Commit 5efb685b authored Mar 20, 2023 by Benjamin Gray Committed by Masahiro Yamada Apr 16, 2023

initramfs: Check negative timestamp to prevent broken cpio archive



Similar to commit 4c9d410f ("initramfs: Check timestamp to prevent
broken cpio archive"), except asserts that the timestamp is
non-negative. This can happen when the KBUILD_BUILD_TIMESTAMP is a value
before UNIX epoch, which may be set when making reproducible builds that
don't want to look like they use a valid date.

While support for dates before 1970 might not be supported, this is more
about preventing undetected CPIO corruption. The printf's use a minimum
length format specifier, and will happily make the field longer than 8
characters if they need to.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Tested-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

parent aa7d233f

usr/gen_init_cpio.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -353,6 +353,12 @@ static int cpio_mkfile(const char name, const char location,
		buf.st_mtime = 0xffffffff;
		}

		if (buf.st_mtime < 0) {
		fprintf(stderr, "%s: Timestamp negative, clipping.\n",
		location);
		buf.st_mtime = 0;
		}

		if (buf.st_size > 0xffffffff) {
		fprintf(stderr, "%s: Size exceeds maximum cpio file size\n",
		location);
		@@ -602,10 +608,10 @@ int main (int argc, char *argv[])
		/*
		* Timestamps after 2106-02-07 06:28:15 UTC have an ascii hex time_t
		* representation that exceeds 8 chars and breaks the cpio header
		* specification.
		* specification. Negative timestamps similarly exceed 8 chars.
		*/
		if (default_mtime > 0xffffffff) {
		fprintf(stderr, "ERROR: Timestamp too large for cpio format\n");
		if (default_mtime > 0xffffffff \|\| default_mtime < 0) {
		fprintf(stderr, "ERROR: Timestamp out of range for cpio format\n");
		exit(1);
		}