6.6-stable review patch. If anyone has any objections, please let me know.
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From: Alexey Gladkov (Intel) legion@kernel.org
commit d4fc4d01471528da8a9797a065982e05090e1d81 upstream.
TDX only supports kernel-initiated MMIO operations. The handle_mmio() function checks if the #VE exception occurred in the kernel and rejects the operation if it did not.
However, userspace can deceive the kernel into performing MMIO on its behalf. For example, if userspace can point a syscall to an MMIO address, syscall does get_user() or put_user() on it, triggering MMIO #VE. The kernel will treat the #VE as in-kernel MMIO.
Ensure that the target MMIO address is within the kernel before decoding instruction.
Fixes: 31d58c4e557d ("x86/tdx: Handle in-kernel MMIO") Signed-off-by: Alexey Gladkov (Intel) legion@kernel.org Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Reviewed-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Acked-by: Dave Hansen dave.hansen@linux.intel.com Cc:stable@vger.kernel.org Link: https://lore.kernel.org/all/565a804b80387970460a4ebc67c88d1380f61ad1.1726237... Signed-off-by: Alexey Gladkov (Intel) legion@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/coco/tdx/tdx.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -14,6 +14,7 @@ #include <asm/insn.h> #include <asm/insn-eval.h> #include <asm/pgtable.h> +#include <asm/traps.h>
/* MMIO direction */ #define EPT_READ 0 @@ -405,6 +406,11 @@ static int handle_mmio(struct pt_regs *r return -EINVAL; }
+ if (!fault_in_kernel_space(ve->gla)) { + WARN_ONCE(1, "Access to userspace address is not supported"); + return -EINVAL; + } + /* * Reject EPT violation #VEs that split pages. *