[PATCH v5.10 v2] powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.

[Greg KH]

On Tue, Aug 06, 2024 at 07:16:16AM +0000, Jinjie Ruan wrote:
> From: Mahesh Salgaonkar <mahesh at linux.ibm.com>
> 
> [ Upstream commit 0db880fc865ffb522141ced4bfa66c12ab1fbb70 ]
> 
> nmi_enter()/nmi_exit() touches per cpu variables which can lead to kernel
> crash when invoked during real mode interrupt handling (e.g. early HMI/MCE
> interrupt handler) if percpu allocation comes from vmalloc area.
> 
> Early HMI/MCE handlers are called through DEFINE_INTERRUPT_HANDLER_NMI()
> wrapper which invokes nmi_enter/nmi_exit calls. We don't see any issue when
> percpu allocation is from the embedded first chunk. However with
> CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there are chances where percpu
> allocation can come from the vmalloc area.
> 
> With kernel command line "percpu_alloc=page" we can force percpu allocation
> to come from vmalloc area and can see kernel crash in machine_check_early:
> 
> [    1.215714] NIP [c000000000e49eb4] rcu_nmi_enter+0x24/0x110
> [    1.215717] LR [c0000000000461a0] machine_check_early+0xf0/0x2c0
> [    1.215719] --- interrupt: 200
> [    1.215720] [c000000fffd73180] [0000000000000000] 0x0 (unreliable)
> [    1.215722] [c000000fffd731b0] [0000000000000000] 0x0
> [    1.215724] [c000000fffd73210] [c000000000008364] machine_check_early_common+0x134/0x1f8
> 
> Fix this by avoiding use of nmi_enter()/nmi_exit() in real mode if percpu
> first chunk is not embedded.
> 
> CVE-2024-42126
> Cc: stable at vger.kernel.org#5.10.x
> Cc: gregkh at linuxfoundation.org
> Reviewed-by: Christophe Leroy <christophe.leroy at csgroup.eu>
> Tested-by: Shirisha Ganta <shirisha at linux.ibm.com>
> Signed-off-by: Mahesh Salgaonkar <mahesh at linux.ibm.com>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> Link: https://msgid.link/20240410043006.81577-1-mahesh@linux.ibm.com
> [ Conflicts in arch/powerpc/include/asm/interrupt.h
>   because machine_check_early() and machine_check_exception()
>   has been refactored. ]
> Signed-off-by: Jinjie Ruan <ruanjinjie at huawei.com>
> ---
> v2:
> - Also fix for CONFIG_PPC_BOOK3S_64 not enabled.
> - Add Upstream.
> - Cc stable at vger.kernel.org.

You forgot a 5.15.y version, which is of course required if we were to
take a 5.10.y version :(

Please resubmit both.

thanks,

greg k-h