ksm: check for ERR_PTR from follow_page()
in [Kernel]
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From: Rik van Riel on 21 Apr 2010 11:30 On 04/21/2010 06:27 AM, Dan Carpenter wrote: > The follow_page() function can potentially return -EFAULT so I added > checks for this. > > Also I silenced an uninitialized variable warning on my version of gcc > (version 4.3.2). > > Signed-off-by: Dan Carpenter<error27(a)gmail.com> Acked-by: Rik van Riel <riel(a)redhat.com> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Andrea Arcangeli on 21 Apr 2010 13:50 On Wed, Apr 21, 2010 at 11:24:24AM -0400, Rik van Riel wrote: > On 04/21/2010 06:27 AM, Dan Carpenter wrote: > > The follow_page() function can potentially return -EFAULT so I added > > checks for this. > > > > Also I silenced an uninitialized variable warning on my version of gcc > > (version 4.3.2). > > > > Signed-off-by: Dan Carpenter<error27(a)gmail.com> > > Acked-by: Rik van Riel <riel(a)redhat.com> while (!(page = follow_page(vma, start, foll_flags))) { gup only checks for null, so when exactly is follow_page going to return -EFAULT? It's not immediately clear. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Johannes Weiner on 21 Apr 2010 17:00 On Wed, Apr 21, 2010 at 07:46:15PM +0200, Andrea Arcangeli wrote: > On Wed, Apr 21, 2010 at 11:24:24AM -0400, Rik van Riel wrote: > > On 04/21/2010 06:27 AM, Dan Carpenter wrote: > > > The follow_page() function can potentially return -EFAULT so I added > > > checks for this. > > > > > > Also I silenced an uninitialized variable warning on my version of gcc > > > (version 4.3.2). > > > > > > Signed-off-by: Dan Carpenter<error27(a)gmail.com> > > > > Acked-by: Rik van Riel <riel(a)redhat.com> > > while (!(page = follow_page(vma, start, foll_flags))) > { > > gup only checks for null, so when exactly is follow_page going to > return -EFAULT? It's not immediately clear. Check below that loop. If it returns non-null, the first check is whether it IS_ERR(). How about the below? Hannes --- From: Johannes Weiner <hannes(a)cmpxchg.org> Subject: mm: document follow_page() Signed-off-by: Johannes Weiner <hannes(a)cmpxchg.org> --- mm/memory.c | 13 +++++++++++-- 1 files changed, 11 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 833952d..119b7cc 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1227,8 +1227,17 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address, } EXPORT_SYMBOL_GPL(zap_vma_ptes); -/* - * Do a quick page-table lookup for a single page. +/** + * follow_page - look up a page descriptor from a user-virtual address + * @vma: vm_area_struct mapping @address + * @address: virtual address to look up + * @flags: flags modifying lookup behaviour + * + * @flags can have FOLL_ flags set, defined in <linux/mm.h> + * + * Returns the mapped (struct page *), %NULL if no mapping exists, or + * an error pointer if there is a mapping to something not represented + * by a page descriptor (see also vm_normal_page()). */ struct page *follow_page(struct vm_area_struct *vma, unsigned long address, unsigned int flags) -- 1.7.0.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Andrea Arcangeli on 21 Apr 2010 17:00 On Wed, Apr 21, 2010 at 10:53:05PM +0200, Johannes Weiner wrote: > Check below that loop. If it returns non-null, the first check is > whether it IS_ERR(). Indeed. > + * Returns the mapped (struct page *), %NULL if no mapping exists, or > + * an error pointer if there is a mapping to something not represented > + * by a page descriptor (see also vm_normal_page()). where exactly in vm_normal_page? Note I already checked vm_normal_page before sending the prev email and I didn't immediately see. I search return and they all return NULL except the return pfn_to_page(pfn), so is pfn_to_page that returns -EFAULT (the implementations I checked don't but there are plenty that I didn't check...). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Johannes Weiner on 21 Apr 2010 17:20 On Wed, Apr 21, 2010 at 10:58:07PM +0200, Andrea Arcangeli wrote: > On Wed, Apr 21, 2010 at 10:53:05PM +0200, Johannes Weiner wrote: > > + * Returns the mapped (struct page *), %NULL if no mapping exists, or > > + * an error pointer if there is a mapping to something not represented > > + * by a page descriptor (see also vm_normal_page()). > > where exactly in vm_normal_page? Note I already checked vm_normal_page > before sending the prev email and I didn't immediately see. I search > return and they all return NULL except the return pfn_to_page(pfn), so > is pfn_to_page that returns -EFAULT (the implementations I checked > don't but there are plenty that I didn't check...). It's not vm_normal_page() that returns -EFAULT. It is follow_page() that translates NULL from vm_normal_page() into -EFAULT. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.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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