The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: d4fc4d01471528da8a9797a065982e05090e1d81 Gitweb: https://git.kernel.org/tip/d4fc4d01471528da8a9797a065982e05090e1d81 Author: Alexey Gladkov (Intel) legion@kernel.org AuthorDate: Fri, 13 Sep 2024 19:05:56 +02:00 Committer: Dave Hansen dave.hansen@linux.intel.com CommitterDate: Thu, 26 Sep 2024 09:45:04 -07:00

x86/tdx: Fix "in-kernel MMIO" check

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... --- arch/x86/coco/tdx/tdx.c | 6 ++++++ 1 file changed, 6 insertions(+)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c index da8b66d..327c45c 100644 --- a/arch/x86/coco/tdx/tdx.c +++ b/arch/x86/coco/tdx/tdx.c @@ -16,6 +16,7 @@ #include <asm/insn-eval.h> #include <asm/pgtable.h> #include <asm/set_memory.h> +#include <asm/traps.h>

/* MMIO direction */ #define EPT_READ 0 @@ -433,6 +434,11 @@ static int handle_mmio(struct pt_regs *regs, struct ve_info *ve) 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. *