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hw/smbios: report error if table size is too large

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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 <imammedo@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200923133804.2089190-3-berrange@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Daniel P. Berrangé 2020-09-23 14:38:03 +01:00 committed by Michael S. Tsirkin
parent bb99f4772f
commit 10c3666658
1 changed files with 14 additions and 0 deletions
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14
hw/smbios/smbios.c
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@ -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);
}
}