From: Daniel P. Berrangé Date: Wed, 23 Sep 2020 13:38:03 +0000 (+0100) Subject: hw/smbios: report error if table size is too large X-Git-Tag: pull-nvme-20201102~84^2~16 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=10c3666658f53c5ec8fd9ec27cdf5c393ff814a0;p=qemu-nvme.git hw/smbios: report error if table size is too large The SMBIOS 2.1 entry point uses a uint16 data type for reporting the total length of the tables. If the user passes -smbios configuration to QEMU that causes the table size to exceed this limit then various bad behaviours result, including - firmware hangs in an infinite loop - firmware triggers a KVM crash on bad memory access - firmware silently discards user's SMBIOS data replacing it with a generic data set. Limiting the size to 0xffff in QEMU avoids triggering most of these problems. There is a remaining bug in SeaBIOS which tries to prepend its own data for table 0, and does not check whether there is sufficient space before attempting this. Reviewed-by: Igor Mammedov Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Daniel P. Berrangé Message-Id: <20200923133804.2089190-3-berrange@redhat.com> Tested-by: Laszlo Ersek Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- diff --git a/hw/smbios/smbios.c b/hw/smbios/smbios.c index d993448087..8b30906e50 100644 --- a/hw/smbios/smbios.c +++ b/hw/smbios/smbios.c @@ -365,6 +365,13 @@ static void smbios_register_config(void) opts_init(smbios_register_config); +/* + * The SMBIOS 2.1 "structure table length" field in the + * entry point uses a 16-bit integer, so we're limited + * in total table size + */ +#define SMBIOS_21_MAX_TABLES_LEN 0xffff + static void smbios_validate_table(MachineState *ms) { uint32_t expect_t4_count = smbios_legacy ? @@ -375,6 +382,13 @@ static void smbios_validate_table(MachineState *ms) expect_t4_count, smbios_type4_count); exit(1); } + + if (smbios_ep_type == SMBIOS_ENTRY_POINT_21 && + smbios_tables_len > SMBIOS_21_MAX_TABLES_LEN) { + error_report("SMBIOS 2.1 table length %zu exceeds %d", + smbios_tables_len, SMBIOS_21_MAX_TABLES_LEN); + exit(1); + } }