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462d0b066b
Sashiko reported that on 32-bit systems, if an attacker crafts size in
the bootconfig footer such that adding BOOTCONFIG_FOOTER_SIZE wraps around
(for instance, if size is 0xFFFFFFFF), the size check in
load_xbc_from_initrd() can be bypassed:
if (stat.st_size < size + BOOTCONFIG_FOOTER_SIZE) {
pr_err("bootconfig size is too big\n");
return -E2BIG;
}
Furthermore, on 64-bit systems with an initrd > 4.29 GB, comparing a
corrupted 32-bit size (e.g. 0xFFFFFFFF) against
stat.st_size - BOOTCONFIG_FOOTER_SIZE can also bypass the check if
size is not bounded. Similarly, load_xbc_file() passes 64-bit stat.st_size
directly into the 32-bit int size parameter of load_xbc_fd(), truncating
large standalone files (>= 2GB).
In both cases, passing 0xFFFFFFFF to load_xbc_fd() truncates to -1,
resulting in malloc(0), an integer overflow in read(), and an
out-of-bounds null-byte write.
Fix this by:
1. Rejecting size > XBC_DATA_MAX or
size > stat.st_size - BOOTCONFIG_FOOTER_SIZE in load_xbc_from_initrd().
2. Rejecting stat.st_size > XBC_DATA_MAX in load_xbc_file() before passing
it to load_xbc_fd().
3. Checking size < 0 || size > XBC_DATA_MAX defensively in load_xbc_fd().
Link: https://lore.kernel.org/all/178905332413.213925.3179977110281463499.stgit@devnote2/
Fixes:
|
||
|---|---|---|
| .. | ||
| include/linux | ||
| samples | ||
| scripts | ||
| .gitignore | ||
| main.c | ||
| Makefile | ||
| test-bootconfig.sh | ||