linux-stable.git/fs, branch v4.19.63

access: avoid the RCU grace period for the temporary subjective credentials

2019-07-31T05:27:11+00:00

commit d7852fbd0f0423937fa287a598bfde188bb68c22 upstream.

It turns out that 'access()' (and 'faccessat()') can cause a lot of RCU
work because it installs a temporary credential that gets allocated and
freed for each system call.

The allocation and freeing overhead is mostly benign, but because
credentials can be accessed under the RCU read lock, the freeing
involves a RCU grace period.

Which is not a huge deal normally, but if you have a lot of access()
calls, this causes a fair amount of seconday damage: instead of having a
nice alloc/free patterns that hits in hot per-CPU slab caches, you have
all those delayed free's, and on big machines with hundreds of cores,
the RCU overhead can end up being enormous.

But it turns out that all of this is entirely unnecessary.  Exactly
because access() only installs the credential as the thread-local
subjective credential, the temporary cred pointer doesn't actually need
to be RCU free'd at all.  Once we're done using it, we can just free it
synchronously and avoid all the RCU overhead.

So add a 'non_rcu' flag to 'struct cred', which can be set by users that
know they only use it in non-RCU context (there are other potential
users for this).  We can make it a union with the rcu freeing list head
that we need for the RCU case, so this doesn't need any extra storage.

Note that this also makes 'get_current_cred()' clear the new non_rcu
flag, in case we have filesystems that take a long-term reference to the
cred and then expect the RCU delayed freeing afterwards.  It's not
entirely clear that this is required, but it makes for clear semantics:
the subjective cred remains non-RCU as long as you only access it
synchronously using the thread-local accessors, but you _can_ use it as
a generic cred if you want to.

It is possible that we should just remove the whole RCU markings for
->cred entirely.  Only ->real_cred is really supposed to be accessed
through RCU, and the long-term cred copies that nfs uses might want to
explicitly re-enable RCU freeing if required, rather than have
get_current_cred() do it implicitly.

But this is a "minimal semantic changes" change for the immediate
problem.

Acked-by: Peter Zijlstra (Intel) 
Acked-by: Eric Dumazet 
Acked-by: Paul E. McKenney 
Cc: Oleg Nesterov 
Cc: Jan Glauber 
Cc: Jiri Kosina 
Cc: Jayachandran Chandrasekharan Nair 
Cc: Greg KH 
Cc: Kees Cook 
Cc: David Howells 
Cc: Miklos Szeredi 
Cc: Al Viro 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

btrfs: inode: Don't compress if NODATASUM or NODATACOW set

2019-07-31T05:27:10+00:00

commit 42c16da6d684391db83788eb680accd84f6c2083 upstream.

As btrfs(5) specified:

	Note
	If nodatacow or nodatasum are enabled, compression is disabled.

If NODATASUM or NODATACOW set, we should not compress the extent.

Normally NODATACOW is detected properly in run_delalloc_range() so
compression won't happen for NODATACOW.

However for NODATASUM we don't have any check, and it can cause
compressed extent without csum pretty easily, just by:
  mkfs.btrfs -f $dev
  mount $dev $mnt -o nodatasum
  touch $mnt/foobar
  mount -o remount,datasum,compress $mnt
  xfs_io -f -c "pwrite 0 128K" $mnt/foobar

And in fact, we have a bug report about corrupted compressed extent
without proper data checksum so even RAID1 can't recover the corruption.
(https://bugzilla.kernel.org/show_bug.cgi?id=199707)

Running compression without proper checksum could cause more damage when
corruption happens, as compressed data could make the whole extent
unreadable, so there is no need to allow compression for
NODATACSUM.

The fix will refactor the inode compression check into two parts:

- inode_can_compress()
  As the hard requirement, checked at btrfs_run_delalloc_range(), so no
  compression will happen for NODATASUM inode at all.

- inode_need_compress()
  As the soft requirement, checked at btrfs_run_delalloc_range() and
  compress_file_range().

Reported-by: James Harvey 
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Qu Wenruo 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba 
Signed-off-by: Greg Kroah-Hartman

proc: use down_read_killable mmap_sem for /proc/pid/maps

2019-07-31T05:27:09+00:00

[ Upstream commit 8a713e7df3352b8d9392476e9cf29e4e185dac32 ]

Do not remain stuck forever if something goes wrong.  Using a killable
lock permits cleanup of stuck tasks and simplifies investigation.

This function is also used for /proc/pid/smaps.

Link: http://lkml.kernel.org/r/156007493160.3335.14447544314127417266.stgit@buzz
Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Roman Gushchin 
Reviewed-by: Cyrill Gorcunov 
Reviewed-by: Kirill Tkhai 
Acked-by: Michal Hocko 
Cc: Alexey Dobriyan 
Cc: Al Viro 
Cc: Matthew Wilcox 
Cc: Michal Koutný 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

proc: use down_read_killable mmap_sem for /proc/pid/map_files

2019-07-31T05:27:09+00:00

[ Upstream commit cd9e2bb8271c971d9f37c722be2616c7f8ba0664 ]

Do not remain stuck forever if something goes wrong.  Using a killable
lock permits cleanup of stuck tasks and simplifies investigation.

It seems ->d_revalidate() could return any error (except ECHILD) to abort
validation and pass error as result of lookup sequence.

[akpm@linux-foundation.org: fix proc_map_files_lookup() return value, per Andrei]
Link: http://lkml.kernel.org/r/156007493995.3335.9595044802115356911.stgit@buzz
Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Roman Gushchin 
Reviewed-by: Cyrill Gorcunov 
Reviewed-by: Kirill Tkhai 
Acked-by: Michal Hocko 
Cc: Alexey Dobriyan 
Cc: Al Viro 
Cc: Matthew Wilcox 
Cc: Michal Koutný 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

proc: use down_read_killable mmap_sem for /proc/pid/clear_refs

2019-07-31T05:27:09+00:00

[ Upstream commit c46038017fbdcac627b670c9d4176f1d0c2f5fa3 ]

Do not remain stuck forever if something goes wrong.  Using a killable
lock permits cleanup of stuck tasks and simplifies investigation.

Replace the only unkillable mmap_sem lock in clear_refs_write().

Link: http://lkml.kernel.org/r/156007493826.3335.5424884725467456239.stgit@buzz
Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Roman Gushchin 
Reviewed-by: Cyrill Gorcunov 
Reviewed-by: Kirill Tkhai 
Acked-by: Michal Hocko 
Cc: Alexey Dobriyan 
Cc: Al Viro 
Cc: Matthew Wilcox 
Cc: Michal Koutný 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

proc: use down_read_killable mmap_sem for /proc/pid/pagemap

2019-07-31T05:27:09+00:00

[ Upstream commit ad80b932c57d85fd6377f97f359b025baf179a87 ]

Do not remain stuck forever if something goes wrong.  Using a killable
lock permits cleanup of stuck tasks and simplifies investigation.

Link: http://lkml.kernel.org/r/156007493638.3335.4872164955523928492.stgit@buzz
Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Roman Gushchin 
Reviewed-by: Cyrill Gorcunov 
Reviewed-by: Kirill Tkhai 
Acked-by: Michal Hocko 
Cc: Alexey Dobriyan 
Cc: Al Viro 
Cc: Matthew Wilcox 
Cc: Michal Koutný 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

proc: use down_read_killable mmap_sem for /proc/pid/smaps_rollup

2019-07-31T05:27:08+00:00

[ Upstream commit a26a97815548574213fd37f29b4b78ccc6d9ed20 ]

Do not remain stuck forever if something goes wrong.  Using a killable
lock permits cleanup of stuck tasks and simplifies investigation.

Link: http://lkml.kernel.org/r/156007493429.3335.14666825072272692455.stgit@buzz
Signed-off-by: Konstantin Khlebnikov 
Reviewed-by: Roman Gushchin 
Reviewed-by: Cyrill Gorcunov 
Reviewed-by: Kirill Tkhai 
Acked-by: Michal Hocko 
Cc: Alexey Dobriyan 
Cc: Al Viro 
Cc: Matthew Wilcox 
Cc: Michal Koutný 
Cc: Oleg Nesterov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

memcg, fsnotify: no oom-kill for remote memcg charging

2019-07-31T05:27:08+00:00

[ Upstream commit ec165450968b26298bd1c373de37b0ab6d826b33 ]

Commit d46eb14b735b ("fs: fsnotify: account fsnotify metadata to
kmemcg") added remote memcg charging for fanotify and inotify event
objects.  The aim was to charge the memory to the listener who is
interested in the events but without triggering the OOM killer.
Otherwise there would be security concerns for the listener.

At the time, oom-kill trigger was not in the charging path.  A parallel
work added the oom-kill back to charging path i.e.  commit 29ef680ae7c2
("memcg, oom: move out_of_memory back to the charge path").  So to not
trigger oom-killer in the remote memcg, explicitly add
__GFP_RETRY_MAYFAIL to the fanotigy and inotify event allocations.

Link: http://lkml.kernel.org/r/20190514212259.156585-2-shakeelb@google.com
Signed-off-by: Shakeel Butt 
Reviewed-by: Roman Gushchin 
Acked-by: Jan Kara 
Cc: Johannes Weiner 
Cc: Vladimir Davydov 
Cc: Michal Hocko 
Cc: Amir Goldstein 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

9p: pass the correct prototype to read_cache_page

2019-07-31T05:27:08+00:00

[ Upstream commit f053cbd4366051d7eb6ba1b8d529d20f719c2963 ]

Fix the callback 9p passes to read_cache_page to actually have the
proper type expected.  Casting around function pointers can easily
hide typing bugs, and defeats control flow protection.

Link: http://lkml.kernel.org/r/20190520055731.24538-5-hch@lst.de
Signed-off-by: Christoph Hellwig 
Reviewed-by: Kees Cook 
Cc: Sami Tolvanen 
Cc: Nick Desaulniers 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

dlm: check if workqueues are NULL before flushing/destroying

2019-07-31T05:27:07+00:00

[ Upstream commit b355516f450703c9015316e429b66a93dfff0e6f ]

If the DLM lowcomms stack is shut down before any DLM
traffic can be generated, flush_workqueue() and
destroy_workqueue() can be called on empty send and/or recv
workqueues.

Insert guard conditionals to only call flush_workqueue()
and destroy_workqueue() on workqueues that are not NULL.

Signed-off-by: David Windsor 
Signed-off-by: David Teigland 
Signed-off-by: Sasha Levin