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Subject[PATCH] vsprintf: protect kernel from panic due to non-canonical pointer dereference
Date
While debugging a separate issue, it was found that an invalid string
pointer could very well contain a non-canical address, such as
0x7665645f63616465. In that case, this line of defense isn't enough
to protect the kernel from crashing due to general protection fault

if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
return "(efault)";

So instead, use kern_addr_valid() to validate the string pointer.

Signed-off-by: Jane Chu <jane.chu@oracle.com>
---
lib/vsprintf.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index c414a8d9f1ea..2e8a9efc7c12 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -695,7 +695,7 @@ static const char *check_pointer_msg(const void *ptr)
if (!ptr)
return "(null)";

- if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
+ if (!kern_addr_valid((unsigned long)ptr))
return "(efault)";

return NULL;
--
2.18.4
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