[PATCH] mm/nommu.c: add additional check for vread() just like vwrite()has done.

[Chen Gang]

Since vwrite() has already check whether overflow, as a pair function,
vread() also need do the same thing.

Since vwrite() check the source buffer address, vread() should check
the destination buffer address.


Signed-off-by: Chen Gang <gang.chen@xxxxxxxxxxx>
---
 mm/nommu.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/mm/nommu.c b/mm/nommu.c
index 886e07c..0614ee1 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -282,6 +282,10 @@ EXPORT_SYMBOL(vmalloc_to_pfn);
 
 long vread(char *buf, char *addr, unsigned long count)
 {
+	/* Don't allow overflow */
+	if ((unsigned long) buf + count < count)
+		count = -(unsigned long) buf;
+
 	memcpy(buf, addr, count);
 	return count;
 }
-- 
1.7.7.6
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