Commit cb1a393c authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Catalin Marinas
Browse files

mm: add arch hook to validate mmap() prot flags 



Add a hook to permit architectures to perform validation on the prot
flags passed to mmap(), like arch_validate_prot() does for mprotect().
This will be used by arm64 to reject PROT_WRITE+PROT_EXEC mappings on
configurations that run with WXN enabled.

Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20240214122845.2033971-87-ardb+git@google.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 5d101654

include/linux/mman.h

+15 −0
Original line number Diff line number Diff line
@@ -124,6 +124,21 @@ static inline bool arch_validate_flags(unsigned long flags) 
#define arch_validate_flags arch_validate_flags

#endif



#ifndef arch_validate_mmap_prot

/*

 * This is called from mmap(), which ignores unknown prot bits so the default

 * is to accept anything.

 *

 * Returns true if the prot flags are valid

 */

static inline bool arch_validate_mmap_prot(unsigned long prot,

					   unsigned long addr)

{

	return true;

}

#define arch_validate_mmap_prot arch_validate_mmap_prot

#endif



/*

 * Optimisation macro.  It is equivalent to:

 *      (x & bit1) ? bit2 : 0

mm/mmap.c

+3 −0
Original line number Diff line number Diff line
@@ -1229,6 +1229,9 @@ unsigned long do_mmap(struct file *file, unsigned long addr, 
		if (!(file && path_noexec(&file->f_path)))

			prot |= PROT_EXEC;



	if (!arch_validate_mmap_prot(prot, addr))

		return -EACCES;



	/* force arch specific MAP_FIXED handling in get_unmapped_area */

	if (flags & MAP_FIXED_NOREPLACE)

		flags |= MAP_FIXED;