[PATCH] RLIMIT_AS checking fix
Address bug #4508: there's potential for wraparound in the various places
where we perform RLIMIT_AS checking.
(I'm a bit worried about acct_stack_growth(). Are we sure that vma->vm_mm is
always equal to current->mm? If not, then we're comparing some other
process's total_vm with the calling process's rlimits).
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/mmap.c b/mm/mmap.c
index 6ea204c..1ec0f6e 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1009,8 +1009,7 @@
}
/* Check against address space limit. */
- if ((mm->total_vm << PAGE_SHIFT) + len
- > current->signal->rlim[RLIMIT_AS].rlim_cur)
+ if (!may_expand_vm(mm, len >> PAGE_SHIFT))
return -ENOMEM;
if (accountable && (!(flags & MAP_NORESERVE) ||
@@ -1421,7 +1420,7 @@
struct rlimit *rlim = current->signal->rlim;
/* address space limit tests */
- if (mm->total_vm + grow > rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT)
+ if (!may_expand_vm(mm, grow))
return -ENOMEM;
/* Stack limit test */
@@ -1848,8 +1847,7 @@
}
/* Check against address space limits *after* clearing old maps... */
- if ((mm->total_vm << PAGE_SHIFT) + len
- > current->signal->rlim[RLIMIT_AS].rlim_cur)
+ if (!may_expand_vm(mm, len >> PAGE_SHIFT))
return -ENOMEM;
if (mm->map_count > sysctl_max_map_count)
@@ -2019,3 +2017,19 @@
}
return new_vma;
}
+
+/*
+ * 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 = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
+
+ if (cur + npages > lim)
+ return 0;
+ return 1;
+}