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x86/microcode/intel: Refactor Intel microcode blob loading

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Change generic_load_microcode() to use the iov_iter API instead of a
clumsy open-coded version which has to pay attention to __user data
or kernel data, depending on the loading method. This allows to avoid
explicit casting between user and kernel pointers.

Because the iov_iter API makes it hard to read the same location twice,
as a side effect, also fix a double-read of the microcode header (which
could e.g. lead to out-of-bounds reads in microcode_sanity_check()).

Not that it matters much, only root is allowed to load microcode
anyway...

 [ bp: Massage a bit, sort function-local variables. ]

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190404111128.131157-1-jannh@google.com
This commit is contained in:
Jann Horn 2019-04-04 13:11:28 +02:00 committed by Borislav Petkov
parent 79a3aaa7b8
commit 7e94a7b659
1 changed files with 36 additions and 35 deletions
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71
arch/x86/kernel/cpu/microcode/intel.c
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@ -31,6 +31,7 @@
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/cpu.h>
#include <linux/uio.h>
#include <linux/mm.h>
#include <asm/microcode_intel.h>
@ -861,32 +862,33 @@ static enum ucode_state apply_microcode_intel(int cpu)
return ret;
}
static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
int (*get_ucode_data)(void *, const void *, size_t))
static enum ucode_state generic_load_microcode(int cpu, struct iov_iter *iter)
{
struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
u8 *ucode_ptr = data, *new_mc = NULL, *mc = NULL;
int new_rev = uci->cpu_sig.rev;
unsigned int leftover = size;
unsigned int curr_mc_size = 0, new_mc_size = 0;
unsigned int csig, cpf;
enum ucode_state ret = UCODE_OK;
int new_rev = uci->cpu_sig.rev;
u8 *new_mc = NULL, *mc = NULL;
unsigned int csig, cpf;
while (leftover) {
while (iov_iter_count(iter)) {
struct microcode_header_intel mc_header;
unsigned int mc_size;
unsigned int mc_size, data_size;
u8 *data;
if (leftover < sizeof(mc_header)) {
pr_err("error! Truncated header in microcode data file\n");
if (!copy_from_iter_full(&mc_header, sizeof(mc_header), iter)) {
pr_err("error! Truncated or inaccessible header in microcode data file\n");
break;
}
if (get_ucode_data(&mc_header, ucode_ptr, sizeof(mc_header)))
break;
mc_size = get_totalsize(&mc_header);
if (!mc_size || mc_size > leftover) {
pr_err("error! Bad data in microcode data file\n");
if (mc_size < sizeof(mc_header)) {
pr_err("error! Bad data in microcode data file (totalsize too small)\n");
break;
}
data_size = mc_size - sizeof(mc_header);
if (data_size > iov_iter_count(iter)) {
pr_err("error! Bad data in microcode data file (truncated file?)\n");
break;
}
@ -899,7 +901,9 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
curr_mc_size = mc_size;
}
if (get_ucode_data(mc, ucode_ptr, mc_size) ||
memcpy(mc, &mc_header, sizeof(mc_header));
data = mc + sizeof(mc_header);
if (!copy_from_iter_full(data, data_size, iter) ||
microcode_sanity_check(mc, 1) < 0) {
break;
}
@ -914,14 +918,11 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
mc = NULL; /* trigger new vmalloc */
ret = UCODE_NEW;
}
ucode_ptr += mc_size;
leftover -= mc_size;
}
vfree(mc);
if (leftover) {
if (iov_iter_count(iter)) {
vfree(new_mc);
return UCODE_ERROR;
}
@ -945,12 +946,6 @@ static enum ucode_state generic_load_microcode(int cpu, void *data, size_t size,
return ret;
}
static int get_ucode_fw(void *to, const void *from, size_t n)
{
memcpy(to, from, n);
return 0;
}
static bool is_blacklisted(unsigned int cpu)
{
struct cpuinfo_x86 *c = &cpu_data(cpu);
@ -977,10 +972,12 @@ static bool is_blacklisted(unsigned int cpu)
static enum ucode_state request_microcode_fw(int cpu, struct device *device,
bool refresh_fw)
{
char name[30];
struct cpuinfo_x86 *c = &cpu_data(cpu);
const struct firmware *firmware;
struct iov_iter iter;
enum ucode_state ret;
struct kvec kvec;
char name[30];
if (is_blacklisted(cpu))
return UCODE_NFOUND;
@ -993,26 +990,30 @@ static enum ucode_state request_microcode_fw(int cpu, struct device *device,
return UCODE_NFOUND;
}
ret = generic_load_microcode(cpu, (void *)firmware->data,
firmware->size, &get_ucode_fw);
kvec.iov_base = (void *)firmware->data;
kvec.iov_len = firmware->size;
iov_iter_kvec(&iter, WRITE, &kvec, 1, firmware->size);
ret = generic_load_microcode(cpu, &iter);
release_firmware(firmware);
return ret;
}
static int get_ucode_user(void *to, const void *from, size_t n)
{
return copy_from_user(to, from, n);
}
static enum ucode_state
request_microcode_user(int cpu, const void __user *buf, size_t size)
{
struct iov_iter iter;
struct iovec iov;
if (is_blacklisted(cpu))
return UCODE_NFOUND;
return generic_load_microcode(cpu, (void *)buf, size, &get_ucode_user);
iov.iov_base = (void __user *)buf;
iov.iov_len = size;
iov_iter_init(&iter, WRITE, &iov, 1, size);
return generic_load_microcode(cpu, &iter);
}
static struct microcode_ops microcode_intel_ops = {