linux-kernel - [PATCH v2 1/9] objtool: Do not assume order of parent/child functions

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Message-Id: <20200521165641.15940-2-kristen@linux.intel.com>
Date:   Thu, 21 May 2020 09:56:32 -0700
From:   Kristen Carlson Accardi <kristen@...ux.intel.com>
To:     keescook@...omium.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     arjan@...ux.intel.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        rick.p.edgecombe@...el.com,
        Kristen Carlson Accardi <kristen@...ux.intel.com>
Subject: [PATCH v2 1/9] objtool: Do not assume order of parent/child functions

If a .cold function is examined prior to it's parent, the link
to the parent/child function can be overwritten when the parent
is examined. Only update pfunc and cfunc if they were previously
nil to prevent this from happening.

Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 tools/objtool/elf.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index c4857fa3f1d1..b998c853a1f0 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -408,7 +408,13 @@ static int read_symbols(struct elf *elf)
 			size_t pnamelen;
 			if (sym->type != STT_FUNC)
 				continue;
-			sym->pfunc = sym->cfunc = sym;
+
+			if (sym->pfunc == NULL)
+				sym->pfunc = sym;
+
+			if (sym->cfunc == NULL)
+				sym->cfunc = sym;
+
 			coldstr = strstr(sym->name, ".cold");
 			if (!coldstr)
 				continue;
-- 
2.20.1