On 04/02, Konstantin Khlebnikov wrote:
>
> Currently kernel does not account read-only private mappings into memory commitment.
> But these mappings can be force-COW-ed in get_user_pages().
Heh. tail -n3 Documentation/vm/overcommit-accounting
may be you should update it then.
Can't really comment the patch, this is not my area. Still,
> + down_write(&mm->mmap_sem);
> + *pvma = vma = find_vma(mm, addr);
> + if (vma && vma->vm_start <= addr) {
> + ret = vma->vm_end - addr;
> + if ((vma->vm_flags & (VM_ACCOUNT | VM_NORESERVE | VM_SHARED |
> + VM_HUGETLB | VM_MAYWRITE)) == VM_MAYWRITE) {
> + if (!security_vm_enough_memory_mm(mm, vma_pages(vma)))
Oooooh, the whole vma. Say, gdb installs the single breakpoint into
the huge .text mapping...
I am not sure, but probably you want to check at least VM_IO/PFNMAP
as well. We do not want to charge this memory and retry with FOLL_FORCE
before vm_ops->access(). Say, /dev/mem.
Hmm. OTOH, if I am right then mprotect_fixup() should be fixed??
We drop ->mmap_sem... Say, the task does mremap() in between and
len == 2 * PAGE_SIZE. Then, for example, copy_to_user_page() can
write to the same page twice. Perhaps not a problem in practice,
I dunno.
Oleg.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>