Re: [PATCH rdma-next] RDMA/core: Fix double destruction of uobject

[Jason Gunthorpe <jgg@ziepe.ca>]

On Wed, May 27, 2020 at 04:55:34PM +0300, Leon Romanovsky wrote:
> From: Jason Gunthorpe <jgg@mellanox.com>
> 
> Fix use after free when user user space request uobject concurrently for
> the same object, within the RCU grace period.
> 
> In that case, remove_handle_idr_uobject() is called twice and we will have
> an extra put on the uobject which cause use after free.  Fix it by leaving
> the uobject write locked after it was removed from the idr.
> 
> Call to rdma_lookup_put_uobject with UVERBS_LOOKUP_DESTROY instead of
> UVERBS_LOOKUP_WRITE will do the work.
> 
> ------------[ cut here ]------------
> refcount_t: underflow; use-after-free.
> WARNING: CPU: 0 PID: 1381 at lib/refcount.c:28 refcount_warn_saturate+0xfe/0x1a0
> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 0 PID: 1381 Comm: syz-executor.0 Not tainted 5.5.0-rc3 #8
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014
> Call Trace:
>  dump_stack+0x94/0xce
>  panic+0x234/0x56f
>  __warn+0x1cc/0x1e1
>  report_bug+0x200/0x310
>  fixup_bug.part.11+0x32/0x80
>  do_error_trap+0xd3/0x100
>  do_invalid_op+0x31/0x40
>  invalid_op+0x1e/0x30
> RIP: 0010:refcount_warn_saturate+0xfe/0x1a0
> Code: 0f 0b eb 9b e8 23 f6 6d ff 80 3d 6c d4 19 03 00 75 8d e8 15 f6 6d ff 48 c7 c7 c0 02 55 bd c6 05 57 d4 19 03 01 e8 a2 58 49 ff <0f> 0b e9 6e ff ff ff e8 f6 f5 6d ff 80 3d 42 d4 19 03 00 0f 85 5c
> RSP: 0018:ffffc90002df7b98 EFLAGS: 00010282
> RAX: 0000000000000000 RBX: ffff88810f6a193c RCX: ffffffffba649009
> RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88811b0283cc
> RBP: 0000000000000003 R08: ffffed10236060e3 R09: ffffed10236060e3
> R10: 0000000000000001 R11: ffffed10236060e2 R12: ffff88810f6a193c
> R13: ffffc90002df7d60 R14: 0000000000000000 R15: ffff888116ae6a08
>  uverbs_uobject_put+0xfd/0x140
>  __uobj_perform_destroy+0x3d/0x60
>  ib_uverbs_close_xrcd+0x148/0x170
>  ib_uverbs_write+0xaa5/0xdf0
>  __vfs_write+0x7c/0x100
>  vfs_write+0x168/0x4a0
>  ksys_write+0xc8/0x200
>  do_syscall_64+0x9c/0x390
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x465b49
> Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f759d122c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 000000000073bfa8 RCX: 0000000000465b49
> RDX: 000000000000000c RSI: 0000000020000080 RDI: 0000000000000003
> RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f759d1236bc
> R13: 00000000004ca27c R14: 000000000070de40 R15: 00000000ffffffff
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: 0x39400000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
> 
> Fixes: 7452a3c745a2 ("IB/uverbs: Allow RDMA_REMOVE_DESTROY to work concurrently with disassociate")
> Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
> Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
> Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
> ---
>  drivers/infiniband/core/rdma_core.c | 20 +++++++++++++-------
>  include/rdma/uverbs_std_types.h     |  2 +-
>  2 files changed, 14 insertions(+), 8 deletions(-)

Applied to for-rc, thanks

Jason