Re: [PATCH v2 07/20] smbios: avoid mangling user provided tables

[Ani Sinha]

> On 08-Mar-2024, at 22:49, Igor Mammedov <imammedo@redhat.com> wrote:
> 
> On Thu, 7 Mar 2024 09:33:17 +0530
> Ani Sinha <anisinha@redhat.com> wrote:
> 
>>> On 06-Mar-2024, at 12:11, Ani Sinha <anisinha@redhat.com> wrote:
>>> 
>>> 
>>> 
>>> On Tue, 5 Mar 2024, Igor Mammedov wrote:
>>> 
>>>> currently smbios_entry_add() preserves internally '-smbios type='
>>>> options but tables provided with '-smbios file=' are stored directly
>>>> into blob that eventually will be exposed to VM. And then later
>>>> QEMU adds default/'-smbios type' entries on top into the same blob.
>>>> 
>>>> It makes impossible to generate tables more than once, hence
>>>> 'immutable' guard was used.
>>>> Make it possible to regenerate final blob by storing user provided
>>>> blobs into a dedicated area (usr_blobs) and then copy it when
>>>> composing final blob. Which also makes handling of -smbios
>>>> options consistent.
>>>> 
>>>> As side effect of this and previous commits there is no need to
>>>> generate legacy smbios_entries at the time options are parsed.
>>>> Instead compose smbios_entries on demand from  usr_blobs like
>>>> it is done for non-legacy SMBIOS tables.
>>>> 
>>>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
>>>> Tested-by: Fiona Ebner <f.ebner@proxmox.com>  
>>> 
>>> Reviewed-by: Ani Sinha <anisinha@redhat.com>
>>> 
>>>> ---
>>>> hw/smbios/smbios.c | 179 +++++++++++++++++++++++----------------------
>>>> 1 file changed, 92 insertions(+), 87 deletions(-)
>>>> 
>>>> diff --git a/hw/smbios/smbios.c b/hw/smbios/smbios.c
>>>> index c46fc93357..aa2cc5bdbd 100644
>>>> --- a/hw/smbios/smbios.c
>>>> +++ b/hw/smbios/smbios.c
>>>> @@ -57,6 +57,14 @@ static size_t smbios_entries_len;
>>>> static bool smbios_uuid_encoded = true;
>>>> /* end: legacy structures & constants for <= 2.0 machines */
>>>> 
>>>> +/*
>>>> + * SMBIOS tables provided by user with '-smbios file=<foo>' option
>>>> + */
>>>> +uint8_t *usr_blobs;
>>>> +size_t usr_blobs_len;
>>>> +static GArray *usr_blobs_sizes;
>>>> +static unsigned usr_table_max;
>>>> +static unsigned usr_table_cnt;
>>>> 
>>>> uint8_t *smbios_tables;
>>>> size_t smbios_tables_len;
>>>> @@ -67,7 +75,6 @@ static SmbiosEntryPointType smbios_ep_type = 
>>>> SMBIOS_ENTRY_POINT_TYPE_32;
>>>> static SmbiosEntryPoint ep;
>>>> 
>>>> static int smbios_type4_count = 0;
>>>> -static bool smbios_immutable;
>>>> static bool smbios_have_defaults;
>>>> static uint32_t smbios_cpuid_version, smbios_cpuid_features;
>>>> 
>>>> @@ -569,9 +576,8 @@ static void smbios_build_type_1_fields(void)
>>>> 
>>>> uint8_t *smbios_get_table_legacy(uint32_t expected_t4_count, size_t 
>>>> *length)
>>>> {
>>>> -    /* drop unwanted version of command-line file blob(s) */
>>>> -    g_free(smbios_tables);
>>>> -    smbios_tables = NULL;
>>>> +    int i;
>>>> +    size_t usr_offset;
>>>> 
>>>>    /* also complain if fields were given for types > 1 */
>>>>    if (find_next_bit(have_fields_bitmap,
>>>> @@ -581,12 +587,33 @@ uint8_t *smbios_get_table_legacy(uint32_t 
>>>> expected_t4_count, size_t *length)
>>>>        exit(1);
>>>>    }
>>>> 
>>>> -    if (!smbios_immutable) {
>>>> -        smbios_build_type_0_fields();
>>>> -        smbios_build_type_1_fields();
>>>> -        smbios_validate_table(expected_t4_count);
>>>> -        smbios_immutable = true;
>>>> +    g_free(smbios_entries);
>>>> +    smbios_entries_len = sizeof(uint16_t);
>>>> +    smbios_entries = g_malloc0(smbios_entries_len);
>>>> +
>>>> +    for (i = 0, usr_offset = 0; usr_blobs_sizes && i < 
>>>> usr_blobs_sizes->len;
>>>> +         i++)
>>>> +    {
>>>> +        struct smbios_table *table;
>>>> +        struct smbios_structure_header *header;
>>>> +        size_t size = g_array_index(usr_blobs_sizes, size_t, i);
>>>> +
>>>> +        header = (struct smbios_structure_header *)(usr_blobs + 
>>>> usr_offset);
>>>> +        smbios_entries = g_realloc(smbios_entries, smbios_entries_len +
>>>> +                                                   size + sizeof(*table));
>>>> +        table = (struct smbios_table *)(smbios_entries + 
>>>> smbios_entries_len);
>>>> +        table->header.type = SMBIOS_TABLE_ENTRY;
>>>> +        table->header.length = cpu_to_le16(sizeof(*table) + size);
>>>> +        memcpy(table->data, header, size);
>>>> +        smbios_entries_len += sizeof(*table) + size;
>>>> +        (*(uint16_t *)smbios_entries) =
>>>> +            cpu_to_le16(le16_to_cpu(*(uint16_t *)smbios_entries) + 1);  
>>> 
>>> I know this comes from existing code but can you please explain why we add
>>> 1 to it? This is confusing and a comment here would be nice.
>>> 
>>>> +        usr_offset += size;  
>>> 
>>> It would be better if we could add a comment here describing a bit what
>>> this is all about.
>>> 
>>> user blobs are an array of smbios_structure_header entries whereas legacy
>>> tables are an array of smbios_table structures where
>>> smbios_table->data represents the a single user provided table blob in
>>> smbios_structure_header.  
>> 
>> Igor, are you going to send a v3 for this with the comments added?
> 
> I can add comments as a patch on top of series,
> though I'd rather prefer to deprecate all this legacy code
> (along with ISA machine) and just remove it.

The reason why I suggested this is because since you have done so much rework 
on this code, you are probably fresh on the knowledge of how and why the code 
is written the way it is. It might be better to improve the documentation at 
the same time while you are at it while the knowledge is still fresh in your 
mind so that the life is better for the next person who touches this. 

> 
>> 
>>> 
>>>>    }
>>>> +
>>>> +    smbios_build_type_0_fields();
>>>> +    smbios_build_type_1_fields();
>>>> +    smbios_validate_table(expected_t4_count);
>>>>    *length = smbios_entries_len;
>>>>    return smbios_entries;
>>>> }
>>>> @@ -1094,67 +1121,67 @@ void smbios_get_tables(MachineState *ms,
>>>> {
>>>>    unsigned i, dimm_cnt, offset;
>>>> 
>>>> -    /* drop unwanted (legacy) version of command-line file blob(s) */
>>>> -    g_free(smbios_entries);
>>>> -    smbios_entries = NULL;
>>>> +    g_free(smbios_tables);
>>>> +    smbios_tables = g_memdup2(usr_blobs, usr_blobs_len);  
>>> 
>>> Again a comment describing here would be nice as to why memdup is ok.
>>> 
>>>> +    smbios_tables_len = usr_blobs_len;
>>>> +    smbios_table_max = usr_table_max;
>>>> +    smbios_table_cnt = usr_table_cnt;
>>>> 
>>>> -    if (!smbios_immutable) {
>>>> -        smbios_build_type_0_table();
>>>> -        smbios_build_type_1_table();
>>>> -        smbios_build_type_2_table();
>>>> -        smbios_build_type_3_table();
>>>> +    smbios_build_type_0_table();
>>>> +    smbios_build_type_1_table();
>>>> +    smbios_build_type_2_table();
>>>> +    smbios_build_type_3_table();
>>>> 
>>>> -        assert(ms->smp.sockets >= 1);
>>>> +    assert(ms->smp.sockets >= 1);
>>>> 
>>>> -        for (i = 0; i < ms->smp.sockets; i++) {
>>>> -            smbios_build_type_4_table(ms, i);
>>>> -        }
>>>> +    for (i = 0; i < ms->smp.sockets; i++) {
>>>> +        smbios_build_type_4_table(ms, i);
>>>> +    }
>>>> 
>>>> -        smbios_build_type_8_table();
>>>> -        smbios_build_type_11_table();
>>>> +    smbios_build_type_8_table();
>>>> +    smbios_build_type_11_table();
>>>> 
>>>> #define MAX_DIMM_SZ (16 * GiB)
>>>> #define GET_DIMM_SZ ((i < dimm_cnt - 1) ? MAX_DIMM_SZ \
>>>>                                        : ((current_machine->ram_size - 1) 
>>>> % MAX_DIMM_SZ) + 1)
>>>> 
>>>> -        dimm_cnt = QEMU_ALIGN_UP(current_machine->ram_size, MAX_DIMM_SZ) 
>>>> / MAX_DIMM_SZ;
>>>> +    dimm_cnt = QEMU_ALIGN_UP(current_machine->ram_size, MAX_DIMM_SZ) /
>>>> +               MAX_DIMM_SZ;
>>>> 
>>>> -        /*
>>>> -         * The offset determines if we need to keep additional space 
>>>> between
>>>> -         * table 17 and table 19 header handle numbers so that they do
>>>> -         * not overlap. For example, for a VM with larger than 8 TB guest
>>>> -         * memory and DIMM like chunks of 16 GiB, the default space 
>>>> between
>>>> -         * the two tables (T19_BASE - T17_BASE = 512) is not enough.
>>>> -         */
>>>> -        offset = (dimm_cnt > (T19_BASE - T17_BASE)) ? \
>>>> -                 dimm_cnt - (T19_BASE - T17_BASE) : 0;
>>>> +    /*
>>>> +     * The offset determines if we need to keep additional space between
>>>> +     * table 17 and table 19 header handle numbers so that they do
>>>> +     * not overlap. For example, for a VM with larger than 8 TB guest
>>>> +     * memory and DIMM like chunks of 16 GiB, the default space between
>>>> +     * the two tables (T19_BASE - T17_BASE = 512) is not enough.
>>>> +     */
>>>> +    offset = (dimm_cnt > (T19_BASE - T17_BASE)) ? \
>>>> +             dimm_cnt - (T19_BASE - T17_BASE) : 0;
>>>> 
>>>> -        smbios_build_type_16_table(dimm_cnt);
>>>> +    smbios_build_type_16_table(dimm_cnt);
>>>> 
>>>> -        for (i = 0; i < dimm_cnt; i++) {
>>>> -            smbios_build_type_17_table(i, GET_DIMM_SZ);
>>>> -        }
>>>> +    for (i = 0; i < dimm_cnt; i++) {
>>>> +        smbios_build_type_17_table(i, GET_DIMM_SZ);
>>>> +    }
>>>> 
>>>> -        for (i = 0; i < mem_array_size; i++) {
>>>> -            smbios_build_type_19_table(i, offset, mem_array[i].address,
>>>> -                                       mem_array[i].length);
>>>> -        }
>>>> +    for (i = 0; i < mem_array_size; i++) {
>>>> +        smbios_build_type_19_table(i, offset, mem_array[i].address,
>>>> +                                   mem_array[i].length);
>>>> +    }
>>>> 
>>>> -        /*
>>>> -         * make sure 16 bit handle numbers in the headers of tables 19
>>>> -         * and 32 do not overlap.
>>>> -         */
>>>> -        assert((mem_array_size + offset) < (T32_BASE - T19_BASE));
>>>> +    /*
>>>> +     * make sure 16 bit handle numbers in the headers of tables 19
>>>> +     * and 32 do not overlap.
>>>> +     */
>>>> +    assert((mem_array_size + offset) < (T32_BASE - T19_BASE));
>>>> 
>>>> -        smbios_build_type_32_table();
>>>> -        smbios_build_type_38_table();
>>>> -        smbios_build_type_41_table(errp);
>>>> -        smbios_build_type_127_table();
>>>> +    smbios_build_type_32_table();
>>>> +    smbios_build_type_38_table();
>>>> +    smbios_build_type_41_table(errp);
>>>> +    smbios_build_type_127_table();
>>>> 
>>>> -        smbios_validate_table(ms->smp.sockets);
>>>> -        smbios_entry_point_setup();
>>>> -        smbios_immutable = true;
>>>> -    }
>>>> +    smbios_validate_table(ms->smp.sockets);
>>>> +    smbios_entry_point_setup();
>>>> 
>>>>    /* return tables blob and entry point (anchor), and their sizes */
>>>>    *tables = smbios_tables;
>>>> @@ -1254,13 +1281,10 @@ void smbios_entry_add(QemuOpts *opts, Error **errp)
>>>> {
>>>>    const char *val;
>>>> 
>>>> -    assert(!smbios_immutable);
>>>> -
>>>>    val = qemu_opt_get(opts, "file");
>>>>    if (val) {
>>>>        struct smbios_structure_header *header;
>>>> -        int size;
>>>> -        struct smbios_table *table; /* legacy mode only */
>>>> +        size_t size;
>>>> 
>>>>        if (!qemu_opts_validate(opts, qemu_smbios_file_opts, errp)) {
>>>>            return;
>>>> @@ -1277,9 +1301,9 @@ void smbios_entry_add(QemuOpts *opts, Error **errp)
>>>>         * (except in legacy mode, where the second '\0' is implicit and
>>>>         *  will be inserted by the BIOS).
>>>>         */
>>>> -        smbios_tables = g_realloc(smbios_tables, smbios_tables_len + 
>>>> size);
>>>> -        header = (struct smbios_structure_header *)(smbios_tables +
>>>> -                                                    smbios_tables_len);
>>>> +        usr_blobs = g_realloc(usr_blobs, usr_blobs_len + size);
>>>> +        header = (struct smbios_structure_header *)(usr_blobs +
>>>> +                                                    usr_blobs_len);
>>>> 
>>>>        if (load_image_size(val, (uint8_t *)header, size) != size) {
>>>>            error_setg(errp, "Failed to load SMBIOS file %s", val);
>>>> @@ -1300,34 +1324,15 @@ void smbios_entry_add(QemuOpts *opts, Error **errp)
>>>>            smbios_type4_count++;
>>>>        }
>>>> 
>>>> -        smbios_tables_len += size;
>>>> -        if (size > smbios_table_max) {
>>>> -            smbios_table_max = size;
>>>> +        if (!usr_blobs_sizes) {
>>>> +            usr_blobs_sizes = g_array_new(false, false, sizeof(size_t));
>>>>        }
>>>> -        smbios_table_cnt++;
>>>> -
>>>> -        /* add a copy of the newly loaded blob to legacy smbios_entries */
>>>> -        /* NOTE: This code runs before smbios_set_defaults(), so we don't
>>>> -         *       yet know which mode (legacy vs. aggregate-table) will be
>>>> -         *       required. We therefore add the binary blob to both legacy
>>>> -         *       (smbios_entries) and aggregate (smbios_tables) tables, 
>>>> and
>>>> -         *       delete the one we don't need from smbios_set_defaults(),
>>>> -         *       once we know which machine version has been requested.
>>>> -         */
>>>> -        if (!smbios_entries) {
>>>> -            smbios_entries_len = sizeof(uint16_t);
>>>> -            smbios_entries = g_malloc0(smbios_entries_len);
>>>> +        g_array_append_val(usr_blobs_sizes, size);
>>>> +        usr_blobs_len += size;
>>>> +        if (size > usr_table_max) {
>>>> +            usr_table_max = size;
>>>>        }
>>>> -        smbios_entries = g_realloc(smbios_entries, smbios_entries_len +
>>>> -                                                   size + sizeof(*table));
>>>> -        table = (struct smbios_table *)(smbios_entries + 
>>>> smbios_entries_len);
>>>> -        table->header.type = SMBIOS_TABLE_ENTRY;
>>>> -        table->header.length = cpu_to_le16(sizeof(*table) + size);
>>>> -        memcpy(table->data, header, size);
>>>> -        smbios_entries_len += sizeof(*table) + size;
>>>> -        (*(uint16_t *)smbios_entries) =
>>>> -                cpu_to_le16(le16_to_cpu(*(uint16_t *)smbios_entries) + 1);
>>>> -        /* end: add a copy of the newly loaded blob to legacy 
>>>> smbios_entries */
>>>> +        usr_table_cnt++;
>>>> 
>>>>        return;
>>>>    }
>>>> --
>>>> 2.39.3