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authorJean Delvare <jdelvare@suse.de>2015-03-20 09:59:47 +0100
committerMatt Fleming <matt.fleming@intel.com>2015-03-27 10:53:46 +0000
commitbfbaafae8519d82d10da6abe75f5766dd5b20475 (patch)
treed876c1735a8ea9718a3c6f5e122d5aee91547812 /drivers
parent6d9ff473317245e3e5cd9922b4520411c2296388 (diff)
firmware: dmi_scan: Prevent dmi_num integer overflow
dmi_num is a u16, dmi_len is a u32, so this construct: dmi_num = dmi_len / 4; would result in an integer overflow for a DMI table larger than 256 kB. I've never see such a large table so far, but SMBIOS 3.0 makes it possible so maybe we'll see such tables in the future. So instead of faking a structure count when the entry point does not provide it, adjust the loop condition in dmi_table() to properly deal with the case where dmi_num is not set. This bug was introduced with the initial SMBIOS 3.0 support in commit fc43026278b2 ("dmi: add support for SMBIOS 3.0 64-bit entry point"). Signed-off-by: Jean Delvare <jdelvare@suse.de> Cc: Matt Fleming <matt.fleming@intel.com> Cc: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org> Cc: <stable@vger.kernel.org> Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/firmware/dmi_scan.c22
1 files changed, 7 insertions, 15 deletions
diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
index 69fac068669f..2eebd28b4c40 100644
--- a/drivers/firmware/dmi_scan.c
+++ b/drivers/firmware/dmi_scan.c
@@ -86,10 +86,13 @@ static void dmi_table(u8 *buf, u32 len, int num,
int i = 0;
/*
- * Stop when we see all the items the table claimed to have
- * OR we run off the end of the table (also happens)
+ * Stop when we have seen all the items the table claimed to have
+ * (SMBIOS < 3.0 only) OR we reach an end-of-table marker OR we run
+ * off the end of the table (should never happen but sometimes does
+ * on bogus implementations.)
*/
- while ((i < num) && (data - buf + sizeof(struct dmi_header)) <= len) {
+ while ((!num || i < num) &&
+ (data - buf + sizeof(struct dmi_header)) <= len) {
const struct dmi_header *dm = (const struct dmi_header *)data;
/*
@@ -529,21 +532,10 @@ static int __init dmi_smbios3_present(const u8 *buf)
if (memcmp(buf, "_SM3_", 5) == 0 &&
buf[6] < 32 && dmi_checksum(buf, buf[6])) {
dmi_ver = get_unaligned_be16(buf + 7);
+ dmi_num = 0; /* No longer specified */
dmi_len = get_unaligned_le32(buf + 12);
dmi_base = get_unaligned_le64(buf + 16);
- /*
- * The 64-bit SMBIOS 3.0 entry point no longer has a field
- * containing the number of structures present in the table.
- * Instead, it defines the table size as a maximum size, and
- * relies on the end-of-table structure type (#127) to be used
- * to signal the end of the table.
- * So let's define dmi_num as an upper bound as well: each
- * structure has a 4 byte header, so dmi_len / 4 is an upper
- * bound for the number of structures in the table.
- */
- dmi_num = dmi_len / 4;
-
if (dmi_walk_early(dmi_decode) == 0) {
pr_info("SMBIOS %d.%d present.\n",
dmi_ver >> 8, dmi_ver & 0xFF);