CVE-2026-98515 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/nouveau: fix double-free in nvif_vmm_dtor
On failure, nouveau_cli_init() calls nouveau_cli_fini() to tear the client down. Then, nouveau_drm_open() also enters into its cleanup path and calls nouveau_cli_fini() AGAIN. nouveau_cli_fini() calls nouveau_vmm_fini():
void nouveau_vmm_fini(struct nouveau_vmm *vmm) {
nouveau_svmm_fini(&vmm->svmm); nvif_vmm_dtor(&vmm->vmm); vmm->cli = NULL; }
Inside nvif_vmm_dtor(), vmm->page is freed unconditionally:
void nvif_vmm_dtor(struct nvif_vmm *vmm) {
kfree(vmm->page); nvif_object_dtor(&vmm->object); }
vmm->page is never cleared after being freed, so the second call of nvif_vmm_dtor() will cause a double-free.
Found by fuzzing the nouveau driver with a modified Syzkaller:
BUG: KASAN: double-free in nvif_vmm_dtor+0x31/0x50 drivers/gpu/drm/nouveau/nvif/vmm.c:194 Free of addr ffff888010fcdc30 by task syz.0.173/2567
CPU: 1 UID: 0 PID: 2567 Comm: syz.0.173 Not tainted 7.2.0 #24 PREEMPT(lazy) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x95/0xe0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline]
print_report+0xcb/0x5a0 mm/kasan/report.c:482 kasan_report_invalid_free+0xaa/0xd0 mm/kasan/report.c:557 check_slab_allocation+0xe4/0x110 mm/kasan/common.c:235 kasan_slab_pre_free include/linux/kasan.h:199 [inline]
slab_free_hook mm/slub.c:2622 [inline]
slab_free mm/slub.c:6377 [inline]
kfree+0x192/0x590 mm/slub.c:6692 nvif_vmm_dtor+0x31/0x50 drivers/gpu/drm/nouveau/nvif/vmm.c:194 nouveau_vmm_fini+0x16/0x50 drivers/gpu/drm/nouveau/nouveau_vmm.c:127 nouveau_cli_fini+0x10e/0x210 drivers/gpu/drm/nouveau/nouveau_drm.c:225 nouveau_drm_open+0x24e/0x740 drivers/gpu/drm/nouveau/nouveau_drm.c:1255 drm_file_alloc+0x5f2/0xad0 drivers/gpu/drm/drm_file.c:176 drm_open_helper+0x1d7/0x4a0 drivers/gpu/drm/drm_file.c:335 drm_open+0x190/0x3d0 drivers/gpu/drm/drm_file.c:388 drm_stub_open+0x1f2/0x460 drivers/gpu/drm/drm_drv.c:1211 chrdev_open+0x21c/0x660 fs/char_dev.c:411 do_dentry_open+0x59d/0x12b0 fs/open.c:947 vfs_open+0x82/0x390 fs/open.c:1052 do_open fs/namei.c:4700 [inline]
path_openat+0x2345/0x3420 fs/namei.c:4863 do_file_open+0x207/0x460 fs/namei.c:4892 do_sys_openat2+0xd1/0x1d0 fs/open.c:1368 do_sys_open fs/open.c:1374 [inline]
__do_sys_openat fs/open.c:1390 [inline]
__se_sys_openat fs/open.c:1385 [inline]
__x64_sys_openat+0x144/0x200 fs/open.c:1385 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x690 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fc6d687594d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fc6d5295008 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007fc6d6b06180 RCX: 00007fc6d687594d RDX: 0000000000022501 RSI: 0000200000000000 RDI: ffffffffffffff9c RBP: 00007fc6d691c303 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fc6d6b06218 R14: 00007fc6d6b06180 R15: 00007ffd9451d760 </TASK>
Allocated by task 2567 on cpu 1 at 163.593900s: kasan_save_stack+0x24/0x50 mm/kasan/common.c:57 kasan_save_track+0x17/0x60 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline]
__do_kmalloc_node mm/slub.c:5334 [inline]
__kmalloc_noprof+0x304/0x7c0 mm/slub.c:5359 _kmalloc_noprof include/linux/slab.h:992 [inline]
nvif_vmm_ctor+0x3c0/0x7e0 drivers/gpu/drm/nouveau/nvif/vmm.c:237 nouveau_vmm_init+0x40/0x90 drivers/gpu/drm/nouveau/nouveau_vmm.c:134 nouveau_cli_init+0x7b9/0 ---truncated---
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Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel's Nouveau driver, which provides open-source graphics support for NVIDIA GPUs, contains a critical memory management flaw identified as CVE-2024-something (specifically related to the nvif_vmm_dtor function). This vulnerability manifests as a double-free condition during the initialization and cleanup sequences of the DRM client interface. The issue arises from an inconsistent error handling path where resources are deallocated multiple times without proper state tracking or pointer invalidation, leading to potential kernel instability and security risks.
The technical root cause lies in the interaction between nouveau_cli_init, nouveau_cli_fini, and nouveau_drm_open functions within drivers/gpu/drm/nouveau/. When nouveau_cli_init fails during its setup phase, it correctly invokes nouveau_cli_fini to tear down any partially initialized client structures. However, if this failure occurs while a file descriptor is being opened via nouveau_drm_open, the open function also enters its own error handling path. This secondary cleanup routine subsequently calls nouveau_cli_fini again for the same client instance. Inside nouveau_cli_fini, the function nouveau_vmm_fini is invoked to release video memory management resources. Within nouveau_vmm_fini, the nvif_vmm_dtor function is called to destroy the virtual memory manager object.
The specific flaw exists within nvif_vmm_dtor, which unconditionally calls kfree on vmm->page without checking if it has already been freed or clearing the pointer afterward. Because the first call from nouveau_cli_fini frees this memory but leaves the vmm->pointer pointing to the now-deallocated address, the second invocation of nvif_vmm_dtor during the subsequent cleanup phase attempts to free the same memory block again. This results in a double-free vulnerability, which is detected by Kernel Address Sanitizer (KASAN) as an invalid slab allocation error. The lack of nullification after freeing allows the kernel's memory allocator to interpret the stale pointer as valid for another deallocation attempt, corrupting internal heap metadata structures.
From a security perspective, this double-free condition maps directly to CWE-415: Double Free, which is classified under CWE-787: Out-of-bounds Write in many contexts due to potential memory corruption side effects. In the MITRE ATT&CK framework for Enterprise, this vulnerability aligns with Tactic TA0004 (Privilege Escalation) and Technique T1068: Exploitation for Privilege Escalation. An attacker who can trigger this code path through local user-space interactions may corrupt kernel memory structures such as slab caches or heap metadata. Such corruption can potentially be leveraged to achieve arbitrary read/write primitives, leading to full system compromise or denial of service by crashing the kernel via a panic condition triggered by invalid free operations.
The operational impact includes severe stability issues for systems running affected versions of the Linux kernel with Nouveau driver support. Local users with access to GPU devices could trigger this vulnerability by opening and closing device nodes under specific error conditions during initialization. The resulting memory corruption can lead to system crashes, data loss, or exploitation vectors that bypass standard security controls due to the high privilege level at which the double-free occurs within the kernel space.
Mitigation strategies primarily involve applying upstream Linux kernel patches that address this specific race condition in the Nouveau driver codebase. Developers should ensure that vmm->page is set to NULL immediately after kfree is called in nvif_vmm_dtor, ensuring subsequent calls are no-ops or safely handled. Additionally, reviewing error handling paths in nouveau_cli_init and nouveau_drm_open to prevent redundant cleanup calls for the same client instance would resolve the logical flaw. System administrators should update their kernels to versions where this patch has been merged and released, particularly those targeting stable branches containing fixes for DRM subsystem memory management issues.