From b6b7a8faf05c709cd9f63d3b7d9c66bd91bc3b0d Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Mon, 2 Jan 2023 17:08:55 +0100 Subject: mm/nommu: don't use VM_MAYSHARE for MAP_PRIVATE mappings Let's stop using VM_MAYSHARE for MAP_PRIVATE mappings and use VM_MAYOVERLAY instead. Rewrite determine_vm_flags() to make the whole logic easier to digest, and to cleanly separate MAP_PRIVATE vs. MAP_SHARED. No functional change intended. Link: https://lkml.kernel.org/r/20230102160856.500584-3-david@redhat.com Signed-off-by: David Hildenbrand Cc: Arnd Bergmann Cc: Greg Kroah-Hartman Cc: Jens Axboe Cc: Nicolas Pitre Cc: Pavel Begunkov Signed-off-by: Andrew Morton --- include/linux/mm.h | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/mm.h b/include/linux/mm.h index 791bac40bf8e..8a8563359946 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -276,7 +276,12 @@ extern unsigned int kobjsize(const void *objp); #define VM_MAYSHARE 0x00000080 #define VM_GROWSDOWN 0x00000100 /* general info on the segment */ +#ifdef CONFIG_MMU #define VM_UFFD_MISSING 0x00000200 /* missing pages tracking */ +#else /* CONFIG_MMU */ +#define VM_MAYOVERLAY 0x00000200 /* nommu: R/O MAP_PRIVATE mapping that might overlay a file mapping */ +#define VM_UFFD_MISSING 0 +#endif /* CONFIG_MMU */ #define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */ #define VM_UFFD_WP 0x00001000 /* wrprotect pages tracking */ @@ -1358,7 +1363,7 @@ static inline bool is_nommu_shared_mapping(vm_flags_t flags) * ptrace does not apply. Note that there is no mprotect() to upgrade * write permissions later. */ - return flags & VM_MAYSHARE; + return flags & (VM_MAYSHARE | VM_MAYOVERLAY); } #endif -- cgit v1.2.3