The patch titled Subject: drivers/watchdog/: fix oops in reboot notifier handling in watchdog core code has been removed from the -mm tree. Its filename was watchdog-fix-uaf-in-reboot-notifier-handling-in-watchdog-core-code.patch

This patch was dropped because it was merged into mainline or a subsystem tree

------------------------------------------------------ From: Vladis Dronov vdronov@redhat.com Subject: drivers/watchdog/: fix oops in reboot notifier handling in watchdog core code

After commit 44ea39420fc9 ("drivers/watchdog: make use of devm_register_reboot_notifier()") the struct notifier_block reboot_nb in the struct watchdog_device is removed from the reboot notifiers chain at the time watchdog's chardev is closed. But at least in i6300esb.c case reboot_nb is embedded in the struct esb_dev which can be freed on its device removal and before the chardev is closed, thus an oops at reboot:

[ 7.728581] esb_probe: esb_dev.watchdog_device ffff91316f91ab28 ts# uname -r note the address ^^^ 5.5.0-rc5-ae6088-wdog ts# ./openwdog0 & [1] 696 ts# opened /dev/watchdog0, sleeping 10s... ts# echo 1 > /sys/devices/pci0000:00/0000:00:09.0/remove [ 178.086079] devres:rel_nodes: dev ffff91317668a0b0 data ffff91316f91ab= 28 esb_dev.watchdog_device.reboot_nb memory is freed here ^^^ ts# ...woken up [ 181.459010] devres:rel_nodes: dev ffff913171781000 data ffff913174a1da= e8 [ 181.460195] devm_unreg_reboot_notifier: res ffff913174a1dae8 nb ffff91= 316f91ab78 attempt to use memory already freed = ^^^ [ 181.461063] devm_unreg_reboot_notifier: nb->call 6b6b6b6b6b6b6b6b [ 181.461243] devm_unreg_reboot_notifier: nb->next 6b6b6b6b6b6b6b6b freed memory is filled with a slub poison ^^^ [1]+ Done ./openwdog0 ts# reboot [ 229.921862] systemd-shutdown[1]: Rebooting. [ 229.939265] notifier_call_chain: nb ffffffff9c6c2f20 nb->next ffffffff= 9c6d50c0 [ 229.943080] notifier_call_chain: nb ffffffff9c6d50c0 nb->next 6b6b6b6b= 6b6b6b6b [ 229.946054] notifier_call_chain: nb 6b6b6b6b6b6b6b6b INVAL [ 229.957584] general protection fault: 0000 [#1] SMP [ 229.958770] CPU: 0 PID: 1 Comm: systemd-shutdow Not tainted 5.5.0-rc5-= ae6088-wdog [ 229.960224] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), ... [ 229.963288] RIP: 0010:notifier_call_chain+0x66/0xd0 [ 229.969082] RSP: 0018:ffffb20dc0013d88 EFLAGS: 00010246 [ 229.970812] RAX: 000000000000002e RBX: 6b6b6b6b6b6b6b6b RCX: 000000000= 00008b3 [ 229.972929] RDX: 0000000000000000 RSI: 0000000000000096 RDI: ffffffff9= ccc46ac [ 229.975028] RBP: 0000000000000001 R08: 0000000000000000 R09: 000000000= 00008b3 [ 229.977039] R10: 0000000000000001 R11: ffffffff9c26c740 R12: 000000000= 0000000 [ 229.979155] R13: 6b6b6b6b6b6b6b6b R14: 0000000000000000 R15: 00000000f= ffffffa ... slub_debug=3DFZP poison ^^^ [ 229.989089] Call Trace: [ 229.990157] blocking_notifier_call_chain+0x43/0x59 [ 229.991401] kernel_restart_prepare+0x14/0x30 [ 229.992607] kernel_restart+0x9/0x30 [ 229.993800] __do_sys_reboot+0x1d2/0x210 [ 230.000149] do_syscall_64+0x3d/0x130 [ 230.001277] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 230.002639] RIP: 0033:0x7f5461bdd177 [ 230.016402] Modules linked in: i6300esb [ 230.050261] Kernel panic - not syncing: Attempted to kill init! exitco= de=3D0x0000000b

Fix the crash by reverting 44ea39420fc9 so unregister_reboot_notifier() is called when watchdog device is removed. This also makes handling of the reboot notifier unified with the handling of the restart handler, which is freed with unregister_restart_handler() in the same place.

Link: http://lkml.kernel.org/r/20200108125347.6067-1-vdronov@redhat.com Fixes: 44ea39420fc9 ("drivers/watchdog: make use of devm_register_reboot_= notifier()") Signed-off-by: Vladis Dronov vdronov@redhat.com Reviewed-by: Guenter Roeck linux@roeck-us.net Cc: Andrey Smirnov andrew.smirnov@gmail.com Cc: Wim Van Sebroeck wim@linux-watchdog.org Cc: Chris Healy cphealy@gmail.com Cc: Andy Shevchenko andy.shevchenko@gmail.com Cc: stable@vger.kernel.org [4.15+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

drivers/watchdog/watchdog_core.c | 35 ++++++++++++++++++++++++++++ drivers/watchdog/watchdog_dev.c | 36 ----------------------------- 2 files changed, 36 insertions(+), 35 deletions(-)

--- a/drivers/watchdog/watchdog_core.c~watchdog-fix-uaf-in-reboot-notifier-handling-in-watchdog-core-code +++ a/drivers/watchdog/watchdog_core.c @@ -147,6 +147,25 @@ int watchdog_init_timeout(struct watchdo } EXPORT_SYMBOL_GPL(watchdog_init_timeout);

+static int watchdog_reboot_notifier(struct notifier_block *nb, + unsigned long code, void *data) +{ + struct watchdog_device *wdd; + + wdd = container_of(nb, struct watchdog_device, reboot_nb); + if (code == SYS_DOWN || code == SYS_HALT) { + if (watchdog_active(wdd)) { + int ret; + + ret = wdd->ops->stop(wdd); + if (ret) + return NOTIFY_BAD; + } + } + + return NOTIFY_DONE; +} + static int watchdog_restart_notifier(struct notifier_block *nb, unsigned long action, void *data) { @@ -235,6 +254,19 @@ static int __watchdog_register_device(st } }

+ if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) { + wdd->reboot_nb.notifier_call = watchdog_reboot_notifier; + + ret = register_reboot_notifier(&wdd->reboot_nb); + if (ret) { + pr_err("watchdog%d: Cannot register reboot notifier (%d)\n", + wdd->id, ret); + watchdog_dev_unregister(wdd); + ida_simple_remove(&watchdog_ida, id); + return ret; + } + } + if (wdd->ops->restart) { wdd->restart_nb.notifier_call = watchdog_restart_notifier;

@@ -289,6 +321,9 @@ static void __watchdog_unregister_device if (wdd->ops->restart) unregister_restart_handler(&wdd->restart_nb);

+ if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) + unregister_reboot_notifier(&wdd->reboot_nb); + watchdog_dev_unregister(wdd); ida_simple_remove(&watchdog_ida, wdd->id); } --- a/drivers/watchdog/watchdog_dev.c~watchdog-fix-uaf-in-reboot-notifier-handling-in-watchdog-core-code +++ a/drivers/watchdog/watchdog_dev.c @@ -38,7 +38,6 @@ #include <linux/miscdevice.h> /* For handling misc devices */ #include <linux/module.h> /* For module stuff/... */ #include <linux/mutex.h> /* For mutexes */ -#include <linux/reboot.h> /* For reboot notifier */ #include <linux/slab.h> /* For memory functions */ #include <linux/types.h> /* For standard types (like size_t) */ #include <linux/watchdog.h> /* For watchdog specific items */ @@ -1097,25 +1096,6 @@ static void watchdog_cdev_unregister(str put_device(&wd_data->dev); }

-static int watchdog_reboot_notifier(struct notifier_block *nb, - unsigned long code, void *data) -{ - struct watchdog_device *wdd; - - wdd = container_of(nb, struct watchdog_device, reboot_nb); - if (code == SYS_DOWN || code == SYS_HALT) { - if (watchdog_active(wdd)) { - int ret; - - ret = wdd->ops->stop(wdd); - if (ret) - return NOTIFY_BAD; - } - } - - return NOTIFY_DONE; -} - /* * watchdog_dev_register: register a watchdog device * @wdd: watchdog device @@ -1134,22 +1114,8 @@ int watchdog_dev_register(struct watchdo return ret;

ret = watchdog_register_pretimeout(wdd); - if (ret) { + if (ret) watchdog_cdev_unregister(wdd); - return ret; - } - - if (test_bit(WDOG_STOP_ON_REBOOT, &wdd->status)) { - wdd->reboot_nb.notifier_call = watchdog_reboot_notifier; - - ret = devm_register_reboot_notifier(&wdd->wd_data->dev, - &wdd->reboot_nb); - if (ret) { - pr_err("watchdog%d: Cannot register reboot notifier (%d)\n", - wdd->id, ret); - watchdog_dev_unregister(wdd); - } - }

return ret; } _

Patches currently in -mm which might be from vdronov@redhat.com are