Similar to commit 4c9d410f32b3 ("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.
Unified · Split
| @@ -353,6 +353,12 @@ static int cpio_mkfile(const char *name, const char *location, · 352 unmodified lines | ||
| 353 | 353 | buf.st_mtime = 0xffffffff; |
| 354 | 354 | } |
| 355 | 355 | |
| 356 | + if (buf.st_mtime < 0) { | |
| 357 | + fprintf(stderr, "%s: Timestamp negative, clipping.\n", | |
| 358 | + location); | |
| 359 | + buf.st_mtime = 0; | |
| 360 | + } | |
| 361 | + | |
| 356 | 362 | if (buf.st_size > 0xffffffff) { |
| 357 | 363 | fprintf(stderr, "%s: Size exceeds maximum cpio file size\n", |
| 358 | 364 | location); |
| @@ -602,10 +608,10 @@ int main (int argc, char *argv[]) · 243 unmodified lines | ||
| 602 | 608 | /* |
| 603 | 609 | * Timestamps after 2106-02-07 06:28:15 UTC have an ascii hex time_t |
| 604 | 610 | * representation that exceeds 8 chars and breaks the cpio header |
| 605 | − * specification. | |
| 611 | + * specification. Negative timestamps similarly exceed 8 chars. | |
| 606 | 612 | */ |
| 607 | − if (default_mtime > 0xffffffff) { | |
| 608 | − fprintf(stderr, "ERROR: Timestamp too large for cpio format\n"); | |
| 613 | + if (default_mtime > 0xffffffff || default_mtime < 0) { | |
| 614 | + fprintf(stderr, "ERROR: Timestamp out of range for cpio format\n"); | |
| 609 | 615 | exit(1); |
| 610 | 616 | } |
| 611 | 617 | |