linux-toradex.git/kernel/watch_queue.c, branch v5.19-rc8

watch-queue: remove spurious double semicolon

2022-07-21T17:30:14+00:00

Sedat Dilek noticed that I had an extraneous semicolon at the end of a
line in the previous patch.

It's harmless, but unintentional, and while compilers just treat it as
an extra empty statement, for all I know some other tooling might warn
about it. So clean it up before other people notice too ;)

Fixes: 353f7988dd84 ("watchqueue: make sure to serialize 'wqueue->defunct' properly")
Reported-by: Sedat Dilek 
Signed-off-by: Linus Torvalds 

Reported-by: Sedat Dilek

watchqueue: make sure to serialize 'wqueue->defunct' properly

2022-07-20T17:46:07+00:00

When the pipe is closed, we mark the associated watchqueue defunct by
calling watch_queue_clear().  However, while that is protected by the
watchqueue lock, new watchqueue entries aren't actually added under that
lock at all: they use the pipe->rd_wait.lock instead, and looking up
that pipe happens without any locking.

The watchqueue code uses the RCU read-side section to make sure that the
wqueue entry itself hasn't disappeared, but that does not protect the
pipe_info in any way.

So make sure to actually hold the wqueue lock when posting watch events,
properly serializing against the pipe being torn down.

Reported-by: Noam Rathaus 
Cc: Greg KH 
Cc: David Howells 
Signed-off-by: Linus Torvalds

watch_queue: Free the page array when watch_queue is dismantled

2022-04-02T17:37:39+00:00

Commit 7ea1a0124b6d ("watch_queue: Free the alloc bitmap when the
watch_queue is torn down") took care of the bitmap, but not the page
array.

  BUG: memory leak
  unreferenced object 0xffff88810d9bc140 (size 32):
  comm "syz-executor335", pid 3603, jiffies 4294946994 (age 12.840s)
  hex dump (first 32 bytes):
    40 a7 40 04 00 ea ff ff 00 00 00 00 00 00 00 00  @.@.............
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
     kmalloc_array include/linux/slab.h:621 [inline]
     kcalloc include/linux/slab.h:652 [inline]
     watch_queue_set_size+0x12f/0x2e0 kernel/watch_queue.c:251
     pipe_ioctl+0x82/0x140 fs/pipe.c:632
     vfs_ioctl fs/ioctl.c:51 [inline]
     __do_sys_ioctl fs/ioctl.c:874 [inline]
     __se_sys_ioctl fs/ioctl.c:860 [inline]
     __x64_sys_ioctl+0xfc/0x140 fs/ioctl.c:860
     do_syscall_x64 arch/x86/entry/common.c:50 [inline]

Reported-by: syzbot+25ea042ae28f3888727a@syzkaller.appspotmail.com
Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Signed-off-by: Eric Dumazet 
Signed-off-by: David Howells 
Cc: Jann Horn 
Link: https://lore.kernel.org/r/20220322004654.618274-1-eric.dumazet@gmail.com/
Signed-off-by: Linus Torvalds

watch_queue: Actually free the watch

2022-03-21T12:48:32+00:00

free_watch() does everything barring actually freeing the watch object.  Fix
this by adding the missing kfree.

kmemleak produces a report something like the following.  Note that as an
address can be seen in the first word, the watch would appear to have gone
through call_rcu().

BUG: memory leak
unreferenced object 0xffff88810ce4a200 (size 96):
  comm "syz-executor352", pid 3605, jiffies 4294947473 (age 13.720s)
  hex dump (first 32 bytes):
    e0 82 48 0d 81 88 ff ff 00 00 00 00 00 00 00 00  ..H.............
    80 a2 e4 0c 81 88 ff ff 00 00 00 00 00 00 00 00  ................
  backtrace:
    [] kmalloc include/linux/slab.h:581 [inline]
    [] kzalloc include/linux/slab.h:714 [inline]
    [] keyctl_watch_key+0xec/0x2e0 security/keys/keyctl.c:1800
    [] __do_sys_keyctl+0x3c4/0x490 security/keys/keyctl.c:2016
    [] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    [] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
    [] entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-and-tested-by: syzbot+6e2de48f06cdb2884bfc@syzkaller.appspotmail.com
Signed-off-by: David Howells

watch_queue: Fix NULL dereference in error cleanup

2022-03-21T12:43:47+00:00

In watch_queue_set_size(), the error cleanup code doesn't take account of
the fact that __free_page() can't handle a NULL pointer when trying to free
up buffer pages that did get allocated.

Fix this by only calling __free_page() on the pages actually allocated.

Without the fix, this can lead to something like the following:

BUG: KASAN: null-ptr-deref in __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
Read of size 4 at addr 0000000000000034 by task syz-executor168/3599
...
Call Trace:
 
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 __kasan_report mm/kasan/report.c:446 [inline]
 kasan_report.cold+0x66/0xdf mm/kasan/report.c:459
 check_region_inline mm/kasan/generic.c:183 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:71 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
 page_ref_count include/linux/page_ref.h:67 [inline]
 put_page_testzero include/linux/mm.h:717 [inline]
 __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473
 watch_queue_set_size+0x499/0x630 kernel/watch_queue.c:275
 pipe_ioctl+0xac/0x2b0 fs/pipe.c:632
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl fs/ioctl.c:860 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-and-tested-by: syzbot+d55757faa9b80590767b@syzkaller.appspotmail.com
Signed-off-by: David Howells 
Reviewed-by: Fabio M. De Francesco

watch_queue: Make comment about setting ->defunct more accurate

2022-03-11T18:17:13+00:00

watch_queue_clear() has a comment stating that setting ->defunct to true
preventing new additions as well as preventing notifications.  Whilst
the latter is true, the first bit is superfluous since at the time this
function is called, the pipe cannot be accessed to add new event
sources.

Remove the "new additions" bit from the comment.

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-by: Jann Horn 
Signed-off-by: David Howells 
Signed-off-by: Linus Torvalds

watch_queue: Fix lack of barrier/sync/lock between post and read

2022-03-11T18:17:13+00:00

There's nothing to synchronise post_one_notification() versus
pipe_read().  Whilst posting is done under pipe->rd_wait.lock, the
reader only takes pipe->mutex which cannot bar notification posting as
that may need to be made from contexts that cannot sleep.

Fix this by setting pipe->head with a barrier in post_one_notification()
and reading pipe->head with a barrier in pipe_read().

If that's not sufficient, the rd_wait.lock will need to be taken,
possibly in a ->confirm() op so that it only applies to notifications.
The lock would, however, have to be dropped before copy_page_to_iter()
is invoked.

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-by: Jann Horn 
Signed-off-by: David Howells 
Signed-off-by: Linus Torvalds

watch_queue: Free the alloc bitmap when the watch_queue is torn down

2022-03-11T18:17:13+00:00

Free the watch_queue note allocation bitmap when the watch_queue is
destroyed.

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-by: Jann Horn 
Signed-off-by: David Howells 
Signed-off-by: Linus Torvalds

watch_queue: Fix the alloc bitmap size to reflect notes allocated

2022-03-11T18:17:12+00:00

Currently, watch_queue_set_size() sets the number of notes available in
wqueue->nr_notes according to the number of notes allocated, but sets
the size of the bitmap to the unrounded number of notes originally asked
for.

Fix this by setting the bitmap size to the number of notes we're
actually going to make available (ie. the number allocated).

Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reported-by: Jann Horn 
Signed-off-by: David Howells 
Signed-off-by: Linus Torvalds

watch_queue: Use the bitmap API when applicable

2022-03-11T18:17:12+00:00

Use bitmap_alloc() to simplify code, improve the semantic and reduce
some open-coded arithmetic in allocator arguments.

Also change a memset(0xff) into an equivalent bitmap_fill() to keep
consistency.

Signed-off-by: Christophe JAILLET 
Signed-off-by: David Howells 
Signed-off-by: Linus Torvalds