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Date: Tue, 17 Nov 2015 16:52:51 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: Piotr Kwapulinski <kwapulinski.piotr@...il.com> Cc: mhocko@...e.com, oleg@...hat.com, cmetcalf@...hip.com, mszeredi@...e.cz, viro@...iv.linux.org.uk, dave@...olabs.net, kirill.shutemov@...ux.intel.com, n-horiguchi@...jp.nec.com, aarcange@...hat.com, iamjoonsoo.kim@....com, jack@...e.cz, xiexiuqi@...wei.com, vbabka@...e.cz, Vineet.Gupta1@...opsys.com, riel@...hat.com, gang.chen.5i5j@...il.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCH] mm/mmap.c: remove incorrect MAP_FIXED flag comparison from mmap_region On Tue, 17 Nov 2015 18:26:38 +0100 Piotr Kwapulinski <kwapulinski.piotr@...il.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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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