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linux-next/io_uring
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Harshit Mogalapalli 998b30c394 io_uring: Fix a null-ptr-deref in io_tctx_exit_cb() 
Syzkaller reports a NULL deref bug as follows:

 BUG: KASAN: null-ptr-deref in io_tctx_exit_cb+0x53/0xd3
 Read of size 4 at addr 0000000000000138 by task file1/1955

 CPU: 1 PID: 1955 Comm: file1 Not tainted 6.1.0-rc7-00103-gef4d3ea40565 #75
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
 Call Trace:
  <TASK>
  dump_stack_lvl+0xcd/0x134
  ? io_tctx_exit_cb+0x53/0xd3
  kasan_report+0xbb/0x1f0
  ? io_tctx_exit_cb+0x53/0xd3
  kasan_check_range+0x140/0x190
  io_tctx_exit_cb+0x53/0xd3
  task_work_run+0x164/0x250
  ? task_work_cancel+0x30/0x30
  get_signal+0x1c3/0x2440
  ? lock_downgrade+0x6e0/0x6e0
  ? lock_downgrade+0x6e0/0x6e0
  ? exit_signals+0x8b0/0x8b0
  ? do_raw_read_unlock+0x3b/0x70
  ? do_raw_spin_unlock+0x50/0x230
  arch_do_signal_or_restart+0x82/0x2470
  ? kmem_cache_free+0x260/0x4b0
  ? putname+0xfe/0x140
  ? get_sigframe_size+0x10/0x10
  ? do_execveat_common.isra.0+0x226/0x710
  ? lockdep_hardirqs_on+0x79/0x100
  ? putname+0xfe/0x140
  ? do_execveat_common.isra.0+0x238/0x710
  exit_to_user_mode_prepare+0x15f/0x250
  syscall_exit_to_user_mode+0x19/0x50
  do_syscall_64+0x42/0xb0
  entry_SYSCALL_64_after_hwframe+0x63/0xcd
 RIP: 0023:0x0
 Code: Unable to access opcode bytes at 0xffffffffffffffd6.
 RSP: 002b:00000000fffb7790 EFLAGS: 00000200 ORIG_RAX: 000000000000000b
 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
  </TASK>
 Kernel panic - not syncing: panic_on_warn set ...

This happens because the adding of task_work from io_ring_exit_work()
isn't synchronized with canceling all work items from eg exec. The
execution of the two are ordered in that they are both run by the task
itself, but if io_tctx_exit_cb() is queued while we're canceling all
work items off exec AND gets executed when the task exits to userspace
rather than in the main loop in io_uring_cancel_generic(), then we can
find current->io_uring == NULL and hit the above crash.

It's safe to add this NULL check here, because the execution of the two
paths are done by the task itself.

Cc: stable@vger.kernel.org
Fixes: d56d938b4b ("io_uring: do ctx initiated file note removal")
Reported-by: syzkaller <syzkaller@googlegroups.com>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
Link: https://lore.kernel.org/r/20221206093833.3812138-1-harshit.m.mogalapalli@oracle.com
[axboe: add code comment and also put an explanation in the commit msg]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2022-12-07 06:45:20 -07:00
..
advise.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
advise.h
alloc_cache.h
cancel.c io_uring: add IORING_SETUP_DEFER_TASKRUN 2022-09-21 10:30:42 -06:00
cancel.h
epoll.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
epoll.h
fdinfo.c io_uring: fix fdinfo sqe offsets calculation 2022-10-12 16:30:56 -06:00
fdinfo.h
filetable.c io_uring/filetable: fix file reference underflow 2022-11-25 06:54:46 -07:00
filetable.h io_uring: kill hot path fixed file bitmap debug checks 2022-10-16 17:07:53 -06:00
fs.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
fs.h
io_uring.c io_uring: Fix a null-ptr-deref in io_tctx_exit_cb() 2022-12-07 06:45:20 -07:00
io_uring.h io_uring: clear TIF_NOTIFY_SIGNAL if set and task_work not available 2022-11-25 10:55:08 -07:00
io-wq.c io-wq: Fix memory leak in worker creation 2022-10-20 05:48:59 -07:00
io-wq.h
kbuf.c io_uring: check for rollover of buffer ID when providing buffers 2022-11-10 11:07:41 -07:00
kbuf.h io_uring: allow buffer recycling in READV 2022-09-21 10:30:43 -06:00
Makefile
msg_ring.c io_uring/msg_ring: Fix NULL pointer dereference in io_msg_send_fd() 2022-10-19 12:33:33 -07:00
msg_ring.h
net.c io_uring: fix multishot recv request leaks 2022-11-17 12:33:33 -07:00
net.h io_uring/net: zerocopy sendmsg 2022-09-21 13:15:02 -06:00
nop.c
nop.h
notif.c io_uring/notif: Remove the unused function io_notif_complete() 2022-09-05 11:42:39 -06:00
notif.h io_uring/net: simplify zerocopy send user API 2022-09-01 09:13:33 -06:00
opdef.c io_uring/opdef: remove 'audit_skip' from SENDMSG_ZC 2022-10-12 16:30:56 -06:00
opdef.h io_uring: add custom opcode hooks on fail 2022-09-21 13:15:02 -06:00
openclose.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
openclose.h
poll.c io_uring/poll: fix poll_refs race with cancelation 2022-11-25 07:17:33 -07:00
poll.h
refs.h
rsrc.c io_uring: remove FFS_SCM 2022-10-16 17:07:12 -06:00
rsrc.h io_uring: remove FFS_SCM 2022-10-16 17:07:12 -06:00
rw.c io_uring/rw: remove leftover debug statement 2022-10-16 17:24:10 -06:00
rw.h io_uring/rw: don't lose partial IO result on fail 2022-09-21 13:15:02 -06:00
slist.h
splice.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
splice.h
sqpoll.c
sqpoll.h
statx.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
statx.h
sync.c io_uring: make io_kiocb_to_cmd() typesafe 2022-08-12 17:01:00 -06:00
sync.h
tctx.c io_uring: remove io_register_submitter 2022-10-07 12:25:30 -06:00
tctx.h io_uring: simplify __io_uring_add_tctx_node 2022-10-07 12:25:30 -06:00
timeout.c io_uring: remove unused return from io_disarm_next 2022-09-21 13:15:01 -06:00
timeout.h io_uring: remove unused return from io_disarm_next 2022-09-21 13:15:01 -06:00
uring_cmd.c io_uring: introduce fixed buffer support for io_uring_cmd 2022-09-30 07:50:59 -06:00
uring_cmd.h
xattr.c __io_setxattr(): constify path 2022-09-01 17:39:05 -04:00
xattr.h