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Dan Carpenter reported that the untrusted data returns from kvm_register_read() results in the following static checker warning: arch/x86/kvm/lapic.c:576 kvm_pv_send_ipi() error: buffer underflow 'map->phys_map' 's32min-s32max' KVM guest can easily trigger this by executing the following assembly sequence in Ring0: mov $10, %rax mov $0xFFFFFFFF, %rbx mov $0xFFFFFFFF, %rdx mov $0, %rsi vmcall As this will cause KVM to execute the following code-path: vmx_handle_exit() -> handle_vmcall() -> kvm_emulate_hypercall() -> kvm_pv_send_ipi() which will reach out-of-bounds access. This patch fixes it by adding a check to kvm_pv_send_ipi() against map->max_apic_id, ignoring destinations that are not present and delivering the rest. We also check whether or not map->phys_map[min + i] is NULL since the max_apic_id is set to the max apic id, some phys_map maybe NULL when apic id is sparse, especially kvm unconditionally set max_apic_id to 255 to reserve enough space for any xAPIC ID. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Reviewed-by: Liran Alon <liran.alon@oracle.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: Liran Alon <liran.alon@oracle.com> Cc: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> [Add second "if (min > map->max_apic_id)" to complete the fix. -Radim] Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.