[PATCH] avoid buffer underflow in errfinish()

CHECK_STACK_DEPTH checks if errordata_stack_depth is negative.
Move the dereference of &errordata[errordata_stack_depth] after
the check to avoid out-of-bounds read.
---
src/backend/utils/error/elog.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 3a211bf..47a0a8b 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -393,13 +393,15 @@ void
errfinish(int dummy,...)
{
ErrorData *edata = &errordata[errordata_stack_depth];
- int elevel = edata->elevel;
+ int elevel;
MemoryContext oldcontext;
ErrorContextCallback *econtext;

recursion_depth++;
CHECK_STACK_DEPTH();

+ elevel = edata->elevel;
+
/*
* Do processing in ErrorContext, which we hope has enough reserved space
* to report an error.
--
1.7.10.4