Re: [PATCH] mm: include private data mappings in RLIMIT_DATA limit

[Randy Dunlap]

On Thu, 31 May 2007 12:43:16 -0700 Herbert van den Bergh wrote:

> Below is a patch I would like to submit for limiting process private 
> memory allocations via setrlimit(RLIMIT_DATA).
> 
> Thanks,
> Herbert van den Bergh.
> 
> 
> This patch changes how the kernel limits memory allocations that are
> controlled by setrlimit() using the RLIMIT_DATA resource.  Currently the
> kernel can limit the size of a process data, bss, and heap, but does not
> limit the amount of process private memory that can be allocated with
> the mmap() call.  Since malloc() calls mmap() to allocate process memory
> once brk() calls can no longer grow the heap, process private memory
> allocations cannot be limited with RLIMIT_DATA.
> 
> With this patch, not only memory in the data segment of a process, but
> also private data mappings, both file-based and anonymous, are counted
> toward the RLIMIT_DATA resource limit.  Executable mappings, such as
> text segments of shared objects, are not counted toward the private data
> limit.  The result is that malloc() will fail once the combined size of
> the data segment and private data mappings reaches this limit.
> 
> This brings the Linux behavior in line with what is documented in the
> POSIX man page for setrlimit(3p).
> 
> Signed-off-by: Herbert van den Bergh (herbert.van.den.bergh@xxxxxxxxxx)
> Signed-off-by: Dave McCracken (dave.mccracken@xxxxxxxxxx)
> 

Howdy,

The patch seems to have all tabs converted to spaces.
This could be caused by thunderbird or by copy-and-pasting.

Tbird needs help for sending patches without munging them.
See http://mbligh.org/linuxdocs/Email/Clients/Thunderbird
or google for "external editor" and use that with a decent
text editor.

Maybe it doesn't matter for this patch, but in general you
should send patches made against the latest mainline kernel,
such as 2.6.22-rc3 or 2.6.22-rc3-git4 or current git tree.

There are a few lines that are > 80 characters.  Please try
to avoid that.

 ----------------------------------------------------------------------------------
> --- linux-2.6.21/fs/proc/task_mmu.c.orig        2007-05-29 21:05:31.000000000 -0700
> +++ linux-2.6.21/fs/proc/task_mmu.c     2007-05-30 08:17:44.000000000 -0700
> @@ -31,7 +31,7 @@
>         if (hiwater_rss < mm->hiwater_rss)
>                 hiwater_rss = mm->hiwater_rss;
> 
> -       data = mm->total_vm - mm->shared_vm - mm->stack_vm;
> +       data = mm->total_vm - mm->shared_vm - mm->stack_vm - mm->exec_vm;
>         text = (PAGE_ALIGN(mm->end_code) - (mm->start_code & PAGE_MASK)) >> 10;
>         lib = (mm->exec_vm << (PAGE_SHIFT-10)) - text;
>         buffer += sprintf(buffer,
> --- linux-2.6.21/mm/mprotect.c.orig     2007-04-25 20:08:32.000000000 -0700
> +++ linux-2.6.21/mm/mprotect.c  2007-05-30 08:34:36.000000000 -0700
> @@ -162,6 +162,21 @@
>                 }
>         }
> 
> +        /*
> +        * Check against private data size limit. When execute permission
> +        * is removed, the mapping is counted toward the private data size.
> +        */
> +       if (!(newflags & VM_EXEC) && (vma->vm_flags & VM_EXEC)) {
> +               unsigned long rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
> +               if (rlim < RLIM_INFINITY) {
> +                       unsigned long priv_vm;
> +                       priv_vm = mm->total_vm - mm->shared_vm - mm->exec_vm;
> +                       priv_vm <<= PAGE_SHIFT;
> +                       if (priv_vm + (end - start) > rlim)
> +                               return -ENOMEM;
> +               }
> +        }
> +
>         /*
>          * First try to merge with previous and/or next vma.
>          */
> --- linux-2.6.21/mm/mremap.c.orig       2007-04-25 20:08:32.000000000 -0700
> +++ linux-2.6.21/mm/mremap.c    2007-05-30 08:38:28.000000000 -0700
> @@ -343,6 +343,22 @@
>                 goto out;
>         }
> 
> +        /*
> +        * Check against private data size limit. Count memory allocations
> +        * which are not shared and not executable code as private data.
> +        */
> +       if (!(vma->vm_flags & (VM_EXEC|VM_SHARED))) {
> +               unsigned long rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
> +               if (rlim < RLIM_INFINITY) {
> +                       unsigned long priv_vm;
> +                       struct mm_struct *mm = current->mm;
> +                       priv_vm = mm->total_vm - mm->shared_vm - mm->exec_vm;
> +                       priv_vm <<= PAGE_SHIFT;
> +                       if (priv_vm + (new_len - old_len) > rlim)
> +                               goto out;
> +               }
> +        }
> +
>         if (vma->vm_flags & VM_ACCOUNT) {
>                 charged = (new_len - old_len) >> PAGE_SHIFT;
>                 if (security_vm_enough_memory(charged))
> --- linux-2.6.21/mm/mmap.c.orig 2007-05-29 21:05:58.000000000 -0700
> +++ linux-2.6.21/mm/mmap.c      2007-05-30 08:27:55.000000000 -0700
> @@ -245,16 +245,6 @@
>         if (brk < mm->end_code)
>                 goto out;
> 
> -       /*
> -        * Check against rlimit here. If this check is done later after the test
> -        * of oldbrk with newbrk then it can escape the test and let the data
> -        * segment grow beyond its set limit the in case where the limit is
> -        * not page aligned -Ram Gupta
> -        */
> -       rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
> -       if (rlim < RLIM_INFINITY && brk - mm->start_data > rlim)
> -               goto out;
> -
>         newbrk = PAGE_ALIGN(brk);
>         oldbrk = PAGE_ALIGN(mm->brk);
>         if (oldbrk == newbrk)
> @@ -267,6 +257,18 @@
>                 goto out;
>         }
> 
> +        /*
> +        * Check against private data size limit. Count memory allocations
> +        * which are not shared and not executable code as private data.
> +        */
> +        rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
> +        if (rlim < RLIM_INFINITY) {
> +            unsigned long priv_vm;
> +            priv_vm = (mm->total_vm - mm->shared_vm - mm->exec_vm) << PAGE_SHIFT;
> +            if (priv_vm + (newbrk-oldbrk) > rlim)
> +                goto out;
> +        }
> +
>         /* Check against existing mmap mappings. */
>         if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
>                 goto out;
> @@ -875,7 +877,8 @@
>                 = VM_STACK_FLAGS & (VM_GROWSUP|VM_GROWSDOWN);
> 
>         if (file) {
> -               mm->shared_vm += pages;
> +               if (flags & VM_SHARED)
> +                       mm->shared_vm += pages;
>                 if ((flags & (VM_EXEC|VM_WRITE)) == VM_EXEC)
>                         mm->exec_vm += pages;
>         } else if (flags & stack_flags)
> @@ -1041,6 +1044,20 @@
>         if (!may_expand_vm(mm, len >> PAGE_SHIFT))
>                 return -ENOMEM;
> 
> +        /*
> +        * Check against private data size limit. Count memory allocations
> +        * which are not shared and not executable code as private data.
> +        */
> +       if (!(vm_flags & (VM_SHARED|VM_EXEC))) {
> +            unsigned long rlim, priv_vm;
> +            rlim = current->signal->rlim[RLIMIT_DATA].rlim_cur;
> +           if (rlim < RLIM_INFINITY) {
> +                priv_vm = (mm->total_vm - mm->shared_vm - mm->exec_vm) << PAGE_SHIFT;
> +                if (priv_vm + len > rlim)
> +                   return -ENOMEM;
> +            }
> +        }
> +
>         if (accountable && (!(flags & MAP_NORESERVE) ||
>                             sysctl_overcommit_memory == OVERCOMMIT_NEVER)) {
>                 if (vm_flags & VM_SHARED) {
> 
> 
> -

---
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
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