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xen: Prevent buffer overflow in privcmd ioctl

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The "call" variable comes from the user in privcmd_ioctl_hypercall().
It's an offset into the hypercall_page[] which has (PAGE_SIZE / 32)
elements.  We need to put an upper bound on it to prevent an out of
bounds access.

Cc: stable@vger.kernel.org
Fixes: 1246ae0bb992 ("xen: add variable hypercall caller")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Dan Carpenter 2019-04-04 18:12:17 +03:00 committed by Juergen Gross
parent ad94dc3a7e
commit 42d8644bd7
1 changed files with 3 additions and 0 deletions
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3
arch/x86/include/asm/xen/hypercall.h
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@ -206,6 +206,9 @@ xen_single_call(unsigned int call,
__HYPERCALL_DECLS;
__HYPERCALL_5ARG(a1, a2, a3, a4, a5);
if (call >= PAGE_SIZE / sizeof(hypercall_page[0]))
return -EINVAL;
asm volatile(CALL_NOSPEC
: __HYPERCALL_5PARAM
: [thunk_target] "a" (&hypercall_page[call])