| Message ID | 20200108125347.6067-1-vdronov@redhat.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | watchdog: fix UAF in reboot notifier handling in watchdog core code | expand |
On Wed, Jan 08, 2020 at 01:53:47PM +0100, Vladis Dronov wrote: > 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> > --- > drivers/watchdog/watchdog_core.c | 35 +++++++++++++++++++++++++++++++ > drivers/watchdog/watchdog_dev.c | 36 +------------------------------- > 2 files changed, 36 insertions(+), 35 deletions(-) > > diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c > index 21e8085b848b..861daf4f37b2 100644 > --- a/drivers/watchdog/watchdog_core.c > +++ b/drivers/watchdog/watchdog_core.c > @@ -147,6 +147,25 @@ int watchdog_init_timeout(struct watchdog_device *wdd, > } > 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(struct watchdog_device *wdd) > } > } > > + 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(struct watchdog_device *wdd) > 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); > } > 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; > } > -- > 2.20.1 >
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c index 21e8085b848b..861daf4f37b2 100644 --- a/drivers/watchdog/watchdog_core.c +++ b/drivers/watchdog/watchdog_core.c @@ -147,6 +147,25 @@ int watchdog_init_timeout(struct watchdog_device *wdd, } 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(struct watchdog_device *wdd) } } + 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(struct watchdog_device *wdd) 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); } 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; }
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> --- drivers/watchdog/watchdog_core.c | 35 +++++++++++++++++++++++++++++++ drivers/watchdog/watchdog_dev.c | 36 +------------------------------- 2 files changed, 36 insertions(+), 35 deletions(-)