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  1. 30 3月, 2018 9 次提交
  3. 12 3月, 2018 4 次提交
  5. 26 2月, 2018 2 次提交
  7. 24 2月, 2018 1 次提交
    • A
      lock_parent() needs to recheck if dentry got __dentry_kill'ed under it · 3b821409
      由 Al Viro 提交于 
      In case when dentry passed to lock_parent() is protected from freeing only
by the fact that it's on a shrink list and trylock of parent fails, we
could get hit by __dentry_kill() (and subsequent dentry_kill(parent))
between unlocking dentry and locking presumed parent.  We need to recheck
that dentry is alive once we lock both it and parent *and* postpone
rcu_read_unlock() until after that point.  Otherwise we could return
a pointer to struct dentry that already is rcu-scheduled for freeing, with
->d_lock held on it; caller's subsequent attempt to unlock it can end
up with memory corruption.

Cc: stable@vger.kernel.org # 3.12+, counting backports
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      3b821409
  9. 02 2月, 2018 2 次提交
  11. 26 1月, 2018 2 次提交
  13. 24 1月, 2018 2 次提交
  15. 16 1月, 2018 2 次提交
    • D
      vfs: Define usercopy region in names_cache slab caches · 6a9b8820
      由 David Windsor 提交于 
      VFS pathnames are stored in the names_cache slab cache, either inline
or across an entire allocation entry (when approaching PATH_MAX). These
are copied to/from userspace, so they must be entirely whitelisted.

cache object allocation:
    include/linux/fs.h:
        #define __getname()    kmem_cache_alloc(names_cachep, GFP_KERNEL)

example usage trace:
    strncpy_from_user+0x4d/0x170
    getname_flags+0x6f/0x1f0
    user_path_at_empty+0x23/0x40
    do_mount+0x69/0xda0
    SyS_mount+0x83/0xd0

    fs/namei.c:
        getname_flags(...):
            ...
            result = __getname();
            ...
            kname = (char *)result->iname;
            result->name = kname;
            len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
            ...
            if (unlikely(len == EMBEDDED_NAME_MAX)) {
                const size_t size = offsetof(struct filename, iname[1]);
                kname = (char *)result;

                result = kzalloc(size, GFP_KERNEL);
                ...
                result->name = kname;
                len = strncpy_from_user(kname, filename, PATH_MAX);

In support of usercopy hardening, this patch defines the entire cache
object in the names_cache slab cache as whitelisted, since it may entirely
hold name strings to be copied to/from userspace.

This patch is verbatim from Brad Spengler/PaX Team's PAX_USERCOPY
whitelisting code in the last public patch of grsecurity/PaX based on my
understanding of the code. Changes or omissions from the original code are
mine and don't reflect the original grsecurity/PaX code.
Signed-off-by: NDavid Windsor <dave@nullcore.net>
[kees: adjust commit log, add usage trace]
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: NKees Cook <keescook@chromium.org>
      6a9b8820
    • D
      dcache: Define usercopy region in dentry_cache slab cache · 80344266
      由 David Windsor 提交于 
      When a dentry name is short enough, it can be stored directly in the
dentry itself (instead in a separate kmalloc allocation). These dentry
short names, stored in struct dentry.d_iname and therefore contained in
the dentry_cache slab cache, need to be coped to userspace.

cache object allocation:
    fs/dcache.c:
        __d_alloc(...):
            ...
            dentry = kmem_cache_alloc(dentry_cache, ...);
            ...
            dentry->d_name.name = dentry->d_iname;

example usage trace:
    filldir+0xb0/0x140
    dcache_readdir+0x82/0x170
    iterate_dir+0x142/0x1b0
    SyS_getdents+0xb5/0x160

    fs/readdir.c:
        (called via ctx.actor by dir_emit)
        filldir(..., const char *name, ...):
            ...
            copy_to_user(..., name, namlen)

    fs/libfs.c:
        dcache_readdir(...):
            ...
            next = next_positive(dentry, p, 1)
            ...
            dir_emit(..., next->d_name.name, ...)

In support of usercopy hardening, this patch defines a region in the
dentry_cache slab cache in which userspace copy operations are allowed.

This region is known as the slab cache's usercopy region. Slab caches can
now check that each dynamic copy operation involving cache-managed memory
falls entirely within the slab's usercopy region.

This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY
whitelisting code in the last public patch of grsecurity/PaX based on my
understanding of the code. Changes or omissions from the original code are
mine and don't reflect the original grsecurity/PaX code.
Signed-off-by: NDavid Windsor <dave@nullcore.net>
[kees: adjust hunks for kmalloc-specific things moved later]
[kees: adjust commit log, provide usage trace]
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: NKees Cook <keescook@chromium.org>
      80344266
  17. 29 12月, 2017 1 次提交
    • N
      VFS: close race between getcwd() and d_move() · 61647823
      由 NeilBrown 提交于 
      d_move() will call __d_drop() and then __d_rehash()
on the dentry being moved.  This creates a small window
when the dentry appears to be unhashed.  Many tests
of d_unhashed() are made under ->d_lock and so are safe
from racing with this window, but some aren't.
In particular, getcwd() calls d_unlinked() (which calls
d_unhashed()) without d_lock protection, so it can race.

This races has been seen in practice with lustre, which uses d_move() as
part of name lookup.  See:
   https://jira.hpdd.intel.com/browse/LU-9735
It could race with a regular rename(), and result in ENOENT instead
of either the 'before' or 'after' name.

The race can be demonstrated with a simple program which
has two threads, one renaming a directory back and forth
while another calls getcwd() within that directory: it should never
fail, but does.  See:
  https://patchwork.kernel.org/patch/9455345/

We could fix this race by taking d_lock and rechecking when
d_unhashed() reports true.  Alternately when can remove the window,
which is the approach this patch takes.

___d_drop() is introduce which does *not* clear d_hash.pprev
so the dentry still appears to be hashed.  __d_drop() calls
___d_drop(), then clears d_hash.pprev.
__d_move() now uses ___d_drop() and only clears d_hash.pprev
when not rehashing.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      61647823
  19. 26 12月, 2017 1 次提交
    • N
      VFS: don't keep disconnected dentries on d_anon · f1ee6162
      由 NeilBrown 提交于 
      The original purpose of the per-superblock d_anon list was to
keep disconnected dentries in the cache between consecutive
requests to the NFS server.  Dentries can be disconnected if
a client holds a file open and repeatedly performs IO on it,
and if the server drops the dentry, whether due to memory
pressure, server restart, or "echo 3 > /proc/sys/vm/drop_caches".

This purpose was thwarted by commit 75a6f82a ("freeing unlinked
file indefinitely delayed") which caused disconnected dentries
to be freed as soon as their refcount reached zero.

This means that, when a dentry being used by nfsd gets disconnected, a
new one needs to be allocated for every request (unless requests
overlap).  As the dentry has no name, no parent, and no children,
there is little of value to cache.  As small memory allocations are
typically fast (from per-cpu free lists) this likely has little cost.

This means that the original purpose of s_anon is no longer relevant:
there is no longer any need to keep disconnected dentries on a list so
they appear to be hashed.

However, s_anon now has a new use.  When you mount an NFS filesystem,
the dentry stored in s_root is just a placebo.  The "real" root dentry
is allocated using d_obtain_root() and so it kept on the s_anon list.
I don't know the reason for this, but suspect it related to NFSv4
where a mount of "server:/some/path" require NFS to look up the root
filehandle on the server, then walk down "/some" and "/path" to get
the filehandle to mount.

Whatever the reason, NFS depends on the s_anon list and on
shrink_dcache_for_umount() pruning all dentries on this list.  So we
cannot simply remove s_anon.

We could just leave the code unchanged, but apart from that being
potentially confusing, the (unfair) bit-spin-lock which protects
s_anon can become a bottle neck when lots of disconnected dentries are
being created.

So this patch renames s_anon to s_roots, and stops storing
disconnected dentries on the list.  Only dentries obtained with
d_obtain_root() are now stored on this list.  There are many fewer of
these (only NFS and NILFS2 use the call, and only during filesystem
mount) so contention on the bit-lock will not be a problem.

Possibly an alternate solution should be found for NFS and NILFS2, but
that would require understanding their needs first.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      f1ee6162
  21. 17 12月, 2017 1 次提交
  23. 08 12月, 2017 1 次提交
  25. 05 12月, 2017 1 次提交
    • P
      fs/dcache: Use release-acquire for name/length update · 7088efa9
      由 Paul E. McKenney 提交于 
      The code in __d_alloc() carefully orders filling in the NUL character
of the name (and the length, hash, and the name itself) with assigning
of the name itself.  However, prepend_name() does not order the accesses
to the ->name and ->len fields, other than on TSO systems.  This commit
therefore replaces prepend_name()'s READ_ONCE() of ->name with an
smp_load_acquire(), which orders against the subsequent READ_ONCE() of
->len.  Because READ_ONCE() now incorporates smp_read_barrier_depends(),
prepend_name()'s smp_read_barrier_depends() is removed.  Finally,
to save a line, the smp_wmb()/store pair in __d_alloc() is replaced
by smp_store_release().
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <linux-fsdevel@vger.kernel.org>
      7088efa9
  27. 16 11月, 2017 1 次提交
  29. 25 10月, 2017 1 次提交
    • M
      locking/atomics, fs/dcache: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE() · 66702eb5
      由 Mark Rutland 提交于 
      For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.

However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.

It's possible to transform the bulk of kernel code using the Coccinelle
script below. However, this doesn't handle comments, leaving references
to ACCESS_ONCE() instances which have been removed. As a preparatory
step, this patch converts the dcache code and comments to use
{READ,WRITE}_ONCE() consistently.

----
virtual patch

@ depends on patch @
expression E1, E2;
@@

- ACCESS_ONCE(E1) = E2
+ WRITE_ONCE(E1, E2)

@ depends on patch @
expression E;
@@

- ACCESS_ONCE(E)
+ READ_ONCE(E)
----
Signed-off-by: NMark Rutland <mark.rutland@arm.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: mpe@ellerman.id.au
Cc: shuah@kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-4-git-send-email-paulmck@linux.vnet.ibm.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      66702eb5
  31. 24 10月, 2017 1 次提交
  33. 11 7月, 2017 1 次提交
  35. 08 7月, 2017 1 次提交
    • A
      dentry name snapshots · 49d31c2f
      由 Al Viro 提交于 
      take_dentry_name_snapshot() takes a safe snapshot of dentry name;
if the name is a short one, it gets copied into caller-supplied
structure, otherwise an extra reference to external name is grabbed
(those are never modified).  In either case the pointer to stable
string is stored into the same structure.

dentry must be held by the caller of take_dentry_name_snapshot(),
but may be freely dropped afterwards - the snapshot will stay
until destroyed by release_dentry_name_snapshot().

Intended use:
	struct name_snapshot s;

	take_dentry_name_snapshot(&s, dentry);
	...
	access s.name
	...
	release_dentry_name_snapshot(&s);

Replaces fsnotify_oldname_...(), gets used in fsnotify to obtain the name
to pass down with event.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      49d31c2f
  37. 07 7月, 2017 1 次提交
    • P
      mm: update callers to use HASH_ZERO flag · 3d375d78
      由 Pavel Tatashin 提交于 
      Update dcache, inode, pid, mountpoint, and mount hash tables to use
HASH_ZERO, and remove initialization after allocations.  In case of
places where HASH_EARLY was used such as in __pv_init_lock_hash the
zeroed hash table was already assumed, because memblock zeroes the
memory.

CPU: SPARC M6, Memory: 7T
Before fix:
  Dentry cache hash table entries: 1073741824
  Inode-cache hash table entries: 536870912
  Mount-cache hash table entries: 16777216
  Mountpoint-cache hash table entries: 16777216
  ftrace: allocating 20414 entries in 40 pages
  Total time: 11.798s

After fix:
  Dentry cache hash table entries: 1073741824
  Inode-cache hash table entries: 536870912
  Mount-cache hash table entries: 16777216
  Mountpoint-cache hash table entries: 16777216
  ftrace: allocating 20414 entries in 40 pages
  Total time: 3.198s

CPU: Intel Xeon E5-2630, Memory: 2.2T:
Before fix:
  Dentry cache hash table entries: 536870912
  Inode-cache hash table entries: 268435456
  Mount-cache hash table entries: 8388608
  Mountpoint-cache hash table entries: 8388608
  CPU: Physical Processor ID: 0
  Total time: 3.245s

After fix:
  Dentry cache hash table entries: 536870912
  Inode-cache hash table entries: 268435456
  Mount-cache hash table entries: 8388608
  Mountpoint-cache hash table entries: 8388608
  CPU: Physical Processor ID: 0
  Total time: 3.244s

Link: http://lkml.kernel.org/r/1488432825-92126-4-git-send-email-pasha.tatashin@oracle.comSigned-off-by: NPavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: NBabu Moger <babu.moger@oracle.com>
Cc: David Miller <davem@davemloft.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3d375d78
  39. 06 7月, 2017 1 次提交
  41. 30 6月, 2017 1 次提交
  43. 15 6月, 2017 1 次提交
    • A
      Hang/soft lockup in d_invalidate with simultaneous calls · 81be24d2
      由 Al Viro 提交于 
      It's not hard to trigger a bunch of d_invalidate() on the same
dentry in parallel.  They end up fighting each other - any
dentry picked for removal by one will be skipped by the rest
and we'll go for the next iteration through the entire
subtree, even if everything is being skipped.  Morevoer, we
immediately go back to scanning the subtree.  The only thing
we really need is to dissolve all mounts in the subtree and
as soon as we've nothing left to do, we can just unhash the
dentry and bugger off.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      81be24d2
  45. 03 5月, 2017 1 次提交
    • J
      fs: don't set *REFERENCED on single use objects · 563f4001
      由 Josef Bacik 提交于 
      By default we set DCACHE_REFERENCED and I_REFERENCED on any dentry or
inode we create.  This is problematic as this means that it takes two
trips through the LRU for any of these objects to be reclaimed,
regardless of their actual lifetime.  With enough pressure from these
caches we can easily evict our working set from page cache with single
use objects.  So instead only set *REFERENCED if we've already been
added to the LRU list.  This means that we've been touched since the
first time we were accessed, and so more likely to need to hang out in
cache.

To illustrate this issue I wrote the following scripts

https://github.com/josefbacik/debug-scripts/tree/master/cache-pressure

on my test box.  It is a single socket 4 core CPU with 16gib of RAM and
I tested on an Intel 2tib NVME drive.  The cache-pressure.sh script
creates a new file system and creates 2 6.5gib files in order to take up
13gib of the 16gib of ram with pagecache.  Then it runs a test program
that reads these 2 files in a loop, and keeps track of how often it has
to read bytes for each loop.  On an ideal system with no pressure we
should have to read 0 bytes indefinitely.  The second thing this script
does is start a fs_mark job that creates a ton of 0 length files,
putting pressure on the system with slab only allocations.  On exit the
script prints out how many bytes were read by the read-file program.
The results are as follows

Without patch:
/mnt/btrfs-test/reads/file1: total read during loops 27262988288
/mnt/btrfs-test/reads/file2: total read during loops 27262976000

With patch:
/mnt/btrfs-test/reads/file2: total read during loops 18640457728
/mnt/btrfs-test/reads/file1: total read during loops 9565376512

This patch results in a 50% reduction of the amount of pages evicted
from our working set.
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
      563f4001
  47. 10 1月, 2017 1 次提交
    • E
      mnt: Protect the mountpoint hashtable with mount_lock · 3895dbf8
      由 Eric W. Biederman 提交于 
      Protecting the mountpoint hashtable with namespace_sem was sufficient
until a call to umount_mnt was added to mntput_no_expire.  At which
point it became possible for multiple calls of put_mountpoint on
the same hash chain to happen on the same time.

Kristen Johansen <kjlx@templeofstupid.com> reported:
> This can cause a panic when simultaneous callers of put_mountpoint
> attempt to free the same mountpoint.  This occurs because some callers
> hold the mount_hash_lock, while others hold the namespace lock.  Some
> even hold both.
>
> In this submitter's case, the panic manifested itself as a GP fault in
> put_mountpoint() when it called hlist_del() and attempted to dereference
> a m_hash.pprev that had been poisioned by another thread.

Al Viro observed that the simple fix is to switch from using the namespace_sem
to the mount_lock to protect the mountpoint hash table.

I have taken Al's suggested patch moved put_mountpoint in pivot_root
(instead of taking mount_lock an additional time), and have replaced
new_mountpoint with get_mountpoint a function that does the hash table
lookup and addition under the mount_lock.   The introduction of get_mounptoint
ensures that only the mount_lock is needed to manipulate the mountpoint
hashtable.

d_set_mounted is modified to only set DCACHE_MOUNTED if it is not
already set.  This allows get_mountpoint to use the setting of
DCACHE_MOUNTED to ensure adding a struct mountpoint for a dentry
happens exactly once.

Cc: stable@vger.kernel.org
Fixes: ce07d891 ("mnt: Honor MNT_LOCKED when detaching mounts")
Reported-by: NKrister Johansen <kjlx@templeofstupid.com>
Suggested-by: NAl Viro <viro@ZenIV.linux.org.uk>
Acked-by: NAl Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
      3895dbf8