Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1315565 > unrolled thread

[PATCH v2] mm: warn about VmData over RLIMIT_DATA

Back to article view | Back to linux.kernel

Contents

  [PATCH v2] mm: warn about VmData over RLIMIT_DATA Konstantin Khlebnikov <koct9i@gmail.com> - 2016-01-23 11:10 +0100
    Re: [PATCH v2] mm: warn about VmData over RLIMIT_DATA Linus Torvalds <torvalds@linux-foundation.org> - 2016-01-23 20:00 +0100

#1315565 — [PATCH v2] mm: warn about VmData over RLIMIT_DATA

This patch fixes 84638335900f ("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_DATA check (limit actually in bytes, not pages)
and by default turns it into warning which prints at first VmData misuse.
Like: "VmData 516096 exceeds RLIMIT_DATA 512000"

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".

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>
---
 Documentation/kernel-parameters.txt |    5 +++++
 mm/mmap.c                           |   12 +++++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index cfb2c0f1a4a8..d728caf7aa52 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1461,6 +1461,11 @@ 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 private mappings,
+			print warning at first misuse. Could be changed by
+			/sys/module/kernel/parameters/ignore_rlimit_data.
+
 	ihash_entries=	[KNL]
 			Set number of hash buckets for inode cache.
 
diff --git a/mm/mmap.c b/mm/mmap.c
index 84b12624ceb0..46d2ed6cb0df 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -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 +2985,12 @@ 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 ((flags & (VM_WRITE | VM_SHARED |
+		(VM_STACK_FLAGS & (VM_GROWSUP | VM_GROWSDOWN)))) == VM_WRITE &&
+	    mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT &&
+	    !WARN_ONCE(ignore_rlimit_data, "VmData %lu exceeds RLIMIT_DATA %lu",
+		       (mm->data_vm + npages)<<PAGE_SHIFT, rlimit(RLIMIT_DATA)))
+		return false;
 
 	return true;
 }

[toc] | [next] | [standalone]

#1315727

On Sat, Jan 23, 2016 at 2:00 AM, Konstantin Khlebnikov <koct9i@gmail.com> wrote:
> +       if ((flags & (VM_WRITE | VM_SHARED |
> +               (VM_STACK_FLAGS & (VM_GROWSUP | VM_GROWSDOWN)))) == VM_WRITE &&
> +           mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT &&
> +           !WARN_ONCE(ignore_rlimit_data, "VmData %lu exceeds RLIMIT_DATA %lu",
> +                      (mm->data_vm + npages)<<PAGE_SHIFT, rlimit(RLIMIT_DATA)))
> +               return false;

This needs to be rewritten as an inline helper function or made
readable some other way.

It looks like line noise (or perl). That kind of code should not exist.

                  Linus

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web