linux-kernel - Re: [PATCH] VMCI: check context->notify_page after call to get_user_pages

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Date:   Tue, 29 Nov 2022 22:22:17 +0000
From:   Vishnu Dasa <vdasa@...are.com>
To:     George Kennedy <george.kennedy@...cle.com>
CC:     Bryan Tan <bryantan@...are.com>,
        Pv-drivers <Pv-drivers@...are.com>,
        "arnd@...db.de" <arnd@...db.de>,
        Greg KH <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] VMCI: check context->notify_page after call to
 get_user_pages_fast() to avoid GPF


> On Nov 28, 2022, at 12:18 PM, George Kennedy <george.kennedy@...cle.com> wrote:
> 
> The call to get_user_pages_fast() in vmci_host_setup_notify() can return
> NULL context->notify_page causing a GPF. To avoid GPF check if
> context->notify_page == NULL and return error if so.
> 
> general protection fault, probably for non-canonical address
>    0xe0009d1000000060: 0000 [#1] PREEMPT SMP KASAN NOPTI
> KASAN: maybe wild-memory-access in range [0x0005088000000300-
>    0x0005088000000307]
> CPU: 2 PID: 26180 Comm: repro_34802241 Not tainted 6.1.0-rc4 #1
> Hardware name: Red Hat KVM, BIOS 1.15.0-2.module+el8.6.0 04/01/2014
> RIP: 0010:vmci_ctx_check_signal_notify+0x91/0xe0
> Call Trace:
> <TASK>
> vmci_host_unlocked_ioctl+0x362/0x1f40
> __x64_sys_ioctl+0x1a1/0x230
> do_syscall_64+0x3a/0x90
> entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Fixes: a1d88436d53a ("VMCI: Fix two UVA mapping bugs")
> Reported-by: syzkaller <syzkaller@...glegroups.com>
> Signed-off-by: George Kennedy <george.kennedy@...cle.com>

Thanks for the fix!

Reviewed-by: Vishnu Dasa <vdasa@...are.com>

> ---
> drivers/misc/vmw_vmci/vmci_host.c | 2 ++
> 1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/misc/vmw_vmci/vmci_host.c b/drivers/misc/vmw_vmci/vmci_host.c
> index da1e2a773823..857b9851402a 100644
> --- a/drivers/misc/vmw_vmci/vmci_host.c
> +++ b/drivers/misc/vmw_vmci/vmci_host.c
> @@ -242,6 +242,8 @@ static int vmci_host_setup_notify(struct vmci_ctx *context,
> 		context->notify_page = NULL;
> 		return VMCI_ERROR_GENERIC;
> 	}
> +	if (context->notify_page == NULL)
> +		return VMCI_ERROR_UNAVAILABLE;
> 
> 	/*
> 	 * Map the locked page and set up notify pointer.
> -- 
> 2.31.1
>