ACK: [SRU][Cosmic][v2][PATCH 0/2] Fixes for LP:1792195

[Khaled Elmously]

On 2018-10-16 14:05:21 , Joseph Salisbury wrote:
> == SRU Justification ==
> IBM is requesting these commits in bionic and cosmic.  This bug fix
> also depends on commit 7acf50e4efa6, which was SRU'd in bug 1792102.
> 
> Description of bug:
> GPFS mmfsd daemon is mapping shared tracing buffer(allocated from kernel
> driver using vmalloc) and then writing trace records from user space threads
> in parallel. While the SIGBUS happened, the access virtual memory address
> is in the mapped range, no overflow on access.
> 
> The root cause is that for PTEs created by a driver at mmap time (ie, that
> aren't created dynamically at fault time), it's not legit for ptep_set_access_flags()
> to make them invalid even temporarily. A concurrent access while they are
> invalid will be unable to service the page fault and will cause as SIGBUS.
> 
> == Fixes ==
> bd0dbb73e013 ("powerpc/mm/books3s: Add new pte bit to mark pte temporarily invalid.")
> f08d08f3db55 ("powerpc/mm/radix: Only need the Nest MMU workaround for R -> RW transition")
> 
> == Regression Potential ==
> Low.  Limited to powerpc.
> 
> == Test Case ==
> A test kernel was built with these patches and tested by IBM.
> IBM states the test kernel resolved the bug.
> 
> 
> Aneesh Kumar K.V (2):
>   powerpc/mm/books3s: Add new pte bit to mark pte temporarily invalid.
>   powerpc/mm/radix: Only need the Nest MMU workaround for R -> RW
>     transition
> 
>  arch/powerpc/include/asm/book3s/64/pgtable.h | 18 +++++++++++++++++-
>  arch/powerpc/mm/pgtable-radix.c              |  8 +++++---
>  2 files changed, 22 insertions(+), 4 deletions(-)
>

Acked-by: Khalid Elmously <khalid.elmously at canonical.com>