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authorJacob Garber <jgarber1@ualberta.ca>2019-06-26 16:18:16 -0600
committerPatrick Georgi <pgeorgi@google.com>2019-08-20 15:27:42 +0000
commit9172b6920cac2c4dabf19e529dbfed91b15685c5 (patch)
tree761b138ce45fface88f8babba31d48bff43203d5 /src/arch
parent5fa756cc97de1ed30ac3fd4d5ddb85f079efe521 (diff)
downloadcoreboot-9172b6920cac2c4dabf19e529dbfed91b15685c5.tar.xz
src: Remove variable length arrays
Variable length arrays were a feature added in C99 that allows the length of an array to be determined at runtime. Eg. int sum(size_t n) { int arr[n]; ... } This adds a small amount of runtime overhead, but is also very dangerous, since it allows use of an unlimited amount of stack memory, potentially leading to stack overflow. This is only worsened in coreboot, which often has very little stack space to begin with. Citing concerns like this, all instances of VLA's were recently removed from the Linux kernel. In the immortal words of Linus Torvalds [0], AND USING VLA'S IS ACTIVELY STUPID! It generates much more code, and much _slower_ code (and more fragile code), than just using a fixed key size would have done. [...] Anyway, some of these are definitely easy to just fix, and using VLA's is actively bad not just for security worries, but simply because VLA's are a really horribly bad idea in general in the kernel. This patch follows suit and zaps all VLA's in coreboot. Some of the existing VLA's are accidental ones, and all but one can be replaced with small fixed-size buffers. The single tricky exception is in the SPI controller interface, which will require a rewrite of old drivers to remove [1]. [0] https://lkml.org/lkml/2018/3/7/621 [1] https://ticket.coreboot.org/issues/217 Change-Id: I7d9d1ddadbf1cee5f695165bbe3f0effb7bd32b9 Signed-off-by: Jacob Garber <jgarber1@ualberta.ca> Reviewed-on: https://review.coreboot.org/c/coreboot/+/33821 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Diffstat (limited to 'src/arch')
-rw-r--r--src/arch/x86/smbios.c13
1 files changed, 5 insertions, 8 deletions
diff --git a/src/arch/x86/smbios.c b/src/arch/x86/smbios.c
index 346e874217..f95516eee6 100644
--- a/src/arch/x86/smbios.c
+++ b/src/arch/x86/smbios.c
@@ -275,20 +275,18 @@ static void trim_trailing_whitespace(char *buffer, size_t buffer_size)
static void smbios_fill_dimm_part_number(const char *part_number,
struct smbios_type17 *t)
{
- const size_t trimmed_buffer_size = DIMM_INFO_PART_NUMBER_SIZE;
-
int invalid;
size_t i, len;
- char trimmed_part_number[trimmed_buffer_size];
+ char trimmed_part_number[DIMM_INFO_PART_NUMBER_SIZE];
- strncpy(trimmed_part_number, part_number, trimmed_buffer_size);
- trimmed_part_number[trimmed_buffer_size - 1] = '\0';
+ strncpy(trimmed_part_number, part_number, sizeof(trimmed_part_number));
+ trimmed_part_number[sizeof(trimmed_part_number) - 1] = '\0';
/*
* SPD mandates that unused characters be represented with a ' '.
* We don't want to publish the whitespace in the SMBIOS tables.
*/
- trim_trailing_whitespace(trimmed_part_number, trimmed_buffer_size);
+ trim_trailing_whitespace(trimmed_part_number, sizeof(trimmed_part_number));
len = strlen(trimmed_part_number);
@@ -304,8 +302,7 @@ static void smbios_fill_dimm_part_number(const char *part_number,
/* Null String in Part Number will have "None" instead. */
t->part_number = smbios_add_string(t->eos, "None");
} else if (invalid) {
- char string_buffer[trimmed_buffer_size +
- 10 /* strlen("Invalid ()") */];
+ char string_buffer[sizeof(trimmed_part_number) + 10];
snprintf(string_buffer, sizeof(string_buffer), "Invalid (%s)",
trimmed_part_number);