bootconfig: Fix negative seeks on 32-bit with LFS enabled

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.

Link: https://lore.kernel.org/all/aKHlevxeg6Y7UQrz@decadent.org.uk/
Fixes: 26dda5769509 ("tools/bootconfig: Cleanup bootconfig footer size calculations")
Signed-off-by: Ben Hutchings <benh@debian.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c
index 57c669d2aa90f5a40e548c4724d2c6ebe2e28f3e..55d59ed507d541e54cf2c481246326b959dd7208 100644 (file)
--- a/tools/bootconfig/main.c
+++ b/tools/bootconfig/main.c
@@ -193,7 +193,7 @@ static int load_xbc_from_initrd(int fd, char **buf)
        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, char **buf)
        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)