Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes

2017-10-05 Thread Will Deacon
On Tue, Oct 03, 2017 at 02:36:42AM -0400, Jon Masters wrote: > On 09/29/2017 04:56 AM, Will Deacon wrote: > > > The full fix isn't just cosmetic; it's also addressing the wider problem > > of unannotated racing page table accesses outside of the specific failure > > case we've run into. > > Let u

Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes

2017-10-02 Thread Jon Masters
On 09/29/2017 04:56 AM, Will Deacon wrote: > The full fix isn't just cosmetic; it's also addressing the wider problem > of unannotated racing page table accesses outside of the specific failure > case we've run into. Let us know if there are additional tests we should be running on the Red Hat en

Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes

2017-09-29 Thread Will Deacon
[+ Timur] On Thu, Sep 28, 2017 at 03:38:00PM -0400, Jon Masters wrote: > On 09/27/2017 11:49 AM, Will Deacon wrote: > > > The moral of the story is that read-after-read (same address) ordering > > *only* > > applies if READ_ONCE is used consistently. This means we need to fix page > > table dere

Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes

2017-09-28 Thread Jon Masters
On 09/27/2017 11:49 AM, Will Deacon wrote: > The moral of the story is that read-after-read (same address) ordering *only* > applies if READ_ONCE is used consistently. This means we need to fix page > table dereferences in the core code as well as the arch code to avoid this > problem. The two RFC

Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes

2017-09-28 Thread Richard Ruigrok
On 9/27/2017 9:49 AM, Will Deacon wrote: > Hi, > > We recently had a crash report[1] on arm64 that involved a bad dereference > in the page_vma_mapped code during ext4 writeback with THP active. I can > reproduce this on -rc2: > > [ 254.032812] PC is at check_pte+0x20/0x170 > [ 254.032948] LR i

Re: [RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes

2017-09-27 Thread Yury Norov
On Wed, Sep 27, 2017 at 04:49:27PM +0100, Will Deacon wrote: > Hi, > > We recently had a crash report[1] on arm64 that involved a bad dereference > in the page_vma_mapped code during ext4 writeback with THP active. I can > reproduce this on -rc2: > > [ 254.032812] PC is at check_pte+0x20/0x170 >

[RFC PATCH 0/2] Missing READ_ONCE in core and arch-specific pgtable code leading to crashes

2017-09-27 Thread Will Deacon
Hi, We recently had a crash report[1] on arm64 that involved a bad dereference in the page_vma_mapped code during ext4 writeback with THP active. I can reproduce this on -rc2: [ 254.032812] PC is at check_pte+0x20/0x170 [ 254.032948] LR is at page_vma_mapped_walk+0x2e0/0x540 [...] [ 254.036114