From 6ed5e20466c79e3b3350bae39f678f73cf564b4e Mon Sep 17 00:00:00 2001 From: Ben Hutchings Date: Wed, 23 Jul 2025 12:49:25 +0200 Subject: [PATCH] bootconfig: Fix unaligned access when building footer Currently we add padding between the bootconfig text and footer to ensure that the footer is aligned within the initramfs image. However, because only the bootconfig data is held in memory, not the full initramfs image, the footer may not be naturally aligned in memory. This can result in an alignment fault (SIGBUS) when writing the footer on some architectures, such as sparc. Build the footer in a struct on the stack before adding it to the buffer. References: https://buildd.debian.org/status/fetch.php?pkg=linux&arch=sparc64&ver=6.16%7Erc7-1%7Eexp1&stamp=1753209801&raw=0 Link: https://lore.kernel.org/all/aIC-NTw-cdm9ZGFw@decadent.org.uk/ Signed-off-by: Ben Hutchings Signed-off-by: Masami Hiramatsu (Google) --- tools/bootconfig/main.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-) diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c index 4988e23a1422..57c669d2aa90 100644 --- a/tools/bootconfig/main.c +++ b/tools/bootconfig/main.c @@ -11,6 +11,7 @@ #include #include #include +#include #include @@ -363,7 +364,12 @@ static int delete_xbc(const char *path) static int apply_xbc(const char *path, const char *xbc_path) { - char *buf, *data, *p; + struct { + uint32_t size; + uint32_t csum; + char magic[BOOTCONFIG_MAGIC_LEN]; + } footer; + char *buf, *data; size_t total_size; struct stat stat; const char *msg; @@ -433,17 +439,13 @@ static int apply_xbc(const char *path, const char *xbc_path) size += pad; /* Add a footer */ - p = data + size; - *(uint32_t *)p = htole32(size); - p += sizeof(uint32_t); + footer.size = htole32(size); + footer.csum = htole32(csum); + memcpy(footer.magic, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN); + static_assert(sizeof(footer) == BOOTCONFIG_FOOTER_SIZE); + memcpy(data + size, &footer, BOOTCONFIG_FOOTER_SIZE); - *(uint32_t *)p = htole32(csum); - p += sizeof(uint32_t); - - memcpy(p, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN); - p += BOOTCONFIG_MAGIC_LEN; - - total_size = p - data; + total_size = size + BOOTCONFIG_FOOTER_SIZE; ret = write(fd, data, total_size); if (ret < total_size) { -- 2.47.2