[Xen-devel] [PATCH] xen: Prevent buffer overflow in privcmd ioctl

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

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.

Fixes: 1246ae0bb992 ("xen: add variable hypercall caller")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
 arch/x86/include/asm/xen/hypercall.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/include/asm/xen/hypercall.h 
b/arch/x86/include/asm/xen/hypercall.h
index de6f0d59a24f..2863c2026655 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -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])
-- 
2.17.1


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