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.shevche...@intel.com>
Intel Finland Oy
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