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Subject[PATCH 4.15 20/64] RDMA/uverbs: Fix circular locking dependency
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Leon Romanovsky <leonro@mellanox.com>

commit 1ff5325c3ca1843228a86549318bbd3b414b9207 upstream.

Avoid circular locking dependency by calling
to uobj_alloc_commit() outside of xrcd_tree_mutex lock.

======================================================
WARNING: possible circular locking dependency detected
4.15.0+ #87 Not tainted
------------------------------------------------------
syzkaller401056/269 is trying to acquire lock:
(&uverbs_dev->xrcd_tree_mutex){+.+.}, at: [<000000006c12d2cd>] uverbs_free_xrcd+0xd2/0x360

but task is already holding lock:
(&ucontext->uobjects_lock){+.+.}, at: [<00000000da010f09>] uverbs_cleanup_ucontext+0x168/0x730

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #1 (&ucontext->uobjects_lock){+.+.}:
__mutex_lock+0x111/0x1720
rdma_alloc_commit_uobject+0x22c/0x600
ib_uverbs_open_xrcd+0x61a/0xdd0
ib_uverbs_write+0x7f9/0xef0
__vfs_write+0x10d/0x700
vfs_write+0x1b0/0x550
SyS_write+0xc7/0x1a0
entry_SYSCALL_64_fastpath+0x1e/0x8b

-> #0 (&uverbs_dev->xrcd_tree_mutex){+.+.}:
lock_acquire+0x19d/0x440
__mutex_lock+0x111/0x1720
uverbs_free_xrcd+0xd2/0x360
remove_commit_idr_uobject+0x6d/0x110
uverbs_cleanup_ucontext+0x2f0/0x730
ib_uverbs_cleanup_ucontext.constprop.3+0x52/0x120
ib_uverbs_close+0xf2/0x570
__fput+0x2cd/0x8d0
task_work_run+0xec/0x1d0
do_exit+0x6a1/0x1520
do_group_exit+0xe8/0x380
SyS_exit_group+0x1e/0x20
entry_SYSCALL_64_fastpath+0x1e/0x8b

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&ucontext->uobjects_lock);
lock(&uverbs_dev->xrcd_tree_mutex);
lock(&ucontext->uobjects_lock);
lock(&uverbs_dev->xrcd_tree_mutex);

*** DEADLOCK ***

3 locks held by syzkaller401056/269:
#0: (&file->cleanup_mutex){+.+.}, at: [<00000000c9f0c252>] ib_uverbs_close+0xac/0x570
#1: (&ucontext->cleanup_rwsem){++++}, at: [<00000000b6994d49>] uverbs_cleanup_ucontext+0xf6/0x730
#2: (&ucontext->uobjects_lock){+.+.}, at: [<00000000da010f09>] uverbs_cleanup_ucontext+0x168/0x730

stack backtrace:
CPU: 0 PID: 269 Comm: syzkaller401056 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
? uverbs_cleanup_ucontext+0x168/0x730
? console_unlock+0x502/0xbd0
print_circular_bug.isra.24+0x35e/0x396
? print_circular_bug_header+0x12e/0x12e
? find_usage_backwards+0x30/0x30
? entry_SYSCALL_64_fastpath+0x1e/0x8b
validate_chain.isra.28+0x25d1/0x40c0
? check_usage+0xb70/0xb70
? graph_lock+0x160/0x160
? find_usage_backwards+0x30/0x30
? cyc2ns_read_end+0x10/0x10
? print_irqtrace_events+0x280/0x280
? __lock_acquire+0x93d/0x1630
__lock_acquire+0x93d/0x1630
lock_acquire+0x19d/0x440
? uverbs_free_xrcd+0xd2/0x360
__mutex_lock+0x111/0x1720
? uverbs_free_xrcd+0xd2/0x360
? uverbs_free_xrcd+0xd2/0x360
? __mutex_lock+0x828/0x1720
? mutex_lock_io_nested+0x1550/0x1550
? uverbs_cleanup_ucontext+0x168/0x730
? __lock_acquire+0x9a9/0x1630
? mutex_lock_io_nested+0x1550/0x1550
? uverbs_cleanup_ucontext+0xf6/0x730
? lock_contended+0x11a0/0x11a0
? uverbs_free_xrcd+0xd2/0x360
uverbs_free_xrcd+0xd2/0x360
remove_commit_idr_uobject+0x6d/0x110
uverbs_cleanup_ucontext+0x2f0/0x730
? sched_clock_cpu+0x18/0x200
? uverbs_close_fd+0x1c0/0x1c0
ib_uverbs_cleanup_ucontext.constprop.3+0x52/0x120
ib_uverbs_close+0xf2/0x570
? ib_uverbs_remove_one+0xb50/0xb50
? ib_uverbs_remove_one+0xb50/0xb50
__fput+0x2cd/0x8d0
task_work_run+0xec/0x1d0
do_exit+0x6a1/0x1520
? fsnotify_first_mark+0x220/0x220
? exit_notify+0x9f0/0x9f0
? entry_SYSCALL_64_fastpath+0x5/0x8b
? entry_SYSCALL_64_fastpath+0x5/0x8b
? trace_hardirqs_on_thunk+0x1a/0x1c
? time_hardirqs_on+0x27/0x670
? time_hardirqs_off+0x27/0x490
? syscall_return_slowpath+0x6c/0x460
? entry_SYSCALL_64_fastpath+0x5/0x8b
do_group_exit+0xe8/0x380
SyS_exit_group+0x1e/0x20
entry_SYSCALL_64_fastpath+0x1e/0x8b
RIP: 0033:0x431ce9

Cc: syzkaller <syzkaller@googlegroups.com>
Cc: <stable@vger.kernel.org> # 4.11
Fixes: fd3c7904db6e ("IB/core: Change idr objects to use the new schema")
Reported-by: Noa Osherovich <noaos@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/infiniband/core/uverbs_cmd.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -560,9 +560,10 @@ ssize_t ib_uverbs_open_xrcd(struct ib_uv
if (f.file)
fdput(f);

+ mutex_unlock(&file->device->xrcd_tree_mutex);
+
uobj_alloc_commit(&obj->uobject);

- mutex_unlock(&file->device->xrcd_tree_mutex);
return in_len;

err_copy:

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