Patch "RDMA/uverbs: Fix bad unlock balance in ib_uverbs_close_xrcd" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

RDMA/uverbs: Fix bad unlock balance in ib_uverbs_close_xrcd

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
rdma-uverbs-fix-bad-unlock-balance-in-ib_uverbs_close_xrcd.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Leon Romanovsky <[email protected]>
Date: Wed, 14 Feb 2018 12:35:38 +0200
Subject: RDMA/uverbs: Fix bad unlock balance in ib_uverbs_close_xrcd

From: Leon Romanovsky <[email protected]>

commit 5c2e1c4f926856717f3fd31932e926dc3fe77ebd upstream.

There is no matching lock for this mutex. Git history suggests this is just a missed remnant from an earlier version of the function before this locking was moved into uverbs_free_xrcd.

Originally this lock was protecting the xrcd_table_delete()

=====================================
WARNING: bad unlock balance detected!
4.15.0+ #87 Not tainted
-------------------------------------
syzkaller223405/269 is trying to release lock (&uverbs_dev->xrcd_tree_mutex) at:
[<00000000b8703372>] ib_uverbs_close_xrcd+0x195/0x1f0
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syzkaller223405/269:
#0: (&uverbs_dev->disassociate_srcu){....}, at: [<000000005af3b960>] ib_uverbs_write+0x265/0xef0

stack backtrace:
CPU: 0 PID: 269 Comm: syzkaller223405 Not tainted 4.15.0+ #87
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
Call Trace:
 dump_stack+0xde/0x164
 ? dma_virt_map_sg+0x22c/0x22c
 ? ib_uverbs_write+0x265/0xef0
 ? console_unlock+0x502/0xbd0
 ? ib_uverbs_close_xrcd+0x195/0x1f0
 print_unlock_imbalance_bug+0x131/0x160
 lock_release+0x59d/0x1100
 ? ib_uverbs_close_xrcd+0x195/0x1f0
 ? lock_acquire+0x440/0x440
 ? lock_acquire+0x440/0x440
 __mutex_unlock_slowpath+0x88/0x670
 ? wait_for_completion+0x4c0/0x4c0
 ? rdma_lookup_get_uobject+0x145/0x2f0
 ib_uverbs_close_xrcd+0x195/0x1f0
 ? ib_uverbs_open_xrcd+0xdd0/0xdd0
 ib_uverbs_write+0x7f9/0xef0
 ? cyc2ns_read_end+0x10/0x10
 ? ib_uverbs_open_xrcd+0xdd0/0xdd0
 ? uverbs_devnode+0x110/0x110
 ? cyc2ns_read_end+0x10/0x10
 ? cyc2ns_read_end+0x10/0x10
 ? sched_clock_cpu+0x18/0x200
 __vfs_write+0x10d/0x700
 ? uverbs_devnode+0x110/0x110
 ? kernel_read+0x170/0x170
 ? __fget+0x358/0x5d0
 ? security_file_permission+0x93/0x260
 vfs_write+0x1b0/0x550
 SyS_write+0xc7/0x1a0
 ? SyS_read+0x1a0/0x1a0
 ? trace_hardirqs_on_thunk+0x1a/0x1c
 entry_SYSCALL_64_fastpath+0x1e/0x8b
RIP: 0033:0x4335c9

---
 drivers/infiniband/core/uverbs_cmd.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

@@ -601,10 +601,8 @@ ssize_t ib_uverbs_close_xrcd(struct ib_u
 
 	uobj  = uobj_get_write(uobj_get_type(xrcd), cmd.xrcd_handle,
 			       file->ucontext);
-	if (IS_ERR(uobj)) {
-		mutex_unlock(&file->device->xrcd_tree_mutex);
+	if (IS_ERR(uobj))
 		return PTR_ERR(uobj);
-	}
 
 	ret = uobj_remove_commit(uobj);
 	return ret ?: in_len;

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/rdma-uverbs-fix-bad-unlock-balance-in-ib_uverbs_close_xrcd.patch queue-4.15/rdma-uverbs-fix-circular-locking-dependency.patch queue-4.15/rdma-uverbs-sanitize-user-entered-port-numbers-prior-to-access-it.patch queue-4.15/rdma-uverbs-protect-from-races-between-lookup-and-destroy-of-uobjects.patch queue-4.15/rdma-uverbs-protect-from-command-mask-overflow.patch