Messages in this thread | | | Date | Tue, 17 Nov 2015 16:52:51 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region |
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On Tue, 17 Nov 2015 18:26:38 +0100 Piotr Kwapulinski <kwapulinski.piotr@gmail.com> wrote:
> The following flag comparison in mmap_region is not fully correct: > > if (!(vm_flags & MAP_FIXED)) > > The vm_flags should not be compared with MAP_FIXED (0x10). It is a bit > confusing. This condition is almost always true since VM_MAYREAD (0x10) > flag is almost always set by default. This patch removes this condition. > > ... > > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -1547,13 +1547,6 @@ unsigned long mmap_region(struct file *file, unsigned long addr, > if (!may_expand_vm(mm, len >> PAGE_SHIFT)) { > unsigned long nr_pages; > > - /* > - * MAP_FIXED may remove pages of mappings that intersects with > - * requested mapping. Account for the pages it would unmap. > - */ > - if (!(vm_flags & MAP_FIXED)) > - return -ENOMEM; > - > nr_pages = count_vma_pages_range(mm, addr, addr + len); > > if (!may_expand_vm(mm, (len >> PAGE_SHIFT) - nr_pages))
That looks simpler.
However the changelog doesn't describe the end-user visible effects of the bug, as changelogs should always do. Presumably this is causing incorrect ENOMEM reporting due to RLIMIT_AS being exceeded, but this isn't very specific.
So can you please fill in the details here? Such info is needed when deciding which kernel version(s) need the fix.
Thanks.
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