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mm: warn about VmData over RLIMIT_DATA 

This patch provides a way of working around a slight regression
introduced by commit 8463833590 ("mm: rework virtual memory
accounting").

Before that commit RLIMIT_DATA have control only over size of the brk
region.  But that change have caused problems with all existing versions
of valgrind, because it set RLIMIT_DATA to zero.

This patch fixes rlimit check (limit actually in bytes, not pages) and
by default turns it into warning which prints at first VmData misuse:

  "mmap: top (795): VmData 516096 exceed data ulimit 512000.  Will be forbidden soon."

Behavior is controlled by boot param ignore_rlimit_data=y/n and by sysfs
/sys/module/kernel/parameters/ignore_rlimit_data.  For now it set to "y".

[akpm@linux-foundation.org: tweak kernel-parameters.txt text[
Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
Link: http://lkml.kernel.org/r/20151228211015.GL2194@uranus
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Kees Cook <keescook@google.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Konstantin Khlebnikov 2016-02-02 16:57:43 -08:00 committed by Linus Torvalds
parent 4758e198ad
commit d977d56ce5
3 changed files with 38 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
Documentation/kernel-parameters.txt
View File

@ -1496,6 +1496,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
could change it dynamically, usually by
/sys/module/printk/parameters/ignore_loglevel.
ignore_rlimit_data
Ignore RLIMIT_DATA setting for data mappings,
print warning at first misuse. Can be changed via
/sys/module/kernel/parameters/ignore_rlimit_data.
ihash_entries= [KNL]
Set number of hash buckets for inode cache.

16
mm/internal.h
View File

@ -216,6 +216,22 @@ static inline bool is_cow_mapping(vm_flags_t flags)
return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
}
static inline bool is_exec_mapping(vm_flags_t flags)
{
return (flags & (VM_EXEC | VM_WRITE)) == VM_EXEC;
}
static inline bool is_stack_mapping(vm_flags_t flags)
{
return (flags & (VM_STACK_FLAGS & (VM_GROWSUP | VM_GROWSDOWN))) != 0;
}
static inline bool is_data_mapping(vm_flags_t flags)
{
return (flags & ((VM_STACK_FLAGS & (VM_GROWSUP | VM_GROWSDOWN)) |
VM_WRITE | VM_SHARED)) == VM_WRITE;
}
/* mm/util.c */
void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev, struct rb_node *rb_parent);

23
mm/mmap.c
View File

@ -42,6 +42,7 @@
#include <linux/memory.h>
#include <linux/printk.h>
#include <linux/userfaultfd_k.h>
#include <linux/moduleparam.h>
#include <asm/uaccess.h>
#include <asm/cacheflush.h>
@ -69,6 +70,8 @@ const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
#endif
static bool ignore_rlimit_data = true;
core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
static void unmap_region(struct mm_struct *mm,
struct vm_area_struct *vma, struct vm_area_struct *prev,
@ -2982,9 +2985,17 @@ bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
return false;
if ((flags & (VM_WRITE | VM_SHARED | (VM_STACK_FLAGS &
(VM_GROWSUP | VM_GROWSDOWN)))) == VM_WRITE)
return mm->data_vm + npages <= rlimit(RLIMIT_DATA);
if (is_data_mapping(flags) &&
mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
if (ignore_rlimit_data)
pr_warn_once("%s (%d): VmData %lu exceed data ulimit "
"%lu. Will be forbidden soon.\n",
current->comm, current->pid,
(mm->data_vm + npages) << PAGE_SHIFT,
rlimit(RLIMIT_DATA));
else
return false;
}
return true;
}
@ -2993,11 +3004,11 @@ void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
{
mm->total_vm += npages;
if ((flags & (VM_EXEC | VM_WRITE)) == VM_EXEC)
if (is_exec_mapping(flags))
mm->exec_vm += npages;
else if (flags & (VM_STACK_FLAGS & (VM_GROWSUP | VM_GROWSDOWN)))
else if (is_stack_mapping(flags))
mm->stack_vm += npages;
else if ((flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
else if (is_data_mapping(flags))
mm->data_vm += npages;
}