Patch "coredump: fix race condition between mmget_not_zero()/get_task_mm() and core dumping" has been added to the 4.4-stable tree
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Greg KH
maintainerQuoted 3 lines · Michal Hocko
Please note that I have posted my backport today
http://lkml.kernel.org/r/[email protected] and it differs from this one. Please have a look!
Ah, good point, I just noticed that. Ben, any thoughts as to the difference?
thanks,
greg k-h
Quoted 7 lines · Greg KH
Quoted 3 lines · Michal Hocko
Please note that I have posted my backport today
http://lkml.kernel.org/r/[email protected] and it differs from this one. Please have a look!Ah, good point, I just noticed that. Ben, any thoughts as to the difference?
- The additional fix in binder makes sense to me, and is also needed in 4.9. I'm not sure why I missed it.
- I don't understand why collapse_huge_range() needs to be fixed, but then I really don't understand the khugepaged code at all! So I would trust Michal on this.
- The userfaultfd fixes look different because I picked "userfaultfd:
don't pin the user memory in userfaultfd_file_create()" first and Michal did not. I don't think it makes sense to be calling mmget_still_valid() in these functions if they don't use mmget_not_zero() or similar. But again, Michal is the expert here.
Ben.
Signature · 3 lines
Ben Hutchings, Software Developer Codethink Ltd
https://www.codethink.co.uk/ Dale House, 35 Dale Street
Manchester, M1 2HF, United KingdomOn Tue 04-06-19 16:51:38, Ben Hutchings wrote:
[...]
Quoted 3 lines
- I don't understand why
collapse_huge_range()needs to be fixed, but then I really don't understand the khugepaged code at all! So I would trust Michal on this.
To be honest, I am not really sure myself here. But we are using a remote mm there and I do not see anything that would prevent from racing with exit/coredump. Maybe I am wrong. Let's wait for Andrea for his review feedback. This patch is quite tricky for the stable backport.
Thanks!
Signature · 2 lines
Michal Hocko SUSE Labs
Quoted 10 lines · Michal Hocko
On Tue 04-06-19 16:51:38, Ben Hutchings wrote:
[...]Quoted 3 lines
- I don't understand why
collapse_huge_range()needs to be fixed, but then I really don't understand the khugepaged code at all! So I would trust Michal on this.To be honest, I am not really sure myself here. But we are using a remote mm there and I do not see anything that would prevent from racing with exit/coredump. Maybe I am wrong. Let's wait for Andrea for his review feedback. This patch is quite tricky for the stable backport.
So, Greg, it seems like you should drop this from the current stable round.
Ben.
Signature · 3 lines
Ben Hutchings, Software Developer Codethink Ltd
https://www.codethink.co.uk/ Dale House, 35 Dale Street
Manchester, M1 2HF, United KingdomGreg KH
maintainerQuoted 7 lines · Ben Hutchings
Quoted 6 lines · Michal Hocko
On Tue 04-06-19 16:51:38, Ben Hutchings wrote:
[...]Quoted 3 lines
- I don't understand why
collapse_huge_range()needs to be fixed, but then I really don't understand the khugepaged code at all! So I would trust Michal on this.
Quoted 7 lines
Quoted 4 lines
To be honest, I am not really sure myself here. But we are using a remote mm there and I do not see anything that would prevent from racing with exit/coredump. Maybe I am wrong. Let's wait for Andrea for his review feedback. This patch is quite tricky for the stable backport.
So, Greg, it seems like you should drop this from the current stable round.
Ok, will do, thanks.
greg k-h