Messages in this thread | | | Date | Thu, 23 Oct 2008 00:37:02 +1100 (EST) | From | James Morris <> | Subject | Re: __vm_enough_memory(), OVERCOMMIT_NEVER, current->mm, kernel thread |
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On Wed, 22 Oct 2008, Alan Cox wrote:
[Adding lsm list to the cc]
> On Wed, 22 Oct 2008 20:26:19 +0900 > hooanon05@yahoo.co.jp wrote: > > > > > Alan Cox: > > > No - the shmem routine would use vm_enough_memory_fs which wouldn't care > > > if current->mm is NULL, but the others would check. > > > > Unfortunately I cannot imagine what new vm_enough_memory_fs() will be. > > Would you show me its draft or pseudo code? > > This is the patch I propose: > > nfsd: Fix vm overcommit crash > > From: Alan Cox <alan@redhat.com> > > 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
Looks ok to me.
Acked-by: James Morris <jmorris@namei.org>
> --- > > 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/ >
-- James Morris <jmorris@namei.org>
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