x86/mm/iommu/sva: Do not allow to set FORCE_TAGGED_SVA bit from outside

arch_prctl(ARCH_FORCE_TAGGED_SVA) overrides the default and allows LAM and SVA to co-exist in the process. It is expected by called by the process when it knows what it is doing. arch_prctl() operates on the current process, but the same code is reachable from ptrace where it can be called on arbitrary task. Make it strict and only allow to set MM_CONTEXT_FORCE_TAGGED_SVA for the current process. Fixes: 23e5d9e ("x86/mm/iommu/sva: Make LAM and SVA mutually exclusive") Suggested-by: Dmitry Vyukov <[email protected]> Signed-off-by: Kirill A. Shutemov <[email protected]> Signed-off-by: Dave Hansen <[email protected]> Reviewed-by: Dmitry Vyukov <[email protected]> Link: https://lore.kernel.org/all/20230403111020.3136-3-kirill.shutemov%40linux.intel.com
sirdarckcat · Apr 6, 2023 · 9774026 · 9774026
1 parent fca1fdd
commit 9774026
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
@@ -883,6 +883,8 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2)
 	case ARCH_ENABLE_TAGGED_ADDR:
 		return prctl_enable_tagged_addr(task->mm, arg2);
 	case ARCH_FORCE_TAGGED_SVA:
+		if (current != task)
+			return -EINVAL;
 		set_bit(MM_CONTEXT_FORCE_TAGGED_SVA, &task->mm->context.flags);
 		return 0;
 	case ARCH_GET_MAX_TAG_BITS: