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authorLinus Torvalds <torvalds@linux-foundation.org>2008-07-28 17:54:21 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-28 17:54:21 -0700
commit9b79022ca909b66e2cd0cfd9248f832fc165f77f (patch)
treebcd8c3204886fcbc8422aeb482f8e42c0b5b6124
parent34ee55014283a60efa3534c06e010579ffdd3756 (diff)
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Fix 'get_user_pages_fast()' with non-page-aligned start address
Alexey Dobriyan reported trouble with LTP with the new fast-gup code, and Johannes Weiner debugged it to non-page-aligned addresses, where the new get_user_pages_fast() code would do all the wrong things, including just traversing past the end of the requested area due to 'addr' never matching 'end' exactly. This is not a pretty fix, and we may actually want to move the alignment into generic code, leaving just the core code per-arch, but Alexey verified that the vmsplice01 LTP test doesn't crash with this. Reported-and-tested-by: Alexey Dobriyan <adobriyan@gmail.com> Debugged-by: Johannes Weiner <hannes@saeurebad.de> Cc: Nick Piggin <npiggin@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/x86/mm/gup.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index 3085f25b4355..007bb06c7504 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -223,14 +223,17 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int write,
struct page **pages)
{
struct mm_struct *mm = current->mm;
- unsigned long end = start + (nr_pages << PAGE_SHIFT);
- unsigned long addr = start;
+ unsigned long addr, len, end;
unsigned long next;
pgd_t *pgdp;
int nr = 0;
+ start &= PAGE_MASK;
+ addr = start;
+ len = (unsigned long) nr_pages << PAGE_SHIFT;
+ end = start + len;
if (unlikely(!access_ok(write ? VERIFY_WRITE : VERIFY_READ,
- start, nr_pages*PAGE_SIZE)))
+ start, len)))
goto slow_irqon;
/*