linux-kernel - [tip: objtool/urgent] objtool: Fix segfault in ignore_unreachable

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Message-ID: <174317038796.14745.5274581486617831611.tip-bot2@tip-bot2>
Date: Fri, 28 Mar 2025 13:59:47 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...nel.org>,
 Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject:
 [tip: objtool/urgent] objtool: Fix segfault in ignore_unreachable_insn()

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     69d41d6dafff0967565b971d950bd10443e4076c
Gitweb:        https://git.kernel.org/tip/69d41d6dafff0967565b971d950bd10443e4076c
Author:        Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate:    Thu, 27 Mar 2025 22:04:21 -07:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Fri, 28 Mar 2025 14:47:02 +01:00

objtool: Fix segfault in ignore_unreachable_insn()

Check 'prev_insn' before dereferencing it.

Fixes: bd841d6154f5 ("objtool: Fix CONFIG_UBSAN_TRAP unreachable warnings")
Reported-by: Arnd Bergmann <arnd@...db.de>
Reported-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/5df4ff89c9e4b9e788b77b0531234ffa7ba03e9e.1743136205.git.jpoimboe@kernel.org

Closes: https://lore.kernel.org/d86b4cc6-0b97-4095-8793-a7384410b8ab@app.fastmail.com
Closes: https://lore.kernel.org/Z-V_rruKY0-36pqA@gmail.com
---
 tools/objtool/check.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 3bf2992..29de170 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4037,7 +4037,7 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 	 * It may also insert a UD2 after calling a __noreturn function.
 	 */
 	prev_insn = prev_insn_same_sec(file, insn);
-	if (prev_insn->dead_end &&
+	if (prev_insn && prev_insn->dead_end &&
 	    (insn->type == INSN_BUG ||
 	     (insn->type == INSN_JUMP_UNCONDITIONAL &&
 	      insn->jump_dest && insn->jump_dest->type == INSN_BUG)))