Messages in this thread | | | Date | Fri, 7 Jul 2023 12:45:07 -0400 | From | "Liam R. Howlett" <> | Subject | Re: [PATCH stable v6.1] mm/mmap: Fix extra maple tree write |
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* Greg KH <gregkh@linuxfoundation.org> [230707 11:55]: > On Thu, Jul 06, 2023 at 02:51:35PM -0400, Liam R. Howlett wrote: > > commit 0503ea8f5ba73eb3ab13a81c1eefbaf51405385a upstream. > > > > This was inadvertently fixed during the removal of __vma_adjust(). > > > > When __vma_adjust() is adjusting next with a negative value (pushing > > vma->vm_end lower), there would be two writes to the maple tree. The > > first write is unnecessary and uses all allocated nodes in the maple > > state. The second write is necessary but will need to allocate nodes > > since the first write has used the allocated nodes. This may be a > > problem as it may not be safe to allocate at this time, such as a low > > memory situation. Fix the issue by avoiding the first write and only > > write the adjusted "next" VMA. > > Are you sure this is the same git id? The one you reference above is > _VERY_ different from your 2 line change below. > > And the changelog text is not the same.
Yes, but I am not sure I've indicated what happened correctly.
The bug exists in the older __vma_adjust() function, but I removed __vma_adjust() and inadvertently fixed the bug. So the bug doesn't exist upstream *because* of that commit:
0503ea8f5ba7 ("mm/mmap: remove __vma_adjust()")
My comment after the commit id indicates what happened, but the documentation wasn't clear to me on how to specify what happened.
Does this answer your question?
Thanks, Liam
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