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nfsd: fix vm overcommit crash

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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>
This commit is contained in:
Alan Cox
2008-10-29 14:01:20 -07:00
committed by Linus Torvalds
parent 6c89161b10
commit 731572d39f
5 changed files with 23 additions and 6 deletions
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8
mm/shmem.c
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@@ -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)