Commit d977d56c authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Linus Torvalds
Browse files

mm: warn about VmData over RLIMIT_DATA 



This patch provides a way of working around a slight regression
introduced by commit 84638335 ("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: default avatarKonstantin Khlebnikov <koct9i@gmail.com>
Link: http://lkml.kernel.org/r/20151228211015.GL2194@uranus


Reported-by: default avatarChristian 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4758e198

Documentation/kernel-parameters.txt

+5 −0
Original line number Diff line number Diff line
@@ -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.

mm/internal.h

+16 −0
Original line number Diff line number Diff line
@@ -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);

mm/mmap.c

+17 −6
Original line number Diff line number Diff line
@@ -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;

}

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