ 44.958984] do_pagemap_scan+0x28d/0x9c0\n[ 44.961833] do_pagemap_cmd+0x59/0x80\n[ 44.962484] __x64_sys_ioctl+0x18d/0x210\n[ 44.962804] do_syscall_64+0x5b/0x290\n[ 44.963111] entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nvec_len = 0 in pagemap_scan_init_bounce_buffer() means no buffers are\nallocated and p-\u003evec_buf remains set to NULL.\n\nThis breaks an assumption made later in pagemap_scan_backout_range(), that\npage_region is always allocated for p-\u003evec_buf_index.\n\nFix it by explicitly checking p-\u003evec_buf for NULL before dereferencing.\n\nOther sites that might run into same deref-issue are already (directly or\ntransitively) protected by checking p-\u003evec_buf.\n\nNote:\nFrom PAGEMAP_SCAN man page, it seems vec_len = 0 is valid when no output\nis requested and it\u0027s only the side effects caller is interested in,\nhence it passes check in pagemap_scan_get_args().\n\nThis issue was found by syzkaller.",
"id": "GHSA-cmvf-g3gj-cgc9",
"modified": "2025-10-20T18:30:33Z",
"published": "2025-10-20T18:30:33Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-40009"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/28aa29986dde79e8466bc87569141291053833f5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a2cb8818a3d915cd33a1e8b2babc1bb0c34862c3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ca988dcdc6683ecd9de5f525ce469588a9141c21"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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