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cpu/hotplug: Fix out-of-bounds read when setting fail state 

Setting invalid value to /sys/devices/system/cpu/cpuX/hotplug/fail
can control `struct cpuhp_step *sp` address, results in the following
global-out-of-bounds read.

Reproducer:

  # echo -2 > /sys/devices/system/cpu/cpu0/hotplug/fail

KASAN report:

  BUG: KASAN: global-out-of-bounds in write_cpuhp_fail+0x2cd/0x2e0
  Read of size 8 at addr ffffffff89734438 by task bash/1941

  CPU: 0 PID: 1941 Comm: bash Not tainted 5.2.0-rc6+ #31
  Call Trace:
   write_cpuhp_fail+0x2cd/0x2e0
   dev_attr_store+0x58/0x80
   sysfs_kf_write+0x13d/0x1a0
   kernfs_fop_write+0x2bc/0x460
   vfs_write+0x1e1/0x560
   ksys_write+0x126/0x250
   do_syscall_64+0xc1/0x390
   entry_SYSCALL_64_after_hwframe+0x49/0xbe
  RIP: 0033:0x7f05e4f4c970

  The buggy address belongs to the variable:
   cpu_hotplug_lock+0x98/0xa0

  Memory state around the buggy address:
   ffffffff89734300: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
   ffffffff89734380: fa fa fa fa 00 00 00 00 00 00 00 00 00 00 00 00
  >ffffffff89734400: 00 00 00 00 fa fa fa fa 00 00 00 00 fa fa fa fa
                                          ^
   ffffffff89734480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
   ffffffff89734500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Add a sanity check for the value written from user space.

Fixes: 1db49484f2 ("smp/hotplug: Hotplug state fail injection")
Signed-off-by: Eiichi Tsukata <devel@etsukata.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: peterz@infradead.org
Link: https://lkml.kernel.org/r/20190627024732.31672-1-devel@etsukata.com
This commit is contained in:
Eiichi Tsukata 2019-06-27 11:47:32 +09:00 committed by Thomas Gleixner
parent 1bf7272028
commit 33d4a5a7a5
1 changed files with 3 additions and 0 deletions
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3
kernel/cpu.c
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@ -1964,6 +1964,9 @@ static ssize_t write_cpuhp_fail(struct device *dev,
if (ret)
return ret;
if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
return -EINVAL;
/*
* Cannot fail STARTING/DYING callbacks.
*/