Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752314AbYJ0O1p (ORCPT ); Mon, 27 Oct 2008 10:27:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751210AbYJ0O1Y (ORCPT ); Mon, 27 Oct 2008 10:27:24 -0400 Received: from earthlight.etchedpixels.co.uk ([81.2.110.250]:56220 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751150AbYJ0O1X (ORCPT ); Mon, 27 Oct 2008 10:27:23 -0400 From: Alan Cox Subject: [PATCH] nfsd: Fix vm overcommit crash To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Date: Mon, 27 Oct 2008 14:27:28 +0000 Message-ID: <20081027142445.21908.74962.stgit@localhost.localdomain> User-Agent: StGIT/0.14.2 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4550 Lines: 122 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. While at it the checks are switched to WARN_ON - we need to know if someone gets current->mm wrong in the other calls but we don't need to crash. Also fix a current->mm reference in nommu that should use the passed mm Signed-off-by: Alan Cox --- include/linux/security.h | 1 + mm/mmap.c | 3 ++- mm/nommu.c | 3 ++- mm/shmem.c | 4 ++-- security/security.c | 9 +++++++++ 5 files changed, 16 insertions(+), 4 deletions(-) diff --git a/include/linux/security.h b/include/linux/security.h index f5c4a51..a2b8430 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); diff --git a/mm/mmap.c b/mm/mmap.c index 74f4d15..de14ac2 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 2696b24..7695dc8 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 d38d7e6..1677b3e 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -162,7 +162,7 @@ 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; + security_vm_enough_memory_kern(VM_ACCT(size)): 0; } static inline void shmem_unacct_size(unsigned long flags, loff_t size) @@ -180,7 +180,7 @@ 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)); + 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 255b085..c0acfa7 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/