[PATCH RFC 1/7] Revert "x86: don't let decompressed kernel image clobber setup_data"

Michael S. Tsirkin
2023-02-08T21:13:30Z

This reverts commit eac7a7791bb6d719233deed750034042318ffd56.

Fixes: eac7a7791b ("x86: don't let decompressed kernel image clobber setup_data")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
include/hw/i386/microvm.h | 5 ++--
include/hw/nvram/fw_cfg.h | 9 -------
hw/i386/microvm.c | 15 ++++-------
hw/i386/x86.c | 52 ++++++++++++++++++---------------------
hw/nvram/fw_cfg.c | 9 -------
5 files changed, 31 insertions(+), 59 deletions(-)

diff --git a/include/hw/i386/microvm.h b/include/hw/i386/microvm.h
index e8af61f194..fad97a891d 100644
--- a/include/hw/i386/microvm.h
+++ b/include/hw/i386/microvm.h
@@ -50,9 +50,8 @@
*/

/* Platform virtio definitions */
-#define VIRTIO_MMIO_BASE 0xfeb00000
-#define VIRTIO_CMDLINE_MAXLEN 64
-#define VIRTIO_CMDLINE_TOTAL_MAX_LEN ((VIRTIO_CMDLINE_MAXLEN + 1) * 16)
+#define VIRTIO_MMIO_BASE 0xfeb00000
+#define VIRTIO_CMDLINE_MAXLEN 64

#define GED_MMIO_BASE 0xfea00000
#define GED_MMIO_BASE_MEMHP (GED_MMIO_BASE + 0x100)
diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
index 990dcdbb2e..2e503904dc 100644
--- a/include/hw/nvram/fw_cfg.h
+++ b/include/hw/nvram/fw_cfg.h
@@ -139,15 +139,6 @@ void fw_cfg_add_bytes_callback(FWCfgState *s, uint16_t key,
void *data, size_t len,
bool read_only);

-/**
- * fw_cfg_read_bytes_ptr:
- * @s: fw_cfg device being modified
- * @key: selector key value for new fw_cfg item
- *
- * Reads an existing fw_cfg data pointer.
- */
-void *fw_cfg_read_bytes_ptr(FWCfgState *s, uint16_t key);
-
/**
* fw_cfg_add_string:
* @s: fw_cfg device being modified
diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
index 29f30dd6d3..170a331e3f 100644
--- a/hw/i386/microvm.c
+++ b/hw/i386/microvm.c
@@ -378,8 +378,7 @@ static void microvm_fix_kernel_cmdline(MachineState *machine)
MicrovmMachineState *mms = MICROVM_MACHINE(machine);
BusState *bus;
BusChild *kid;
- char *cmdline, *existing_cmdline;
- size_t len;
+ char *cmdline;

/*
* Find MMIO transports with attached devices, and add them to the kernel
@@ -388,8 +387,7 @@ static void microvm_fix_kernel_cmdline(MachineState *machine)
* Yes, this is a hack, but one that heavily improves the UX without
* introducing any significant issues.
*/
- existing_cmdline = fw_cfg_read_bytes_ptr(x86ms->fw_cfg, FW_CFG_CMDLINE_DATA);
- cmdline = g_strdup(existing_cmdline);
+ cmdline = g_strdup(machine->kernel_cmdline);
bus = sysbus_get_default();
QTAILQ_FOREACH(kid, &bus->children, sibling) {
DeviceState *dev = kid->child;
@@ -413,12 +411,9 @@ static void microvm_fix_kernel_cmdline(MachineState *machine)
}
}

- len = strlen(cmdline);
- if (len > VIRTIO_CMDLINE_TOTAL_MAX_LEN + strlen(existing_cmdline)) {
- fprintf(stderr, "qemu: virtio mmio cmdline too large, skipping\n");
- } else {
- memcpy(existing_cmdline, cmdline, len + 1);
- }
+ fw_cfg_modify_i32(x86ms->fw_cfg, FW_CFG_CMDLINE_SIZE, strlen(cmdline) + 1);
+ fw_cfg_modify_string(x86ms->fw_cfg, FW_CFG_CMDLINE_DATA, cmdline);
+
g_free(cmdline);
}

diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index eaff4227bd..78cc131926 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -50,7 +50,6 @@
#include "hw/intc/i8259.h"
#include "hw/rtc/mc146818rtc.h"
#include "target/i386/sev.h"
-#include "hw/i386/microvm.h"

#include "hw/acpi/cpu_hotplug.h"
#include "hw/irq.h"
@@ -814,18 +813,12 @@ void x86_load_linux(X86MachineState *x86ms,
const char *kernel_filename = machine->kernel_filename;
const char *initrd_filename = machine->initrd_filename;
const char *dtb_filename = machine->dtb;
- char *kernel_cmdline;
+ const char *kernel_cmdline = machine->kernel_cmdline;
SevKernelLoaderContext sev_load_ctx = {};
enum { RNG_SEED_LENGTH = 32 };

- /*
- * Add the NUL terminator, some padding for the microvm cmdline fiddling
- * hack, and then align to 16 bytes as a paranoia measure
- */
- cmdline_size = (strlen(machine->kernel_cmdline) + 1 +
- VIRTIO_CMDLINE_TOTAL_MAX_LEN + 16) & ~15;
- /* Make a copy, since we might append arbitrary bytes to it later. */
- kernel_cmdline = g_strndup(machine->kernel_cmdline, cmdline_size);
+ /* Align to 16 bytes as a paranoia measure */
+ cmdline_size = (strlen(kernel_cmdline) + 16) & ~15;

/* load the kernel header */
f = fopen(kernel_filename, "rb");
@@ -966,6 +959,12 @@ void x86_load_linux(X86MachineState *x86ms,
initrd_max = x86ms->below_4g_mem_size - acpi_data_size - 1;
}

+ fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_ADDR, cmdline_addr);
+ fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_SIZE, strlen(kernel_cmdline) + 1);
+ fw_cfg_add_string(fw_cfg, FW_CFG_CMDLINE_DATA, kernel_cmdline);
+ sev_load_ctx.cmdline_data = (char *)kernel_cmdline;
+ sev_load_ctx.cmdline_size = strlen(kernel_cmdline) + 1;
+
if (protocol >= 0x202) {
stl_p(header + 0x228, cmdline_addr);
} else {
@@ -1092,24 +1091,27 @@ void x86_load_linux(X86MachineState *x86ms,
exit(1);
}

- setup_data_offset = cmdline_size;
- cmdline_size += sizeof(SetupData) + dtb_size;
- kernel_cmdline = g_realloc(kernel_cmdline, cmdline_size);
- setup_data = (void *)kernel_cmdline + setup_data_offset;
+ setup_data_offset = QEMU_ALIGN_UP(kernel_size, 16);
+ kernel_size = setup_data_offset + sizeof(SetupData) + dtb_size;
+ kernel = g_realloc(kernel, kernel_size);
+
+
+ setup_data = (SetupData *)(kernel + setup_data_offset);
setup_data->next = cpu_to_le64(first_setup_data);
- first_setup_data = cmdline_addr + setup_data_offset;
+ first_setup_data = prot_addr + setup_data_offset;
setup_data->type = cpu_to_le32(SETUP_DTB);
setup_data->len = cpu_to_le32(dtb_size);
+
load_image_size(dtb_filename, setup_data->data, dtb_size);
}

- if (!legacy_no_rng_seed && protocol >= 0x209) {
- setup_data_offset = cmdline_size;
- cmdline_size += sizeof(SetupData) + RNG_SEED_LENGTH;
- kernel_cmdline = g_realloc(kernel_cmdline, cmdline_size);
- setup_data = (void *)kernel_cmdline + setup_data_offset;
+ if (!legacy_no_rng_seed) {
+ setup_data_offset = QEMU_ALIGN_UP(kernel_size, 16);
+ kernel_size = setup_data_offset + sizeof(SetupData) + RNG_SEED_LENGTH;
+ kernel = g_realloc(kernel, kernel_size);
+ setup_data = (SetupData *)(kernel + setup_data_offset);
setup_data->next = cpu_to_le64(first_setup_data);
- first_setup_data = cmdline_addr + setup_data_offset;
+ first_setup_data = prot_addr + setup_data_offset;
setup_data->type = cpu_to_le32(SETUP_RNG_SEED);
setup_data->len = cpu_to_le32(RNG_SEED_LENGTH);
qemu_guest_getrandom_nofail(setup_data->data, RNG_SEED_LENGTH);
@@ -1120,12 +1122,6 @@ void x86_load_linux(X86MachineState *x86ms,
fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, kernel, kernel_size);
}

- fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_ADDR, cmdline_addr);
- fw_cfg_add_i32(fw_cfg, FW_CFG_CMDLINE_SIZE, cmdline_size);
- fw_cfg_add_bytes(fw_cfg, FW_CFG_CMDLINE_DATA, kernel_cmdline, cmdline_size);
- sev_load_ctx.cmdline_data = (char *)kernel_cmdline;
- sev_load_ctx.cmdline_size = cmdline_size;
-
fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, prot_addr);
fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, kernel_size);
sev_load_ctx.kernel_data = (char *)kernel;
@@ -1138,7 +1134,7 @@ void x86_load_linux(X86MachineState *x86ms,
* kernel on the other side of the fw_cfg interface matches the hash of the
* file the user passed in.
*/
- if (!sev_enabled() && first_setup_data) {
+ if (!sev_enabled()) {
SetupDataFixup *fixup = g_malloc(sizeof(*fixup));

memcpy(setup, header, MIN(sizeof(header), setup_size));
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 432754eda4..a00881bc64 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -741,15 +741,6 @@ void fw_cfg_add_bytes(FWCfgState *s, uint16_t key, void *data, size_t len)
fw_cfg_add_bytes_callback(s, key, NULL, NULL, NULL, data, len, true);
}

-void *fw_cfg_read_bytes_ptr(FWCfgState *s, uint16_t key)
-{
- int arch = !!(key & FW_CFG_ARCH_LOCAL);
-
- key &= FW_CFG_ENTRY_MASK;
- assert(key < fw_cfg_max_entry(s));
- return s->entries[arch][key].data;
-}
-
void fw_cfg_add_string(FWCfgState *s, uint16_t key, const char *value)
{
size_t sz = strlen(value) + 1;
--
MST