linux-kernel - [PATCH] uprobes/x86: remove the wrong WARN_ON() in uprobe_init

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Date:   Fri, 18 May 2018 18:27:39 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        syzbot <syzbot+30d675e3ca03c1c351e7@...kaller.appspotmail.com>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: [PATCH] uprobes/x86: remove the wrong WARN_ON() in uprobe_init_insn()

insn_get_length() has the side-effect of processing the entire instruction
but only if it was decoded successfully, otherwise insn_complete() can fail
and in this case we need to just return an error without warning.

Reported-by: syzbot+30d675e3ca03c1c351e7@...kaller.appspotmail.com
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
 arch/x86/kernel/uprobes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 85c7ef2..efd7ee9 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -293,7 +293,7 @@ static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool
 	insn_init(insn, auprobe->insn, sizeof(auprobe->insn), x86_64);
 	/* has the side-effect of processing the entire instruction */
 	insn_get_length(insn);
-	if (WARN_ON_ONCE(!insn_complete(insn)))
+	if (!insn_complete(insn))
 		return -ENOEXEC;
 
 	if (is_prefix_bad(insn))
-- 
2.5.0