CVE-2026-64582: RDMA/rxe: Fix a use-after-free problem in rxe_mmap

From: Greg Kroah-Hartman <[email protected]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

RDMA/rxe: Fix a use-after-free problem in rxe_mmap

rxe_mmap() removes a rxe_mmap_info struct from the pending_mmaps list
and releases pending_lock while the struct's kref is still at 1:

   list_del_init(&ip->pending_mmaps);
   spin_unlock_bh(&rxe->pending_lock);   /* ref == 1, no lock held */
   ret = remap_vmalloc_range(vma, ip->obj, 0);  /* walks PTEs */
   [...]
   rxe_vma_open(vma);                    /* kref_get, ref → 2 */
   remap_vmalloc_range_partial() walks PTEs without any lock.

A concurrent DESTROY_CQ ioctl on another CPU calls:

    kref_put(&q->ip->ref, rxe_mmap_release)   /* ref 1→0 */
    vfree(ip->obj)   /* clears vmalloc PTEs mid-walk */
    kfree(ip)        /* frees rxe_mmap_info */

This yields:

   1. Kernel crash, vmalloc_to_page() returns NULL when vfree wins the
   per-PTE race -> vm_insert_page(NULL) → GPF in validate_page_before_insert

   2. Page UAF, vmalloc_to_page() reads a stale PTE before vfree clears
   it. User VMA holds a PTE to a free'd page which might eventually get
   reallocated later by vmalloc which allows the attacker to get a clean
   page-level UAF.

   It is worth noting that even though a page-level UAF is possible given
   the strong primitive, it is statistically very difficult to achieve
   given the very short time window (after the last insert_page and before
   the kref_get).

The call trace are as below:

  Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN NOPTI
  KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
  CPU: 0 UID: 1000 PID: 413 Comm: poc Not tainted 7.0.0-rc5-dirty #28 PREEMPT(lazy)
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
  RIP: 0010:validate_page_before_insert+0x32/0x300
  Code: e5 41 57 41 56 49 89 fe 41 55 41 54 53 48 89 f3 e8 93 b5 a3 ff 48 8d 7b 08 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 7b 02 00 00 4c 8b 63 08 31 ff 4d 89 e5 41 83 e5
  RSP: 0018:ffff88811b15f2f0 EFLAGS: 00000202
  RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000008
  RBP: ffff88811b15f318 R08: 0000000000000000 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000000000 R12: ffff8881181eee00
  R13: 0000000000000000 R14: ffff8881181eee00 R15: ffff8881181eee20
  FS:  00007b1e000f76c0(0000) GS:ffff8884268e0000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007b1e00a24ac0 CR3: 0000000116eb3000 CR4: 00000000000006f0
  Call Trace:
   <TASK>
   insert_page+0x8f/0x190
   ? __pfx_insert_page+0x10/0x10
   ? kasan_save_alloc_info+0x38/0x60
   vm_insert_page+0x2e7/0x400
   remap_vmalloc_range_partial+0x212/0x3e0
   remap_vmalloc_range+0x6e/0xb0
   ? __kasan_check_write+0x14/0x30
   rxe_mmap+0x2e9/0x5d0
   ib_uverbs_mmap+0x1ad/0x2c0
   __mmap_region+0x12c2/0x2ad0
   ? __pfx___mmap_region+0x10/0x10
   ? __sanitizer_cov_trace_switch+0x58/0xb0
   ? mas_prev_slot+0x360/0x39c0
   ? __sanitizer_cov_trace_switch+0x58/0xb0
   ? mas_next_slot+0x1e5b/0x2f40
   ? __sanitizer_cov_trace_cmp8+0x18/0x30
   ? unmapped_area_topdown+0x4dd/0x610
   ? kfree+0x1b1/0x440
   ? free_cpumask_var+0x16/0x30
   ? __kasan_slab_free+0x7d/0xa0
   ? __sanitizer_cov_trace_cmp8+0x18/0x30
   mmap_region+0x2e6/0x3c0
   do_mmap+0xa3e/0x12a0
   ? __pfx_do_mmap+0x10/0x10
   ? __kasan_check_write+0x14/0x30
   ? down_write_killable+0xba/0x160
   ? __pfx_down_write_killable+0x10/0x10
   ? __sanitizer_cov_trace_cmp4+0x16/0x30
   vm_mmap_pgoff+0x2d4/0x4a0
   ? __pfx_vm_mmap_pgoff+0x10/0x10
   ? fget+0x1bf/0x270
   ksys_mmap_pgoff+0x40c/0x690
   ? __sanitizer_cov_trace_const_cmp4+0x16/0x30
   ? __pfx_ksys_mmap_pgoff+0x10/0x10
   ? __kasan_check_write+0x14/0x30
   ? _raw_spin_trylock+0xbb/0x130
   ? __pfx__raw_spin_trylock+0x10/0x10
   __x64_sys_mmap+0x135/0x1e0
   x64_sys_call+0x1c14/0x2790
   do_syscall_64+0xd2/0x1050
   ? rcu_core+0x352/0x7d0
   ? rcu_core_si+0xe/0x20
   ? handle_softirqs+0x1aa/0x650
   ? __sanitizer_cov_trace_cmp4+0x16/0x30
   ? fpregs_assert_state_consistent+0xe1/0x160
   ? irqentry_exit+0xb1/0x670
   entry_SYSCALL_64_after_hwframe+0x76/0x7e

The Linux kernel CVE team has assigned CVE-2026-64582 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 6.6.145 with commit 665fb7d22a700c66a78db0cf88c6e6a649aba9d0
	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 6.12.97 with commit e038d42cc09ca1da9d3568ce8ae062b2bfb3bc0e
	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 6.18.40 with commit e59a6aa89e0fcd1d0707832eb4654fd9ae7d31e6
	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 7.1.5 with commit 3525987a392536f31a484833af258971af63b24c
	Issue introduced in 4.8 with commit 8700e3e7c4857d28ebaa824509934556da0b3e76 and fixed in 7.2-rc1 with commit 35744ab3d03c5fca8c1752f53fc8fc674e14c561

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-64582
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/infiniband/sw/rxe/rxe_mmap.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/665fb7d22a700c66a78db0cf88c6e6a649aba9d0
	https://git.kernel.org/stable/c/e038d42cc09ca1da9d3568ce8ae062b2bfb3bc0e
	https://git.kernel.org/stable/c/e59a6aa89e0fcd1d0707832eb4654fd9ae7d31e6
	https://git.kernel.org/stable/c/3525987a392536f31a484833af258971af63b24c
	https://git.kernel.org/stable/c/35744ab3d03c5fca8c1752f53fc8fc674e14c561