[lts88] vsock fixes for CVE-2025-21756 #250
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jira VULN-53604 cve CVE-2025-21756 commit-author Michal Luczaj <mhal@rbox.co> commit fcdd224 upstream-diff Indentation is different from upstream change because this kernel lacks 135ffc7 ("bpf, vsock: Invoke proto::close on close()"). Otherwise the change content is the same. Preserve sockets bindings; this includes both resulting from an explicit bind() and those implicitly bound through autobind during connect(). Prevents socket unbinding during a transport reassignment, which fixes a use-after-free: 1. vsock_create() (refcnt=1) calls vsock_insert_unbound() (refcnt=2) 2. transport->release() calls vsock_remove_bound() without checking if sk was bound and moved to bound list (refcnt=1) 3. vsock_bind() assumes sk is in unbound list and before __vsock_insert_bound(vsock_bound_sockets()) calls __vsock_remove_bound() which does: list_del_init(&vsk->bound_table); // nop sock_put(&vsk->sk); // refcnt=0 BUG: KASAN: slab-use-after-free in __vsock_bind+0x62e/0x730 Read of size 4 at addr ffff88816b46a74c by task a.out/2057 dump_stack_lvl+0x68/0x90 print_report+0x174/0x4f6 kasan_report+0xb9/0x190 __vsock_bind+0x62e/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Allocated by task 2057: kasan_save_stack+0x1e/0x40 kasan_save_track+0x10/0x30 __kasan_slab_alloc+0x85/0x90 kmem_cache_alloc_noprof+0x131/0x450 sk_prot_alloc+0x5b/0x220 sk_alloc+0x2c/0x870 __vsock_create.constprop.0+0x2e/0xb60 vsock_create+0xe4/0x420 __sock_create+0x241/0x650 __sys_socket+0xf2/0x1a0 __x64_sys_socket+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Freed by task 2057: kasan_save_stack+0x1e/0x40 kasan_save_track+0x10/0x30 kasan_save_free_info+0x37/0x60 __kasan_slab_free+0x4b/0x70 kmem_cache_free+0x1a1/0x590 __sk_destruct+0x388/0x5a0 __vsock_bind+0x5e1/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e refcount_t: addition on 0; use-after-free. WARNING: CPU: 7 PID: 2057 at lib/refcount.c:25 refcount_warn_saturate+0xce/0x150 RIP: 0010:refcount_warn_saturate+0xce/0x150 __vsock_bind+0x66d/0x730 vsock_bind+0x97/0xe0 __sys_bind+0x154/0x1f0 __x64_sys_bind+0x6e/0xb0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e refcount_t: underflow; use-after-free. WARNING: CPU: 7 PID: 2057 at lib/refcount.c:28 refcount_warn_saturate+0xee/0x150 RIP: 0010:refcount_warn_saturate+0xee/0x150 vsock_remove_bound+0x187/0x1e0 __vsock_release+0x383/0x4a0 vsock_release+0x90/0x120 __sock_release+0xa3/0x250 sock_close+0x14/0x20 __fput+0x359/0xa80 task_work_run+0x107/0x1d0 do_exit+0x847/0x2560 do_group_exit+0xb8/0x250 __x64_sys_exit_group+0x3a/0x50 x64_sys_call+0xfec/0x14f0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Fixes: c0cfa2d ("vsock: add multi-transports support") Reviewed-by: Stefano Garzarella <sgarzare@redhat.com> Signed-off-by: Michal Luczaj <mhal@rbox.co> Link: https://patch.msgid.link/20250128-vsock-transport-vs-autobind-v3-1-1cf57065b770@rbox.co Signed-off-by: Jakub Kicinski <kuba@kernel.org> (cherry picked from commit fcdd224) Signed-off-by: Brett Mastbergen <bmastbergen@ciq.com>
jira VULN-53604 cve CVE-2025-21756 commit-author Michal Luczaj <mhal@rbox.co> commit 78dafe1 upstream-diff Indentation is different from upstream change because this kernel lacks 135ffc7 ("bpf, vsock: Invoke proto::close on close()"). Otherwise the change content is the same. During socket release, sock_orphan() is called without considering that it sets sk->sk_wq to NULL. Later, if SO_LINGER is enabled, this leads to a null pointer dereferenced in virtio_transport_wait_close(). Orphan the socket only after transport release. Partially reverts the 'Fixes:' commit. KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f] lock_acquire+0x19e/0x500 _raw_spin_lock_irqsave+0x47/0x70 add_wait_queue+0x46/0x230 virtio_transport_release+0x4e7/0x7f0 __vsock_release+0xfd/0x490 vsock_release+0x90/0x120 __sock_release+0xa3/0x250 sock_close+0x14/0x20 __fput+0x35e/0xa90 __x64_sys_close+0x78/0xd0 do_syscall_64+0x93/0x1b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e Reported-by: syzbot+9d55b199192a4be7d02c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=9d55b199192a4be7d02c Fixes: fcdd224 ("vsock: Keep the binding until socket destruction") Tested-by: Luigi Leonardi <leonardi@redhat.com> Reviewed-by: Luigi Leonardi <leonardi@redhat.com> Signed-off-by: Michal Luczaj <mhal@rbox.co> Link: https://patch.msgid.link/20250210-vsock-linger-nullderef-v3-1-ef6244d02b54@rbox.co Signed-off-by: Jakub Kicinski <kuba@kernel.org> (cherry picked from commit 78dafe1) Signed-off-by: Brett Mastbergen <bmastbergen@ciq.com>
kerneltoast
approved these changes
May 6, 2025
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VULN-53604
CVE-2025-21756
This ended up being two commits: The initial fix and a fix for that fix.
Build Log
Testing
kselftests were run before and after applying the fixes
selftests-4.18.0-477.27.1.el8_8.88ciq_lts.4.1.x86_64.log
selftests-4.18.0-bmastbergen_ciqlts8_8_VULN-53604-44d74af87cd5+.log