[PATCH] arm64: ftrace: don't dereference a probably invalid address

[Mark-PK Tsai]

Address in __mcount_loc may be invalid if somthing goes wrong.
On our arm64 platform, the bug in recordmcount make kernel
crash in ftrace_init().

https://lore.kernel.org/lkml/20210607023839.26387-1-mark-pk.tsai@xxxxxxxxxxxx/

Return -EFAULT if we are dealing with out-of-range condition
to prevent dereference the invalid address in ftrace_bug(),
then the kernel can disable ftrace safely for problematic
__mcount_loc.

Signed-off-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx>
---
 arch/arm64/kernel/ftrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index b5d3ddaf69d9..98bec8445a58 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -201,7 +201,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 			preempt_enable();
 
 			if (WARN_ON(!mod))
-				return -EINVAL;
+				return -EFAULT;
 		}
 
 		/*
-- 
2.18.0