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Message-Id: <1507517945-27155-1-git-send-email-me@tobin.cc> Date: Mon, 9 Oct 2017 13:59:05 +1100 From: "Tobin C. Harding" <me@...in.cc> To: kernel-hardening@...ts.openwall.com Cc: "Tobin C. Harding" <me@...in.cc>, linux-kernel@...r.kernel.org Subject: [PATCH] lib/vsprintf: add default case to 'i' specifier %pi leaks kernel addresses if incorrectly specified. Currently the printk specifier %pi (%pI) contains a switch statement without a default clause. The %pi specifier requires a subsequent character (4, 6, or S) controlling the output. If the specifier is incomplete the switch statement will fall through and print the variable argument address in hex instead of the value of the argument (as an IP address). If uncaught this leaks kernel addresses into dmesg. We can return an error string to make the bug visible and stop addresses leaking. Add a default clause returning an error string, stops leaking addresses and makes the buggy code Signed-off-by: Tobin C. Harding <me@...in.cc> --- lib/vsprintf.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 86c3385b9eb3..155702f05b14 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -1775,6 +1775,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, default: return string(buf, end, "(invalid address)", spec); }} + default: + return string(buf, end, "(invalid specifier, form: %pi4)", spec); } break; case 'E': -- 2.7.4
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