From 033bc52bb6190393c8eed80925fa78cc35b40c6d Mon Sep 17 00:00:00 2001
From: Tom Tromey <tromey@adacore.com>
Date: Wed, 16 Aug 2023 11:29:19 -0600
Subject: [PATCH] Avoid buffer overflow in ada_decode

A bug report pointed out a buffer overflow in ada_decode, which Keith
helpfully analyzed.  ada_decode had a logic error when the input was
all digits.  While this isn't valid -- and would probably only appear
in fuzzer tests -- it still should be handled properly.

This patch adds a missing bounds check.  Tested with the self-tests in
an asan build.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30639
Reviewed-by: Keith Seitz <keiths@redhat.com>
---
 gdb/ada-lang.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index 0c2d4fc..1ff74ca 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -1184,7 +1184,7 @@ ada_decode (const char *encoded)
         i -= 1;
       if (i > 1 && encoded[i] == '_' && encoded[i - 1] == '_')
         len0 = i - 1;
-      else if (encoded[i] == '$')
+      else if (i >= 0 && encoded[i] == '$')
         len0 = i;
     }
 
-- 
2.33.0

