From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Jiri Kosina <jkosina@suse.cz>,
Randy Dunlap <rdunlap@infradead.org>,
Fabian Frederick <fabf@skynet.be>,
Bjorn Helgaas <bhelgaas@google.com>,
Ryan Mallon <rmallon@gmail.com>,
Masanari Iida <standby24x7@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] lib/vsprintf.c: Fix potential NULL deref in hex_string
Date: Wed, 28 Jan 2015 16:53:44 +0200 [thread overview]
Message-ID: <1422456824.31903.298.camel@linux.intel.com> (raw)
In-Reply-To: <1422451543-12401-2-git-send-email-linux@rasmusvillemoes.dk>
On Wed, 2015-01-28 at 14:25 +0100, Rasmus Villemoes wrote:
> The helper hex_string() is broken in two ways. First, it doesn't
> increment buf regardless of whether there is room to print, so callers
> such as kasprintf() that try to probe the correct storage to allocate
> will get a too small return value. But even worse, kasprintf() (and
> likely anyone else trying to find the size of the result) pass NULL
> for buf and 0 for size, so we also have end == NULL. But this means
> that the end-1 in hex_string() is (char*)-1, so buf < end-1 is true
> and we get a NULL pointer deref. I double-checked this with a trivial
> kernel module that just did a kasprintf(GFP_KERNEL, "%14ph",
> "CrashBoomBang").
Good catch, though I don't like the implementation of fix.
What about the following?
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 8690798..47b36ddd 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -783,11 +783,20 @@ char *hex_string(char *buf, char *end, u8 *addr,
struct printf_spec spec,
if (spec.field_width > 0)
len = min_t(int, spec.field_width, 64);
- for (i = 0; i < len && buf < end - 1; i++) {
- buf = hex_byte_pack(buf, addr[i]);
+ for (i = 0; i < len; i++) {
+ if (buf < end)
+ *buf = hex_asc_hi(addr[i]);
+ ++buf;
+
+ if (buf < end)
+ *buf = hex_asc_lo(addr[i]);
+ ++buf;
- if (buf < end && separator && i != len - 1)
- *buf++ = separator;
+ if (separator && i != len - 1) {
+ if (buf < end)
+ *buf = separator;
+ ++buf;
+ }
}
return buf;
> Nobody seems to be using %ph with kasprintf, but we might as well fix
> it before it hits someone.
--
Andy Shevchenko <andriy.shevchenko@intel.com>
Intel Finland Oy
next prev parent reply other threads:[~2015-01-28 20:21 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-28 13:25 [PATCH 0/2] Two printf fixes Rasmus Villemoes
2015-01-28 13:25 ` [PATCH 1/2] lib/vsprintf.c: Fix potential NULL deref in hex_string Rasmus Villemoes
2015-01-28 14:53 ` Andy Shevchenko [this message]
2015-01-28 15:49 ` Rasmus Villemoes
2015-01-28 16:43 ` Andy Shevchenko
2015-01-28 13:25 ` [PATCH 2/2] string_helpers: Change semantics of string_escape_mem Rasmus Villemoes
2015-01-28 15:05 ` Andy Shevchenko
2015-01-29 10:03 ` [PATCH v2 0/3] Two printf fixes Rasmus Villemoes
2015-01-29 10:03 ` [PATCH v2 1/3] lib/vsprintf.c: Fix potential NULL deref in hex_string Rasmus Villemoes
2015-01-29 10:43 ` Andy Shevchenko
2015-01-29 10:03 ` [PATCH v2 2/3] lib/string_helpers.c: Refactor string_escape_mem Rasmus Villemoes
2015-01-29 12:12 ` Andy Shevchenko
2015-01-29 13:10 ` Rasmus Villemoes
2015-01-29 13:37 ` Andy Shevchenko
2015-01-29 19:33 ` Jeff Epler
2015-01-30 10:14 ` Andy Shevchenko
2015-01-29 10:03 ` [PATCH v2 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
2015-01-29 13:29 ` Andy Shevchenko
2015-01-29 14:29 ` Rasmus Villemoes
2015-01-30 10:27 ` Andy Shevchenko
2015-01-30 23:39 ` Rasmus Villemoes
2015-02-02 10:56 ` Andy Shevchenko
2015-02-09 23:44 ` [PATCH v3 0/3] Two printf fixes Rasmus Villemoes
2015-02-09 23:44 ` [PATCH v3 1/3] lib/vsprintf.c: Fix potential NULL deref in hex_string Rasmus Villemoes
2015-02-09 23:44 ` [PATCH v3 2/3] lib/string_helpers.c: Refactor string_escape_mem Rasmus Villemoes
2015-02-10 12:16 ` Andy Shevchenko
2015-02-09 23:44 ` [PATCH v3 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
2015-02-10 12:32 ` Andy Shevchenko
2015-02-10 13:02 ` Rasmus Villemoes
2015-02-10 14:22 ` Andy Shevchenko
2015-02-21 1:35 ` Rasmus Villemoes
2015-02-23 12:50 ` Andy Shevchenko
2015-02-23 22:55 ` Rasmus Villemoes
2015-03-02 12:37 ` Andy Shevchenko
2015-03-02 23:03 ` Rasmus Villemoes
2015-03-03 10:26 ` Andy Shevchenko
2015-03-03 23:20 ` [PATCH v4 0/3] Two printf fixes Rasmus Villemoes
2015-03-03 23:20 ` [PATCH v4 1/3] lib/vsprintf.c: Fix potential NULL deref in hex_string Rasmus Villemoes
2015-03-03 23:20 ` [PATCH v4 2/3] lib/string_helpers.c: Refactor string_escape_mem Rasmus Villemoes
2015-03-04 10:51 ` Andy Shevchenko
2015-03-03 23:20 ` [PATCH v4 3/3] lib/string_helpers.c: Change semantics of string_escape_mem Rasmus Villemoes
2015-03-04 11:49 ` Andy Shevchenko
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