3.16.57-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Jean Delvare <jdelvare@xxxxxxx>
commit a7770ae194569e96a93c48aceb304edded9cc648 upstream.
The handling of empty DMI strings looks quite broken to me:
* Strings from 1 to 7 spaces are not considered empty.
* True empty DMI strings (string index set to 0) are not considered
empty, and result in allocating a 0-char string.
* Strings with invalid index also result in allocating a 0-char
string.
* Strings starting with 8 spaces are all considered empty, even if
non-space characters follow (sounds like a weird thing to do, but
I have actually seen occurrences of this in DMI tables before.)
* Strings which are considered empty are reported as 8 spaces,
instead of being actually empty.
Some of these issues are the result of an off-by-one error in memcmp,
the rest is incorrect by design.
So let's get it square: missing strings and strings made of only
spaces, regardless of their length, should be treated as empty and
no memory should be allocated for them. All other strings are
non-empty and should be allocated.
Signed-off-by: Jean Delvare <jdelvare@xxxxxxx>
Fixes: 79da4721117f ("x86: fix DMI out of memory problems")
Cc: Parag Warudkar <parag.warudkar@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
drivers/firmware/dmi_scan.c | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -15,7 +15,7 @@
* of and an antecedent to, SMBIOS, which stands for System
* Management BIOS. See further: http://www.dmtf.org/standards
*/
-static const char dmi_empty_string[] = " ";
+static const char dmi_empty_string[] = "";
static u16 __initdata dmi_ver;
/*
@@ -36,25 +36,21 @@ static int dmi_memdev_nr;
static const char * __init dmi_string_nosave(const struct dmi_header *dm, u8 s)
{
const u8 *bp = ((u8 *) dm) + dm->length;
+ const u8 *nsp;
if (s) {
- s--;
- while (s > 0 && *bp) {
+ while (--s > 0 && *bp)
bp += strlen(bp) + 1;
- s--;
- }
- if (*bp != 0) {
- size_t len = strlen(bp)+1;
- size_t cmp_len = len > 8 ? 8 : len;
-
- if (!memcmp(bp, dmi_empty_string, cmp_len))
- return dmi_empty_string;
+ /* Strings containing only spaces are considered empty */
+ nsp = bp;
+ while (*nsp == ' ')
+ nsp++;
+ if (*nsp != '\0')
return bp;
- }
}
- return "";
+ return dmi_empty_string;
}
static const char * __init dmi_string(const struct dmi_header *dm, u8 s)
