linux-toradex.git/drivers/android/binder_alloc.c, branch v5.9-rc6

drivers: android: Fix a variable declaration coding style issue

2020-07-29T15:04:40+00:00

Add a blank line after variable declarations as suggested by checkpatch.

Signed-off-by: Mrinal Pandey 
Link: https://lore.kernel.org/r/20200724131254.qxbvderrws36dzzq@mrinalpandey
Signed-off-by: Greg Kroah-Hartman

binder: Don't use mmput() from shrinker function.

2020-07-23T07:47:12+00:00

syzbot is reporting that mmput() from shrinker function has a risk of
deadlock [1], for delayed_uprobe_add() from update_ref_ctr() calls
kzalloc(GFP_KERNEL) with delayed_uprobe_lock held, and
uprobe_clear_state() from __mmput() also holds delayed_uprobe_lock.

Commit a1b2289cef92ef0e ("android: binder: drop lru lock in isolate
callback") replaced mmput() with mmput_async() in order to avoid sleeping
with spinlock held. But this patch replaces mmput() with mmput_async() in
order not to start __mmput() from shrinker context.

[1] https://syzkaller.appspot.com/bug?id=bc9e7303f537c41b2b0cc2dfcea3fc42964c2d45

Reported-by: syzbot 
Reported-by: syzbot 
Signed-off-by: Tetsuo Handa 
Reviewed-by: Michal Hocko 
Acked-by: Todd Kjos 
Acked-by: Christian Brauner 
Cc: stable 
Link: https://lore.kernel.org/r/4ba9adb2-43f5-2de0-22de-f6075c1fab50@i-love.sakura.ne.jp
Signed-off-by: Greg Kroah-Hartman

mmap locking API: convert mmap_sem API comments

2020-06-09T16:39:14+00:00

Convert comments that reference old mmap_sem APIs to reference
corresponding new mmap locking APIs instead.

Signed-off-by: Michel Lespinasse 
Signed-off-by: Andrew Morton 
Reviewed-by: Vlastimil Babka 
Reviewed-by: Davidlohr Bueso 
Reviewed-by: Daniel Jordan 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Jason Gunthorpe 
Cc: Jerome Glisse 
Cc: John Hubbard 
Cc: Laurent Dufour 
Cc: Liam Howlett 
Cc: Matthew Wilcox 
Cc: Peter Zijlstra 
Cc: Ying Han 
Link: http://lkml.kernel.org/r/20200520052908.204642-12-walken@google.com
Signed-off-by: Linus Torvalds

mmap locking API: use coccinelle to convert mmap_sem rwsem call sites

2020-06-09T16:39:14+00:00

This change converts the existing mmap_sem rwsem calls to use the new mmap
locking API instead.

The change is generated using coccinelle with the following rule:

// spatch --sp-file mmap_lock_api.cocci --in-place --include-headers --dir .

@@
expression mm;
@@
(
-init_rwsem
+mmap_init_lock
|
-down_write
+mmap_write_lock
|
-down_write_killable
+mmap_write_lock_killable
|
-down_write_trylock
+mmap_write_trylock
|
-up_write
+mmap_write_unlock
|
-downgrade_write
+mmap_write_downgrade
|
-down_read
+mmap_read_lock
|
-down_read_killable
+mmap_read_lock_killable
|
-down_read_trylock
+mmap_read_trylock
|
-up_read
+mmap_read_unlock
)
-(&mm->mmap_sem)
+(mm)

Signed-off-by: Michel Lespinasse 
Signed-off-by: Andrew Morton 
Reviewed-by: Daniel Jordan 
Reviewed-by: Laurent Dufour 
Reviewed-by: Vlastimil Babka 
Cc: Davidlohr Bueso 
Cc: David Rientjes 
Cc: Hugh Dickins 
Cc: Jason Gunthorpe 
Cc: Jerome Glisse 
Cc: John Hubbard 
Cc: Liam Howlett 
Cc: Matthew Wilcox 
Cc: Peter Zijlstra 
Cc: Ying Han 
Link: http://lkml.kernel.org/r/20200520052908.204642-5-walken@google.com
Signed-off-by: Linus Torvalds

binder: Handle start==NULL in binder_update_page_range()

2019-11-14T03:44:47+00:00

The old loop wouldn't stop when reaching `start` if `start==NULL`, instead
continuing backwards to index -1 and crashing.

Luckily you need to be highly privileged to map things at NULL, so it's not
a big problem.

Fix it by adjusting the loop so that the loop variable is always in bounds.

This patch is deliberately minimal to simplify backporting, but IMO this
function could use a refactor. The jump labels in the second loop body are
horrible (the error gotos should be jumping to free_range instead), and
both loops would look nicer if they just iterated upwards through indices.
And the up_read()+mmput() shouldn't be duplicated like that.

Cc: stable@vger.kernel.org
Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Signed-off-by: Jann Horn 
Acked-by: Christian Brauner 
Link: https://lore.kernel.org/r/20191018205631.248274-3-jannh@google.com
Signed-off-by: Greg Kroah-Hartman

binder: Prevent repeated use of ->mmap() via NULL mapping

2019-11-14T03:44:47+00:00

binder_alloc_mmap_handler() attempts to detect the use of ->mmap() on a
binder_proc whose binder_alloc has already been initialized by checking
whether alloc->buffer is non-zero.

Before commit 880211667b20 ("binder: remove kernel vm_area for buffer
space"), alloc->buffer was a kernel mapping address, which is always
non-zero, but since that commit, it is a userspace mapping address.

A sufficiently privileged user can map /dev/binder at NULL, tricking
binder_alloc_mmap_handler() into assuming that the binder_proc has not been
mapped yet. This leads to memory unsafety.
Luckily, no context on Android has such privileges, and on a typical Linux
desktop system, you need to be root to do that.

Fix it by using the mapping size instead of the mapping address to
distinguish the mapped case. A valid VMA can't have size zero.

Fixes: 880211667b20 ("binder: remove kernel vm_area for buffer space")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn 
Acked-by: Christian Brauner 
Link: https://lore.kernel.org/r/20191018205631.248274-2-jannh@google.com
Signed-off-by: Greg Kroah-Hartman

binder: Fix race between mmap() and binder_alloc_print_pages()

2019-11-14T03:44:46+00:00

binder_alloc_print_pages() iterates over
alloc->pages[0..alloc->buffer_size-1] under alloc->mutex.
binder_alloc_mmap_handler() writes alloc->pages and alloc->buffer_size
without holding that lock, and even writes them before the last bailout
point.

Unfortunately we can't take the alloc->mutex in the ->mmap() handler
because mmap_sem can be taken while alloc->mutex is held.
So instead, we have to locklessly check whether the binder_alloc has been
fully initialized with binder_alloc_get_vma(), like in
binder_alloc_new_buf_locked().

Fixes: 8ef4665aa129 ("android: binder: Add page usage in binder stats")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn 
Acked-by: Christian Brauner 
Link: https://lore.kernel.org/r/20191018205631.248274-1-jannh@google.com
Signed-off-by: Greg Kroah-Hartman

Merge 5.4-rc5 into char-misc-next

2019-10-27T17:48:33+00:00

We want the binder fix in here as well for testing and to work on top
of.

Also handles a merge issue in binder.c to help linux-next out

Signed-off-by: Greg Kroah-Hartman

binder: Remove incorrect comment about vm_insert_page() behavior

2019-10-21T16:30:49+00:00

vm_insert_page() does increment the page refcount, and just to be sure,
I've confirmed it by printing page_count(page[0].page_ptr) before and after
vm_insert_page(). It's 1 before, 2 afterwards, as expected.

Fixes: a145dd411eb2 ("VM: add "vm_insert_page()" function")
Signed-off-by: Jann Horn 
Acked-by: Christian Brauner 
Link: https://lore.kernel.org/r/20191018153946.128584-1-jannh@google.com
Signed-off-by: Greg Kroah-Hartman

binder: Don't modify VMA bounds in ->mmap handler

2019-10-17T12:58:44+00:00

binder_mmap() tries to prevent the creation of overly big binder mappings
by silently truncating the size of the VMA to 4MiB. However, this violates
the API contract of mmap(). If userspace attempts to create a large binder
VMA, and later attempts to unmap that VMA, it will call munmap() on a range
beyond the end of the VMA, which may have been allocated to another VMA in
the meantime. This can lead to userspace memory corruption.

The following sequence of calls leads to a segfault without this commit:

int main(void) {
  int binder_fd = open("/dev/binder", O_RDWR);
  if (binder_fd == -1) err(1, "open binder");
  void *binder_mapping = mmap(NULL, 0x800000UL, PROT_READ, MAP_SHARED,
                              binder_fd, 0);
  if (binder_mapping == MAP_FAILED) err(1, "mmap binder");
  void *data_mapping = mmap(NULL, 0x400000UL, PROT_READ|PROT_WRITE,
                            MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
  if (data_mapping == MAP_FAILED) err(1, "mmap data");
  munmap(binder_mapping, 0x800000UL);
  *(char*)data_mapping = 1;
  return 0;
}

Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn 
Acked-by: Todd Kjos 
Acked-by: Christian Brauner 
Link: https://lore.kernel.org/r/20191016150119.154756-1-jannh@google.com
Signed-off-by: Greg Kroah-Hartman