]> git.baikalelectronics.ru Git - kernel.git/commit
powerpc/powernv/idle: Restore IAMR after idle
authorRussell Currey <ruscur@russell.cc>
Thu, 18 Apr 2019 06:51:16 +0000 (16:51 +1000)
committerMichael Ellerman <mpe@ellerman.id.au>
Sun, 21 Apr 2019 13:05:52 +0000 (23:05 +1000)
commit9d53c4f0876cb0ffd1c80cb094ac4a8fa3471289
treea76f2ef8e08c50710ff87b923669f1d06a0d23a0
parent69f6ec45a65e34907fe5c2826a142dfe19c401db
powerpc/powernv/idle: Restore IAMR after idle

Without restoring the IAMR after idle, execution prevention on POWER9
with Radix MMU is overwritten and the kernel can freely execute
userspace without faulting.

This is necessary when returning from any stop state that modifies
user state, as well as hypervisor state.

To test how this fails without this patch, load the lkdtm driver and
do the following:

  $ echo EXEC_USERSPACE > /sys/kernel/debug/provoke-crash/DIRECT

which won't fault, then boot the kernel with powersave=off, where it
will fault. Applying this patch will fix this.

Fixes: c3257c328e1e ("powerpc/mm/radix: Prevent kernel execution of user space")
Cc: stable@vger.kernel.org # v4.10+
Signed-off-by: Russell Currey <ruscur@russell.cc>
Reviewed-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
arch/powerpc/kernel/idle_book3s.S