From 24e41bf8a6b424c76c5902fb999e9eca61bdf83d Mon Sep 17 00:00:00 2001 From: Florent Revest Date: Mon, 28 Aug 2023 17:08:57 +0200 Subject: mm: add a NO_INHERIT flag to the PR_SET_MDWE prctl This extends the current PR_SET_MDWE prctl arg with a bit to indicate that the process doesn't want MDWE protection to propagate to children. To implement this no-inherit mode, the tag in current->mm->flags must be absent from MMF_INIT_MASK. This means that the encoding for "MDWE but without inherit" is different in the prctl than in the mm flags. This leads to a bit of bit-mangling in the prctl implementation. Link: https://lkml.kernel.org/r/20230828150858.393570-6-revest@chromium.org Signed-off-by: Florent Revest Reviewed-by: Kees Cook Reviewed-by: Catalin Marinas Cc: Alexey Izbyshev Cc: Anshuman Khandual Cc: Ayush Jain Cc: David Hildenbrand Cc: Greg Thelen Cc: Joey Gouly Cc: KP Singh Cc: Mark Brown Cc: Michal Hocko Cc: Peter Xu Cc: Ryan Roberts Cc: Szabolcs Nagy Cc: Topi Miettinen Signed-off-by: Andrew Morton --- include/linux/sched/coredump.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/linux') diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h index 0ee96ea7a0e9..1b37fa8fc723 100644 --- a/include/linux/sched/coredump.h +++ b/include/linux/sched/coredump.h @@ -91,4 +91,14 @@ static inline int get_dumpable(struct mm_struct *mm) MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK) #define MMF_VM_MERGE_ANY 29 +#define MMF_HAS_MDWE_NO_INHERIT 30 + +static inline unsigned long mmf_init_flags(unsigned long flags) +{ + if (flags & (1UL << MMF_HAS_MDWE_NO_INHERIT)) + flags &= ~((1UL << MMF_HAS_MDWE) | + (1UL << MMF_HAS_MDWE_NO_INHERIT)); + return flags & MMF_INIT_MASK; +} + #endif /* _LINUX_SCHED_COREDUMP_H */ -- cgit