Hi,
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 680506faceae..2649c00581a0 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1389,6 +1389,18 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
> struct inode *inode = file_inode(file);
>
> switch (flags & MAP_TYPE) {
> + case MAP_SHARED_VALIDATE:
> + if ((flags & ~LEGACY_MAP_MASK) == 0) {
> + /*
> + * If all legacy mmap flags, downgrade
> + * to MAP_SHARED, i.e. invoke ->mmap()
> + * instead of ->mmap_validate()
> + */
> + flags &= ~MAP_TYPE;
> + flags |= MAP_SHARED;
> + } else if (!file->f_op->mmap_validate)
> + return -EOPNOTSUPP;
> + /* fall through */
> case MAP_SHARED:
> if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
> return -EACCES;
When thinking a bit more about this I've realized one problem: Currently
user can call mmap() with MAP_SHARED type and MAP_SYNC or MAP_DIRECT flags
and he will get the new semantics (if the kernel happens to support it). I
think that is undesirable and we should force usage of MAP_SHARED_VALIDATE
when you want to use flags outside of LEGACY_MAP_MASK. So I'd just mask off
non-legacy flags for MAP_SHARED mappings (so they would be silently ignored
as they used to be until now).
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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