When inspecting a vague code inside prctl(PR_SET_MM_MEM)
call (which testing the RLIMIT_DATA value to figure out
if we're allowed to assign new @start_brk, @brk, @start_data,
@end_data from mm_struct) it's been commited that RLIMIT_DATA
in a form it's implemented now doesn't do anything useful
because most of user-space libraries use mmap() syscall
for dynamic memory allocations.
So Linus suggested to convert RLIMIT_DATA rlimit into something
suitable for anonymous memory accounting. Here we introduce
new @anon_vm member into mm descriptor which is updated
on every vm_stat_account() call.
Tests for RLIMIT_DATA are done in three places:
- mmap_region: when user calls mmap() helper
- do_brk: for brk() helper
- vma_to_resize: when mremap() is used
The do_brk() is also used in vm_brk() which is called
when the kernel loads Elf and aout files to execute.
Because test for limit is done in do_brk helper we
no longer need to call check_data_rlimit here.
v2:
- update doc
- add may_expand_anon_vm helper
- call for RLIMIT_DATA test in mremap and do_brk
CC: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
CC: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
CC: Willy Tarreau <w@xxxxxx>
CC: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
CC: Kees Cook <keescook@xxxxxxxxxx>
CC: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
CC: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
CC: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
CC: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
---
Documentation/filesystems/proc.txt | 1
fs/proc/task_mmu.c | 2 +
include/linux/mm_types.h | 1
mm/mmap.c | 46 ++++++++++++++++++++++---------------
mm/mremap.c | 5 ++++
5 files changed, 37 insertions(+), 18 deletions(-)
Index: linux-ml.git/Documentation/filesystems/proc.txt
===================================================================
--- linux-ml.git.orig/Documentation/filesystems/proc.txt
+++ linux-ml.git/Documentation/filesystems/proc.txt
@@ -233,6 +233,7 @@ Table 1-2: Contents of the status files
VmHWM peak resident set size ("high water mark")
VmRSS size of memory portions
VmData size of data, stack, and text segments
+ VmAnon size of anonymous private memory (not file backended)
VmStk size of data, stack, and text segments
VmExe size of text segment
VmLib size of shared library code
Index: linux-ml.git/fs/proc/task_mmu.c
===================================================================
--- linux-ml.git.orig/fs/proc/task_mmu.c
+++ linux-ml.git/fs/proc/task_mmu.c
@@ -53,6 +53,7 @@ void task_mem(struct seq_file *m, struct
"VmHWM:\t%8lu kB\n"
"VmRSS:\t%8lu kB\n"
"VmData:\t%8lu kB\n"
+ "VmAnon:\t%8lu kB\n"
"VmStk:\t%8lu kB\n"
"VmExe:\t%8lu kB\n"
"VmLib:\t%8lu kB\n"
@@ -66,6 +67,7 @@ void task_mem(struct seq_file *m, struct
hiwater_rss << (PAGE_SHIFT-10),
total_rss << (PAGE_SHIFT-10),
data << (PAGE_SHIFT-10),
+ mm->anon_vm << (PAGE_SHIFT-10),
mm->stack_vm << (PAGE_SHIFT-10), text, lib,
ptes >> 10,
pmds >> 10,
Index: linux-ml.git/include/linux/mm_types.h
===================================================================
--- linux-ml.git.orig/include/linux/mm_types.h
+++ linux-ml.git/include/linux/mm_types.h
@@ -429,6 +429,7 @@ struct mm_struct {
unsigned long shared_vm; /* Shared pages (files) */
unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE */
unsigned long stack_vm; /* VM_GROWSUP/DOWN */
+ unsigned long anon_vm; /* Anonymous pages mapped */
unsigned long def_flags;
unsigned long start_code, end_code, start_data, end_data;
unsigned long start_brk, brk, start_stack;
Index: linux-ml.git/mm/mmap.c
===================================================================
--- linux-ml.git.orig/mm/mmap.c
+++ linux-ml.git/mm/mmap.c
@@ -309,16 +309,6 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
if (brk < min_brk)
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
- */
- if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
- mm->end_data, mm->start_data))
- goto out;
-
newbrk = PAGE_ALIGN(brk);
oldbrk = PAGE_ALIGN(mm->brk);
if (oldbrk == newbrk)
@@ -1223,6 +1213,9 @@ void vm_stat_account(struct mm_struct *m
mm->exec_vm += pages;
} else if (flags & stack_flags)
mm->stack_vm += pages;
+
+ if (anon_accountable_mapping(file, flags))
+ mm->anon_vm += pages;
}
#endif /* CONFIG_PROC_FS */
@@ -1578,6 +1571,14 @@ unsigned long mmap_region(struct file *f
}
/*
+ * For anon mappings make sure we don't exceed the limit.
+ */
+ if (anon_accountable_mapping(file, vm_flags)) {
+ if (!may_expand_anon_vm(mm, len >> PAGE_SHIFT))
+ return -ENOMEM;
+ }
+
+ /*
* Can we just expand an old mapping?
*/
vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
@@ -2760,7 +2761,8 @@ static unsigned long do_brk(unsigned lon
}
/* Check against address space limits *after* clearing old maps... */
- if (!may_expand_vm(mm, len >> PAGE_SHIFT))
+ if (!may_expand_vm(mm, len >> PAGE_SHIFT) ||
+ !may_expand_anon_vm(mm, len >> PAGE_SHIFT))
return -ENOMEM;
if (mm->map_count > sysctl_max_map_count)
@@ -2795,6 +2797,7 @@ static unsigned long do_brk(unsigned lon
out:
perf_event_mmap(vma);
mm->total_vm += len >> PAGE_SHIFT;
+ mm->anon_vm += len >> PAGE_SHIFT;
if (flags & VM_LOCKED)
mm->locked_vm += (len >> PAGE_SHIFT);
vma->vm_flags |= VM_SOFTDIRTY;
@@ -2982,20 +2985,27 @@ out:
return NULL;
}
+static inline int __may_expand_vm(unsigned int limit,
+ unsigned long cur,
+ unsigned long npages)
+{
+ unsigned long lim = rlimit(limit) >> PAGE_SHIFT;
+
+ return ((cur + npages) > lim) ? 0 : 1;
+}
+
/*
* Return true if the calling process may expand its vm space by the passed
* number of pages
*/
int may_expand_vm(struct mm_struct *mm, unsigned long npages)
{
- unsigned long cur = mm->total_vm; /* pages */
- unsigned long lim;
-
- lim = rlimit(RLIMIT_AS) >> PAGE_SHIFT;
+ return __may_expand_vm(RLIMIT_AS, mm->total_vm, npages);
+}
- if (cur + npages > lim)
- return 0;
- return 1;
+int may_expand_anon_vm(struct mm_struct *mm, unsigned long npages)
+{
+ return __may_expand_vm(RLIMIT_DATA, mm->anon_vm, npages);
}
static int special_mapping_fault(struct vm_area_struct *vma,
Index: linux-ml.git/mm/mremap.c
===================================================================
--- linux-ml.git.orig/mm/mremap.c
+++ linux-ml.git/mm/mremap.c
@@ -382,6 +382,11 @@ static struct vm_area_struct *vma_to_res
if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
return ERR_PTR(-ENOMEM);
+ if (anon_accountable_mapping(vma->vm_file, vma->vm_flags)) {
+ if (!may_expand_anon_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
+ return ERR_PTR(-ENOMEM);
+ }
+
if (vma->vm_flags & VM_ACCOUNT) {
unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
if (security_vm_enough_memory_mm(mm, charged))
--
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