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initramfs: Check negative timestamp to prevent broken cpio archive

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Similar to commit 4c9d410f32 ("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>
This commit is contained in:
Benjamin Gray 2023-03-20 15:08:38 +11:00 committed by Masahiro Yamada
parent aa7d233f45
commit 5efb685bb3
1 changed files with 9 additions and 3 deletions
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12
usr/gen_init_cpio.c
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@ -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);
}