This is a note to let you know that I've just added the patch titled
usb: gadget: f_fs: Fix possibe deadlock
to the 4.4-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:
usb-gadget-f_fs-fix-possibe-deadlock.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b3ce3ce02d146841af012d08506b4071db8ffde3 Mon Sep 17 00:00:00 2001
From: Baolin Wang <baolin.wang@xxxxxxxxxx>
Date: Thu, 8 Dec 2016 19:55:22 +0800
Subject: usb: gadget: f_fs: Fix possibe deadlock
From: Baolin Wang <baolin.wang@xxxxxxxxxx>
commit b3ce3ce02d146841af012d08506b4071db8ffde3 upstream.
When system try to close /dev/usb-ffs/adb/ep0 on one core, at the same
time another core try to attach new UDC, which will cause deadlock as
below scenario. Thus we should release ffs lock before issuing
unregister_gadget_item().
[ 52.642225] c1 ======================================================
[ 52.642228] c1 [ INFO: possible circular locking dependency detected ]
[ 52.642236] c1 4.4.6+ #1 Tainted: G W O
[ 52.642241] c1 -------------------------------------------------------
[ 52.642245] c1 usb ffs open/2808 is trying to acquire lock:
[ 52.642270] c0 (udc_lock){+.+.+.}, at: [<ffffffc00065aeec>]
usb_gadget_unregister_driver+0x3c/0xc8
[ 52.642272] c1 but task is already holding lock:
[ 52.642283] c0 (ffs_lock){+.+.+.}, at: [<ffffffc00066b244>]
ffs_data_clear+0x30/0x140
[ 52.642285] c1 which lock already depends on the new lock.
[ 52.642287] c1
the existing dependency chain (in reverse order) is:
[ 52.642295] c0
-> #1 (ffs_lock){+.+.+.}:
[ 52.642307] c0 [<ffffffc00012340c>] __lock_acquire+0x20f0/0x2238
[ 52.642314] c0 [<ffffffc000123b54>] lock_acquire+0xe4/0x298
[ 52.642322] c0 [<ffffffc000aaf6e8>] mutex_lock_nested+0x7c/0x3cc
[ 52.642328] c0 [<ffffffc00066f7bc>] ffs_func_bind+0x504/0x6e8
[ 52.642334] c0 [<ffffffc000654004>] usb_add_function+0x84/0x184
[ 52.642340] c0 [<ffffffc000658ca4>] configfs_composite_bind+0x264/0x39c
[ 52.642346] c0 [<ffffffc00065b348>] udc_bind_to_driver+0x58/0x11c
[ 52.642352] c0 [<ffffffc00065b49c>] usb_udc_attach_driver+0x90/0xc8
[ 52.642358] c0 [<ffffffc0006598e0>] gadget_dev_desc_UDC_store+0xd4/0x128
[ 52.642369] c0 [<ffffffc0002c14e8>] configfs_write_file+0xd0/0x13c
[ 52.642376] c0 [<ffffffc00023c054>] vfs_write+0xb8/0x214
[ 52.642381] c0 [<ffffffc00023cad4>] SyS_write+0x54/0xb0
[ 52.642388] c0 [<ffffffc000085ff0>] el0_svc_naked+0x24/0x28
[ 52.642395] c0
-> #0 (udc_lock){+.+.+.}:
[ 52.642401] c0 [<ffffffc00011e3d0>] print_circular_bug+0x84/0x2e4
[ 52.642407] c0 [<ffffffc000123454>] __lock_acquire+0x2138/0x2238
[ 52.642412] c0 [<ffffffc000123b54>] lock_acquire+0xe4/0x298
[ 52.642420] c0 [<ffffffc000aaf6e8>] mutex_lock_nested+0x7c/0x3cc
[ 52.642427] c0 [<ffffffc00065aeec>] usb_gadget_unregister_driver+0x3c/0xc8
[ 52.642432] c0 [<ffffffc00065995c>] unregister_gadget_item+0x28/0x44
[ 52.642439] c0 [<ffffffc00066b34c>] ffs_data_clear+0x138/0x140
[ 52.642444] c0 [<ffffffc00066b374>] ffs_data_reset+0x20/0x6c
[ 52.642450] c0 [<ffffffc00066efd0>] ffs_data_closed+0xac/0x12c
[ 52.642454] c0 [<ffffffc00066f070>] ffs_ep0_release+0x20/0x2c
[ 52.642460] c0 [<ffffffc00023dbe4>] __fput+0xb0/0x1f4
[ 52.642466] c0 [<ffffffc00023dd9c>] ____fput+0x20/0x2c
[ 52.642473] c0 [<ffffffc0000ee944>] task_work_run+0xb4/0xe8
[ 52.642482] c0 [<ffffffc0000cd45c>] do_exit+0x360/0xb9c
[ 52.642487] c0 [<ffffffc0000cf228>] do_group_exit+0x4c/0xb0
[ 52.642494] c0 [<ffffffc0000dd3c8>] get_signal+0x380/0x89c
[ 52.642501] c0 [<ffffffc00008a8f0>] do_signal+0x154/0x518
[ 52.642507] c0 [<ffffffc00008af00>] do_notify_resume+0x70/0x78
[ 52.642512] c0 [<ffffffc000085ee8>] work_pending+0x1c/0x20
[ 52.642514] c1
other info that might help us debug this:
[ 52.642517] c1 Possible unsafe locking scenario:
[ 52.642518] c1 CPU0 CPU1
[ 52.642520] c1 ---- ----
[ 52.642525] c0 lock(ffs_lock);
[ 52.642529] c0 lock(udc_lock);
[ 52.642533] c0 lock(ffs_lock);
[ 52.642537] c0 lock(udc_lock);
[ 52.642539] c1
*** DEADLOCK ***
[ 52.642543] c1 1 lock held by usb ffs open/2808:
[ 52.642555] c0 #0: (ffs_lock){+.+.+.}, at: [<ffffffc00066b244>]
ffs_data_clear+0x30/0x140
[ 52.642557] c1 stack backtrace:
[ 52.642563] c1 CPU: 1 PID: 2808 Comm: usb ffs open Tainted: G
[ 52.642565] c1 Hardware name: Spreadtrum SP9860g Board (DT)
[ 52.642568] c1 Call trace:
[ 52.642573] c1 [<ffffffc00008b430>] dump_backtrace+0x0/0x170
[ 52.642577] c1 [<ffffffc00008b5c0>] show_stack+0x20/0x28
[ 52.642583] c1 [<ffffffc000422694>] dump_stack+0xa8/0xe0
[ 52.642587] c1 [<ffffffc00011e548>] print_circular_bug+0x1fc/0x2e4
[ 52.642591] c1 [<ffffffc000123454>] __lock_acquire+0x2138/0x2238
[ 52.642595] c1 [<ffffffc000123b54>] lock_acquire+0xe4/0x298
[ 52.642599] c1 [<ffffffc000aaf6e8>] mutex_lock_nested+0x7c/0x3cc
[ 52.642604] c1 [<ffffffc00065aeec>] usb_gadget_unregister_driver+0x3c/0xc8
[ 52.642608] c1 [<ffffffc00065995c>] unregister_gadget_item+0x28/0x44
[ 52.642613] c1 [<ffffffc00066b34c>] ffs_data_clear+0x138/0x140
[ 52.642618] c1 [<ffffffc00066b374>] ffs_data_reset+0x20/0x6c
[ 52.642621] c1 [<ffffffc00066efd0>] ffs_data_closed+0xac/0x12c
[ 52.642625] c1 [<ffffffc00066f070>] ffs_ep0_release+0x20/0x2c
[ 52.642629] c1 [<ffffffc00023dbe4>] __fput+0xb0/0x1f4
[ 52.642633] c1 [<ffffffc00023dd9c>] ____fput+0x20/0x2c
[ 52.642636] c1 [<ffffffc0000ee944>] task_work_run+0xb4/0xe8
[ 52.642640] c1 [<ffffffc0000cd45c>] do_exit+0x360/0xb9c
[ 52.642644] c1 [<ffffffc0000cf228>] do_group_exit+0x4c/0xb0
[ 52.642647] c1 [<ffffffc0000dd3c8>] get_signal+0x380/0x89c
[ 52.642651] c1 [<ffffffc00008a8f0>] do_signal+0x154/0x518
[ 52.642656] c1 [<ffffffc00008af00>] do_notify_resume+0x70/0x78
[ 52.642659] c1 [<ffffffc000085ee8>] work_pending+0x1c/0x20
Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx>
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxx>
Signed-off-by: Felipe Balbi <felipe.balbi@xxxxxxxxxxxxxxx>
Cc: Jerry Zhang <zhangjerry@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/gadget/function/f_fs.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -3463,6 +3463,7 @@ static void ffs_closed(struct ffs_data *
{
struct ffs_dev *ffs_obj;
struct f_fs_opts *opts;
+ struct config_item *ci;
ENTER();
ffs_dev_lock();
@@ -3486,8 +3487,11 @@ static void ffs_closed(struct ffs_data *
|| !atomic_read(&opts->func_inst.group.cg_item.ci_kref.refcount))
goto done;
- unregister_gadget_item(ffs_obj->opts->
- func_inst.group.cg_item.ci_parent->ci_parent);
+ ci = opts->func_inst.group.cg_item.ci_parent->ci_parent;
+ ffs_dev_unlock();
+
+ unregister_gadget_item(ci);
+ return;
done:
ffs_dev_unlock();
}
Patches currently in stable-queue which might be from baolin.wang@xxxxxxxxxx are
queue-4.4/usb-gadget-f_fs-fix-possibe-deadlock.patch