Subject: + vsprintf-bug-on-%n.patch added to -mm tree
To: keescook@xxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Mon, 27 Jan 2014 15:10:45 -0800
The patch titled
Subject: vsprintf: BUG on %n
has been added to the -mm tree. Its filename is
vsprintf-bug-on-%n.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/vsprintf-bug-on-%n.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/vsprintf-bug-on-%n.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Kees Cook <keescook@xxxxxxxxxxxx>
Subject: vsprintf: BUG on %n
Now that there has been a full release of the kernel, and all users of %n
have been dropped, switch to %n use triggering a BUG. Ignoring arguments
could be used to assist in information leaks if an arbitrary format string
was under the control of an attacker.
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/vsprintf.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
diff -puN lib/vsprintf.c~vsprintf-bug-on-%n lib/vsprintf.c
--- a/lib/vsprintf.c~vsprintf-bug-on-%n
+++ a/lib/vsprintf.c
@@ -1735,15 +1735,12 @@ int vsnprintf(char *buf, size_t size, co
case FORMAT_TYPE_NRCHARS: {
/*
* Since %n poses a greater security risk than
- * utility, ignore %n and skip its argument.
+ * utility, it should not be implemented. Instead,
+ * BUG when encountering %n, since there are no
+ * legitimate users and skipping arguments could
+ * assist information leak attacks.
*/
- void *skip_arg;
-
- WARN_ONCE(1, "Please remove ignored %%n in '%s'\n",
- old_fmt);
-
- skip_arg = va_arg(args, void *);
- break;
+ BUG();
}
default:
_
Patches currently in -mm which might be from keescook@xxxxxxxxxxxx are
origin.patch
vsprintf-bug-on-%n.patch
lib-vsprintf-add-%pt-format-specifier.patch
binfmt_elfc-use-get_random_int-to-fix-entropy-depleting.patch
linux-next.patch
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