linux-toradex.git/mm/shmem.c, branch v4.2.3

ipc: use private shmem or hugetlbfs inodes for shm segments.

2015-08-07T01:39:41+00:00

The shm implementation internally uses shmem or hugetlbfs inodes for shm
segments.  As these inodes are never directly exposed to userspace and
only accessed through the shm operations which are already hooked by
security modules, mark the inodes with the S_PRIVATE flag so that inode
security initialization and permission checking is skipped.

This was motivated by the following lockdep warning:

  ======================================================
   [ INFO: possible circular locking dependency detected ]
   4.2.0-0.rc3.git0.1.fc24.x86_64+debug #1 Tainted: G        W
  -------------------------------------------------------
   httpd/1597 is trying to acquire lock:
   (&ids->rwsem){+++++.}, at: shm_close+0x34/0x130
   but task is already holding lock:
   (&mm->mmap_sem){++++++}, at: SyS_shmdt+0x4b/0x180
   which lock already depends on the new lock.
   the existing dependency chain (in reverse order) is:
   -> #3 (&mm->mmap_sem){++++++}:
        lock_acquire+0xc7/0x270
        __might_fault+0x7a/0xa0
        filldir+0x9e/0x130
        xfs_dir2_block_getdents.isra.12+0x198/0x1c0 [xfs]
        xfs_readdir+0x1b4/0x330 [xfs]
        xfs_file_readdir+0x2b/0x30 [xfs]
        iterate_dir+0x97/0x130
        SyS_getdents+0x91/0x120
        entry_SYSCALL_64_fastpath+0x12/0x76
   -> #2 (&xfs_dir_ilock_class){++++.+}:
        lock_acquire+0xc7/0x270
        down_read_nested+0x57/0xa0
        xfs_ilock+0x167/0x350 [xfs]
        xfs_ilock_attr_map_shared+0x38/0x50 [xfs]
        xfs_attr_get+0xbd/0x190 [xfs]
        xfs_xattr_get+0x3d/0x70 [xfs]
        generic_getxattr+0x4f/0x70
        inode_doinit_with_dentry+0x162/0x670
        sb_finish_set_opts+0xd9/0x230
        selinux_set_mnt_opts+0x35c/0x660
        superblock_doinit+0x77/0xf0
        delayed_superblock_init+0x10/0x20
        iterate_supers+0xb3/0x110
        selinux_complete_init+0x2f/0x40
        security_load_policy+0x103/0x600
        sel_write_load+0xc1/0x750
        __vfs_write+0x37/0x100
        vfs_write+0xa9/0x1a0
        SyS_write+0x58/0xd0
        entry_SYSCALL_64_fastpath+0x12/0x76
  ...

Signed-off-by: Stephen Smalley 
Reported-by: Morten Stevens 
Acked-by: Hugh Dickins 
Acked-by: Paul Moore 
Cc: Manfred Spraul 
Cc: Davidlohr Bueso 
Cc: Prarit Bhargava 
Cc: Eric Paris 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tmpfs: truncate prealloc blocks past i_size

2015-06-25T00:49:45+00:00

One of the rocksdb people noticed that when you do something like this

    fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, 10M)
    pwrite(fd, buf, 5M, 0)
    ftruncate(5M)

on tmpfs, the file would still take up 10M: which led to super fun
issues because we were getting ENOSPC before we thought we should be
getting ENOSPC.  This patch fixes the problem, and mirrors what all the
other fs'es do (and was agreed to be the correct behaviour at LSF).

I tested it locally to make sure it worked properly with the following

    xfs_io -f -c "falloc -k 0 10M" -c "pwrite 0 5M" -c "truncate 5M" file

Without the patch we have "Blocks: 20480", with the patch we have the
correct value of "Blocks: 10240".

Signed-off-by: Josef Bacik 
Signed-off-by: Hugh Dickins 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'for-linus-1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2015-06-22T19:51:21+00:00

Pull vfs updates from Al Viro:
 "In this pile: pathname resolution rewrite.

   - recursion in link_path_walk() is gone.

   - nesting limits on symlinks are gone (the only limit remaining is
     that the total amount of symlinks is no more than 40, no matter how
     nested).

   - "fast" (inline) symlinks are handled without leaving rcuwalk mode.

   - stack footprint (independent of the nesting) is below kilobyte now,
     about on par with what it used to be with one level of nested
     symlinks and ~2.8 times lower than it used to be in the worst case.

   - struct nameidata is entirely private to fs/namei.c now (not even
     opaque pointers are being passed around).

   - ->follow_link() and ->put_link() calling conventions had been
     changed; all in-tree filesystems converted, out-of-tree should be
     able to follow reasonably easily.

     For out-of-tree conversions, see Documentation/filesystems/porting
     for details (and in-tree filesystems for examples of conversion).

  That has sat in -next since mid-May, seems to survive all testing
  without regressions and merges clean with v4.1"

* 'for-linus-1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (131 commits)
  turn user_{path_at,path,lpath,path_dir}() into static inlines
  namei: move saved_nd pointer into struct nameidata
  inline user_path_create()
  inline user_path_parent()
  namei: trim do_last() arguments
  namei: stash dfd and name into nameidata
  namei: fold path_cleanup() into terminate_walk()
  namei: saner calling conventions for filename_parentat()
  namei: saner calling conventions for filename_create()
  namei: shift nameidata down into filename_parentat()
  namei: make filename_lookup() reject ERR_PTR() passed as name
  namei: shift nameidata inside filename_lookup()
  namei: move putname() call into filename_lookup()
  namei: pass the struct path to store the result down into path_lookupat()
  namei: uninline set_root{,_rcu}()
  namei: be careful with mountpoint crossings in follow_dotdot_rcu()
  Documentation: remove outdated information from automount-support.txt
  get rid of assorted nameidata-related debris
  lustre: kill unused helper
  lustre: kill unused macro (LOOKUP_CONTINUE)
  ...

mm: shmem_zero_setup skip security check and lockdep conflict with XFS

2015-06-18T06:40:19+00:00

It appears that, at some point last year, XFS made directory handling
changes which bring it into lockdep conflict with shmem_zero_setup():
it is surprising that mmap() can clone an inode while holding mmap_sem,
but that has been so for many years.

Since those few lockdep traces that I've seen all implicated selinux,
I'm hoping that we can use the __shmem_file_setup(,,,S_PRIVATE) which
v3.13's commit c7277090927a ("security: shmem: implement kernel private
shmem inodes") introduced to avoid LSM checks on kernel-internal inodes:
the mmap("/dev/zero") cloned inode is indeed a kernel-internal detail.

This also covers the !CONFIG_SHMEM use of ramfs to support /dev/zero
(and MAP_SHARED|MAP_ANONYMOUS).  I thought there were also drivers
which cloned inode in mmap(), but if so, I cannot locate them now.

Reported-and-tested-by: Prarit Bhargava 
Reported-and-tested-by: Daniel Wagner 
Reported-and-tested-by: Morten Stevens 
Signed-off-by: Hugh Dickins 
Signed-off-by: Linus Torvalds

switch ->put_link() from dentry to inode

2015-05-11T12:13:12+00:00

only one instance looks at that argument at all; that sole
exception wants inode rather than dentry.

Signed-off-by: Al Viro

don't pass nameidata to ->follow_link()

2015-05-11T02:20:15+00:00

its only use is getting passed to nd_jump_link(), which can obtain
it from current->nameidata

Signed-off-by: Al Viro

new ->follow_link() and ->put_link() calling conventions

2015-05-11T02:19:45+00:00

a) instead of storing the symlink body (via nd_set_link()) and returning
an opaque pointer later passed to ->put_link(), ->follow_link() _stores_
that opaque pointer (into void * passed by address by caller) and returns
the symlink body.  Returning ERR_PTR() on error, NULL on jump (procfs magic
symlinks) and pointer to symlink body for normal symlinks.  Stored pointer
is ignored in all cases except the last one.

Storing NULL for opaque pointer (or not storing it at all) means no call
of ->put_link().

b) the body used to be passed to ->put_link() implicitly (via nameidata).
Now only the opaque pointer is.  In the cases when we used the symlink body
to free stuff, ->follow_link() now should store it as opaque pointer in addition
to returning it.

Signed-off-by: Al Viro

shmem: switch to simple_follow_link()

2015-05-11T02:18:24+00:00

Reviewed-by: Jan Kara 
Signed-off-by: Al Viro

VFS: assorted weird filesystems: d_inode() annotations

2015-04-15T19:06:58+00:00

Signed-off-by: David Howells 
Signed-off-by: Al Viro

make new_sync_{read,write}() static

2015-04-12T02:29:40+00:00

All places outside of core VFS that checked ->read and ->write for being NULL or
called the methods directly are gone now, so NULL {read,write} with non-NULL
{read,write}_iter will do the right thing in all cases.

Signed-off-by: Al Viro