From: Ben Hutchings Date: Sun, 17 Aug 2025 16:06:28 +0200 Subject: bootconfig: Fix negative seeks on 32-bit with LFS enabled Forwarded: https://lore.kernel.org/linux-trace-kernel/aKHlevxeg6Y7UQrz@decadent.org.uk/T/ Commit 26dda5769509 "tools/bootconfig: Cleanup bootconfig footer size calculations" replaced some expressions of type int with the BOOTCONFIG_FOOTER_SIZE macro, which expands to an expression of type size_t, which is unsigned. On 32-bit architectures with LFS enabled (i.e. off_t is 64-bit), the seek offset of -BOOTCONFIG_FOOTER_SIZE now turns into a positive value. Fix this by casting the size to off_t before negating it. Just in case someone changes BOOTCONFIG_MAGIC_LEN to have type size_t later, do the same thing to the seek offset of -BOOTCONFIG_MAGIC_LEN. Fixes: 26dda5769509 ("tools/bootconfig: Cleanup bootconfig footer size calculations") Signed-off-by: Ben Hutchings --- tools/bootconfig/main.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/tools/bootconfig/main.c +++ b/tools/bootconfig/main.c @@ -193,7 +193,7 @@ static int load_xbc_from_initrd(int fd, if (stat.st_size < BOOTCONFIG_FOOTER_SIZE) return 0; - if (lseek(fd, -BOOTCONFIG_MAGIC_LEN, SEEK_END) < 0) + if (lseek(fd, -(off_t)BOOTCONFIG_MAGIC_LEN, SEEK_END) < 0) return pr_errno("Failed to lseek for magic", -errno); if (read(fd, magic, BOOTCONFIG_MAGIC_LEN) < 0) @@ -203,7 +203,7 @@ static int load_xbc_from_initrd(int fd, if (memcmp(magic, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN) != 0) return 0; - if (lseek(fd, -BOOTCONFIG_FOOTER_SIZE, SEEK_END) < 0) + if (lseek(fd, -(off_t)BOOTCONFIG_FOOTER_SIZE, SEEK_END) < 0) return pr_errno("Failed to lseek for size", -errno); if (read(fd, &size, sizeof(uint32_t)) < 0)