[PATCH] mm: actually remap enough memory

[Grazvydas Ignotas <notasas@gmail.com>]

For whatever reason, generic_access_phys() only remaps one page, but
actually allows to access arbitrary size. It's quite easy to trigger
large reads, like printing out large structure with gdb, which leads to
a crash. Fix it by remapping correct size.

Fixes: 28b2ee20c7cb ("access_process_vm device memory infrastructure")
Cc: stable@vger.kernel.org
Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
---
 mm/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index cd62019..a53df67 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3829,7 +3829,7 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
 	if (follow_phys(vma, addr, write, &prot, &phys_addr))
 		return -EINVAL;
 
-	maddr = ioremap_prot(phys_addr, PAGE_SIZE, prot);
+	maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot);
 	if (write)
 		memcpy_toio(maddr + offset, buf, len);
 	else
-- 
1.9.1

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