4.4-stable review patch. If anyone has any objections, please let me know.
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From: Jean Delvare jdelvare@suse.de
[ Upstream commit a7770ae194569e96a93c48aceb304edded9cc648 ]
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@suse.de Fixes: 79da4721117f ("x86: fix DMI out of memory problems") Cc: Parag Warudkar parag.warudkar@gmail.com Cc: Ingo Molnar mingo@kernel.org Cc: Thomas Gleixner tglx@linutronix.de Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 @@ -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; @@ -44,25 +44,21 @@ 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)