CVE-2025-40009
Full vulnerability record from the local CVENow database.
Description
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 <snip registers, unreliable trace> [ 44.946828] Call Trace: [ 44.947030] <TASK> [ 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.
View original CVE JSON
{
"id": "CVE-2025-40009",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-10-20T16:15:37.593",
"lastModified": "2026-10-19T21:10:00.160",
"vulnStatus": "Deferred",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/proc/task_mmu: check p->vec_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<snip registers, unreliable trace>\n\n[ 44.946828] Call Trace:\n[ 44.947030] <TASK>\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->vec_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->vec_buf_index.\n\nFix it by explicitly checking p->vec_buf for NULL before dereferencing.\n\nOther sites that might run into same deref-issue are already (directly or\ntransitively) protected by checking p->vec_buf.\n\nNote:\nFrom PAGEMAP_SCAN man page, it seems vec_len = 0 is valid when no output\nis requested and it's only the side effects caller is interested in,\nhence it passes check in pagemap_scan_get_args().\n\nThis issue was found by syzkaller."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nfs/proc/task_mmu: verificar p->vec_buf en busca de NULL\n\nCuando el ioctl PAGEMAP_SCAN se invoca con vec_len = 0 y llega a pagemap_scan_backout_range(), el kernel entra en pánico con 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<snip registers, unreliable trace>\n\n[ 44.946828] Call Trace:\n[ 44.947030] <TASK>\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 en pagemap_scan_init_bounce_buffer() significa que no se asignan búferes y p->vec_buf permanece establecido en NULL.\n\nEsto rompe una suposición hecha más tarde en pagemap_scan_backout_range(), de que page_region siempre se asigna para p->vec_buf_index.\n\nSolucionarlo verificando explícitamente p->vec_buf en busca de NULL antes de desreferenciar.\n\nOtros sitios que podrían encontrarse con el mismo problema de desreferencia ya están protegidos (directa o transitivamente) al verificar p->vec_buf.\n\nNota:\nSegún la página man de PAGEMAP_SCAN, parece que vec_len = 0 es válido cuando no se solicita ninguna salida y el llamador solo está interesado en los efectos secundarios, por lo tanto, pasa la verificación en pagemap_scan_get_args().\n\nEste problema fue encontrado por syzkaller."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"fs/proc/task_mmu.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "52526ca7fdb905a768a93f8faa418e9b988fc34b",
"lessThan": "ca988dcdc6683ecd9de5f525ce469588a9141c21",
"versionType": "git",
"status": "affected"
},
{
"version": "52526ca7fdb905a768a93f8faa418e9b988fc34b",
"lessThan": "a2cb8818a3d915cd33a1e8b2babc1bb0c34862c3",
"versionType": "git",
"status": "affected"
},
{
"version": "52526ca7fdb905a768a93f8faa418e9b988fc34b",
"lessThan": "28aa29986dde79e8466bc87569141291053833f5",
"versionType": "git",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"fs/proc/task_mmu.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "6.7",
"status": "affected"
},
{
"version": "0",
"lessThan": "6.7",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.50",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.16.10",
"lessThanOrEqual": "6.16.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.17",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {},
"references": [
{
"url": "https://git.kernel.org/stable/c/28aa29986dde79e8466bc87569141291053833f5",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/a2cb8818a3d915cd33a1e8b2babc1bb0c34862c3",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/ca988dcdc6683ecd9de5f525ce469588a9141c21",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}