lkml.org 
[lkml]   [2010]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    SubjectRe: TMPFS over NFSv4
    Hi Greg,

    On Mon, 24 May 2010, Alan Cox wrote:
    > On Mon, 24 May 2010 02:57:30 -0700
    > Hugh Dickins <hughd@google.com> wrote:
    > > On Mon, May 24, 2010 at 2:26 AM, Tharindu Rukshan Bamunuarachchi
    > > <btharindu@gmail.com> wrote:
    > > > thankx a lot Hugh ... I will try this out ... (bit harder patch
    > > > already patched SLES kernel :-p ) ....
    > >
    > > If patch conflicts are a problem, you really only need to put in the
    > > two-liner patch to mm/mmap.c: Alan was seeking perfection in
    > > the rest of the patch, but you can get away without it.
    > >
    > > >
    > > > BTW, what does Alan means by "strict overcommit" ?
    > >
    > > Ah, that phrase, yes, it's a nonsense, but many of us do say it by mistake.
    > > Alan meant to say "strict no-overcommit".
    >
    > No I always meant to say 'strict overcommit'. It avoids excess negatives
    > and "no noovercommit" discussions.
    >
    > I guess 'strict overcommit control' would have been clearer 8)
    >
    > Alan

    I see we've just missed 2.6.27.47-rc1, but if there's to be an -rc2,
    please include Alan's 2.6.28 oops fix below: which Tharindu appears
    to be needing - just now discussed on linux-mm and linux-nfs.
    Failing that, please queue it up for 2.6.27.48.

    Or if you'd prefer a smaller patch for -stable, then just the mm/mmap.c
    part of it should suffice: I think it's fair to say that the rest of the
    patch was more precautionary - as Alan describes, for catching other bugs,
    so good for an ongoing development tree, but not necessarily in -stable.
    (However, Alan may disagree - I've already misrepresented him once here!)

    Thanks,
    Hugh

    commit 731572d39fcd3498702eda4600db4c43d51e0b26
    Author: Alan Cox <alan@redhat.com>
    Date: Wed Oct 29 14:01:20 2008 -0700

    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>

    diff --git a/include/linux/security.h b/include/linux/security.h
    index f5c4a51..c13f1ce 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 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..0ed0752 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 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);

    \
     
     \ /
      Last update: 2010-05-25 01:49    [W:0.029 / U:0.656 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site