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authorVladis Dronov <vdronov@redhat.com>2020-01-08 15:53:47 +0300
committerWim Van Sebroeck <wim@linux-watchdog.org>2020-01-27 17:55:46 +0300
commit69503e585192fdd84b240f18a0873d20e18a2e0a (patch)
treebda91263004f0eef925629615c19898b005eec4b /drivers/watchdog/watchdog_dev.c
parentb1301b9022e9769f3228a353a83bb9623c0f6e41 (diff)
downloadlinux-69503e585192fdd84b240f18a0873d20e18a2e0a.tar.xz
watchdog: fix UAF in reboot notifier handling in watchdog core code
After the 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 UAF 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 ffff91316f91ab28 esb_dev.watchdog_device.reboot_nb memory is freed here ^^^ ts# ...woken up [ 181.459010] devres:rel_nodes: dev ffff913171781000 data ffff913174a1dae8 [ 181.460195] devm_unreg_reboot_notifier: res ffff913174a1dae8 nb ffff91316f91ab78 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 ffffffff9c6d50c0 [ 229.943080] notifier_call_chain: nb ffffffff9c6d50c0 nb->next 6b6b6b6b6b6b6b6b [ 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: 00000000000008b3 [ 229.972929] RDX: 0000000000000000 RSI: 0000000000000096 RDI: ffffffff9ccc46ac [ 229.975028] RBP: 0000000000000001 R08: 0000000000000000 R09: 00000000000008b3 [ 229.977039] R10: 0000000000000001 R11: ffffffff9c26c740 R12: 0000000000000000 [ 229.979155] R13: 6b6b6b6b6b6b6b6b R14: 0000000000000000 R15: 00000000fffffffa ... slub_debug=FZP 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! exitcode=0x0000000b 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. Fixes: 44ea39420fc9 ("drivers/watchdog: make use of devm_register_reboot_notifier()") Cc: stable@vger.kernel.org # v4.15+ Signed-off-by: Vladis Dronov <vdronov@redhat.com> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Link: https://lore.kernel.org/r/20200108125347.6067-1-vdronov@redhat.com Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Diffstat (limited to 'drivers/watchdog/watchdog_dev.c')
-rw-r--r--drivers/watchdog/watchdog_dev.c36
1 files changed, 1 insertions, 35 deletions
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 4b2a85438478..8b5c742f24e8 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/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(struct watchdog_device *wdd)
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 watchdog_device *wdd)
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;
}