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Commit 731572d3 authored by Alan Cox's avatar Alan Cox Committed by Linus Torvalds
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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: default avatarJunjiro R. Okajima <hooanon05@yahoo.co.jp>
Acked-by: default avatarJames Morris <jmorris@namei.org>
Signed-off-by: default avatarAlan Cox <alan@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6c89161b

include/linux/security.h

+6 −0
Original line number Diff line number Diff line
@@ -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);

mm/mmap.c

+2 −1
Original line number Diff line number Diff line
@@ -175,6 +175,7 @@ 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 */

	if (mm)

		allowed -= mm->total_vm / 32;



	/*

mm/nommu.c

+2 −1
Original line number Diff line number Diff line
@@ -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

mm/shmem.c

+4 −4
Original line number Diff line number Diff line
@@ -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)

security/security.c

+9 −0
Original line number Diff line number Diff line
@@ -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);