From 731572d39fcd3498702eda4600db4c43d51e0b26 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@redhat.com>
Date: Wed, 29 Oct 2008 14:01:20 -0700
Subject: [PATCH] nfsd: fix vm overcommit crash
Junjiro R. Okajima reported a problem where knfsd crashes if you are
using it to export shmemfs objects and run strict overcommit. In this
situation the current->mm based modifier to the overcommit goes through a
NULL pointer.
We could simply check for NULL and skip the modifier but we've caught
other real bugs in the past from mm being NULL here - cases where we did
need a valid mm set up (eg the exec bug about a year ago).
To preserve the checks and get the logic we want shuffle the checking
around and add a new helper to the vm_ security wrappers
Also fix a current->mm reference in nommu that should use the passed mm
[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix build]
Reported-by: Junjiro R. Okajima <hooanon05@yahoo.co.jp>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
include/linux/security.h | 6 ++++++
mm/mmap.c | 3 ++-
mm/nommu.c | 3 ++-
mm/shmem.c | 8 ++++----
security/security.c | 9 +++++++++
5 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index f5c4a51eb42ea..c13f1cec9abb1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -1585,6 +1585,7 @@ int security_syslog(int type);
int security_settime(struct timespec *ts, struct timezone *tz);
int security_vm_enough_memory(long pages);
int security_vm_enough_memory_mm(struct mm_struct *mm, long pages);
+int security_vm_enough_memory_kern(long pages);
int security_bprm_alloc(struct linux_binprm *bprm);
void security_bprm_free(struct linux_binprm *bprm);
void security_bprm_apply_creds(struct linux_binprm *bprm, int unsafe);
@@ -1820,6 +1821,11 @@ static inline int security_vm_enough_memory(long pages)
return cap_vm_enough_memory(current->mm, pages);
}
+static inline int security_vm_enough_memory_kern(long pages)
+{
+ return cap_vm_enough_memory(current->mm, pages);
+}
+
static inline int security_vm_enough_memory_mm(struct mm_struct *mm, long pages)
{
return cap_vm_enough_memory(mm, pages);
diff --git a/mm/mmap.c b/mm/mmap.c
index 74f4d158022ec..de14ac21e5b55 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -175,7 +175,8 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
/* Don't let a single process grow too big:
leave 3% of the size of this process for other processes */
- allowed -= mm->total_vm / 32;
+ if (mm)
+ allowed -= mm->total_vm / 32;
/*
* cast `allowed' as a signed long because vm_committed_space
diff --git a/mm/nommu.c b/mm/nommu.c
index 2696b24f2bb37..7695dc850785e 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1454,7 +1454,8 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
/* Don't let a single process grow too big:
leave 3% of the size of this process for other processes */
- allowed -= current->mm->total_vm / 32;
+ if (mm)
+ allowed -= mm->total_vm / 32;
/*
* cast `allowed' as a signed long because vm_committed_space
diff --git a/mm/shmem.c b/mm/shmem.c
index d38d7e61fcd0b..0ed075215e5f6 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -161,8 +161,8 @@ static inline struct shmem_sb_info *SHMEM_SB(struct super_block *sb)
*/
static inline int shmem_acct_size(unsigned long flags, loff_t size)
{
- return (flags & VM_ACCOUNT)?
- security_vm_enough_memory(VM_ACCT(size)): 0;
+ return (flags & VM_ACCOUNT) ?
+ security_vm_enough_memory_kern(VM_ACCT(size)) : 0;
}
static inline void shmem_unacct_size(unsigned long flags, loff_t size)
@@ -179,8 +179,8 @@ static inline void shmem_unacct_size(unsigned long flags, loff_t size)
*/
static inline int shmem_acct_block(unsigned long flags)
{
- return (flags & VM_ACCOUNT)?
- 0: security_vm_enough_memory(VM_ACCT(PAGE_CACHE_SIZE));
+ return (flags & VM_ACCOUNT) ?
+ 0 : security_vm_enough_memory_kern(VM_ACCT(PAGE_CACHE_SIZE));
}
static inline void shmem_unacct_blocks(unsigned long flags, long pages)
diff --git a/security/security.c b/security/security.c
index 255b08559b2b6..c0acfa7177e5d 100644
--- a/security/security.c
+++ b/security/security.c
@@ -198,14 +198,23 @@ int security_settime(struct timespec *ts, struct timezone *tz)
int security_vm_enough_memory(long pages)
{
+ WARN_ON(current->mm == NULL);
return security_ops->vm_enough_memory(current->mm, pages);
}
int security_vm_enough_memory_mm(struct mm_struct *mm, long pages)
{
+ WARN_ON(mm == NULL);
return security_ops->vm_enough_memory(mm, pages);
}
+int security_vm_enough_memory_kern(long pages)
+{
+ /* If current->mm is a kernel thread then we will pass NULL,
+ for this specific case that is fine */
+ return security_ops->vm_enough_memory(current->mm, pages);
+}
+
int security_bprm_alloc(struct linux_binprm *bprm)
{
return security_ops->bprm_alloc_security(bprm);