CVE-2025-40009

Description

In the Linux kernel, the following vulnerability has been resolved:fs/proc/task_mmu: check p->vec_buf for nullWhen the PAGEMAP_SCAN ioctl is invoked with vec_len = 0 reachespagemap_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+0x76/0x7evec_len = 0 in pagemap_scan_init_bounce_buffer() means no buffers areallocated and p->vec_buf remains set to null.This breaks an assumption made later in pagemap_scan_backout_range(), thatpage_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 ortransitively) protected by checking p->vec_buf.Note:From PAGEMAP_SCAN man page, it seems vec_len = 0 is valid when no outputis requested and its only the side effects caller is interested in,hence it passes check in pagemap_scan_get_args().This issue was found by syzkaller.

Risk Information

Associated Vulnerability

Patch Details

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234