From a7770ae194569e96a93c48aceb304edded9cc648 Mon Sep 17 00:00:00 2001 From: Jean Delvare Date: Sat, 3 Feb 2018 11:25:20 +0100 Subject: [PATCH] firmware: dmi_scan: Fix handling of empty DMI strings 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 Fixes: 79da4721117f ("x86: fix DMI out of memory problems") Cc: Parag Warudkar Cc: Ingo Molnar Cc: Thomas Gleixner --- drivers/firmware/dmi_scan.c | 22 +++++++++------------- 1 file changed, 9 insertions(+), 13 deletions(-) diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c index 8cd5db6691b2..a7072e7880ee 100644 --- a/drivers/firmware/dmi_scan.c +++ b/drivers/firmware/dmi_scan.c @@ -18,7 +18,7 @@ EXPORT_SYMBOL_GPL(dmi_kobj); * 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 u32 dmi_ver __initdata; static u32 dmi_len; @@ -39,25 +39,21 @@ 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) -- 2.30.2