Content-Description: Forwarded message - TASK_SIZE is variable.
> Date: Tue, 25 Jan 2005 22:26:52 +0000
> From: David Woodhouse <[EMAIL PROTECTED]>
> Subject: TASK_SIZE is variable.
> To: linux-arch@vger.kernel.org
> X-Mailer: Evolution 2.0.2 (2.0.2-3.dwmw2.1)
>
> Bad things can happen if a 32-bit process is the last user of a 64-bit
> mm. TASK_SIZE isn't a constant, and we can end up clearing page tables
> only up to the 32-bit TASK_SIZE instead of all the way. We should
> probably double-check every instance of TASK_SIZE or USER_PTRS_PER_PGD
> for this kind of problem.
Or better get rid of TASK_SIZE completely. Having something that looks
like a constant change depending on the user process is a bad idea.
> We should also double-check that MM_VM_SIZE() and other such things are
> correctly defined on all architectures. I already fixed ppc64 which let
> it stay as TASK_SIZE, and hence dependent on the _current_ context
> instead of the mm in the argument.
>
> --- mm/mmap.c.orig 2005-01-25 22:23:02.030427272 +0000
> +++ mm/mmap.c 2005-01-25 22:23:55.627279312 +0000
> @@ -1612,8 +1612,8 @@ static void free_pgtables(struct mmu_gat
> unsigned long last = end + PGDIR_SIZE - 1;
> struct mm_struct *mm = tlb->mm;
>
> - if (last > TASK_SIZE || last < end)
> - last = TASK_SIZE;
> + if (last > MM_VM_SIZE(mm) || last < end)
> + last = MM_VM_SIZE(mm);
>
> if (!prev) {
> prev = mm->mmap;
> @@ -1996,7 +1996,7 @@ void exit_mmap(struct mm_struct *mm)
> vm_unacct_memory(nr_accounted);
> BUG_ON(mm->map_count); /* This is just debugging */
> clear_page_range(tlb, FIRST_USER_PGD_NR * PGDIR_SIZE,
> - (TASK_SIZE + PGDIR_SIZE - 1) & PGDIR_MASK);
> + (MM_VM_SIZE(mm) + PGDIR_SIZE - 1) & PGDIR_MASK);
>
> tlb_finish_mmu(tlb, 0, MM_VM_SIZE(mm));
>
>
> --
> dwmw2
-
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