linux-kernel - [PATCH] x86, mce: Fix stack out-of-bounds write in mce-inject.c:flags

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Message-ID: <20180427163707.ktaiysvbk3yhk4wm@agluck-desk>
Date:   Fri, 27 Apr 2018 09:37:08 -0700
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        linux-edac@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86, mce: Fix stack out-of-bounds write in
 mce-inject.c:flags_read()

Each of the strings that we want to put into the buf[MAX_FLAG_OPT_SIZE]
in flags_read() is two characters. But the sprintf() adds a trailing newline
and will add a terminating NUL byte. So MAX_FLAG_OPT_SIZE needs to be 4.

Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Tony Luck <tony.luck@...el.com>

---

diff --git a/arch/x86/kernel/cpu/mcheck/mce-inject.c b/arch/x86/kernel/cpu/mcheck/mce-inject.c
index 475cb4f5f14f..c805a06e14c3 100644
--- a/arch/x86/kernel/cpu/mcheck/mce-inject.c
+++ b/arch/x86/kernel/cpu/mcheck/mce-inject.c
@@ -48,7 +48,7 @@ static struct dentry *dfs_inj;
 
 static u8 n_banks;
 
-#define MAX_FLAG_OPT_SIZE	3
+#define MAX_FLAG_OPT_SIZE	4
 #define NBCFG			0x44
 
 enum injection_type {