From: Masami Hiramatsu (Google) <[email protected]> If a bootconfig buffer contains an intermediate null character in the middle of the configuration, xbc_parse_tree() stops at the null character because string delimiter searches (e.g. strpbrk()) stop at '\0', and cleanly breaks out of the loop without error. As a result, any configuration data following the intermediate null character is silently ignored, allowing unparsed or potentially malicious data to be hidden after an early termination.
Fix this in xbc_parse_tree() by checking that no non-null data remains between the parser termination point and the end of the input buffer. Trailing null characters (such as alignment padding in initrd) continue to be accepted as valid. Also update apply_xbc() in tools/bootconfig/main.c to calculate the buffer size based on the loaded file size rather than strlen(), so that files with intermediate null characters are not truncated before validation. Assisted-by: Antigravity:gemini-3.8-flash Signed-off-by: Masami Hiramatsu (Google) <[email protected]> Reviewed-by: Sang-Heon Jeon <[email protected]> --- lib/bootconfig.c | 7 +++++++ tools/bootconfig/main.c | 4 +++- tools/bootconfig/test-bootconfig.sh | 12 ++++++++++++ 3 files changed, 22 insertions(+), 1 deletion(-) diff --git a/lib/bootconfig.c b/lib/bootconfig.c index 89c88e359179..61cae6d6e3f8 100644 --- a/lib/bootconfig.c +++ b/lib/bootconfig.c @@ -1119,6 +1119,13 @@ static int __init xbc_parse_tree(void) } } while (!ret); + if (!ret) { + while (p < xbc_data + xbc_data_size - 1 && *p == '\0') + p++; + if (p < xbc_data + xbc_data_size - 1) + ret = xbc_parse_error("Unexpected data after null character", p); + } + return ret; } diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c index 17d971d47f87..aff169ba75b8 100644 --- a/tools/bootconfig/main.c +++ b/tools/bootconfig/main.c @@ -433,7 +433,9 @@ static int apply_xbc(const char *path, const char *xbc_path) pr_err("Failed to load %s : %d\n", xbc_path, ret); return ret; } - size = strlen(buf) + 1; + size = ret; + if (size == 0 || buf[size - 1] != '\0') + size++; csum = xbc_calc_checksum(buf, size); /* Backup the bootconfig data */ diff --git a/tools/bootconfig/test-bootconfig.sh b/tools/bootconfig/test-bootconfig.sh index fc69f815ce4a..530ce7e28d63 100755 --- a/tools/bootconfig/test-bootconfig.sh +++ b/tools/bootconfig/test-bootconfig.sh @@ -180,6 +180,18 @@ EOF $BOOTCONF -a $TEMPCONF $INITRD 2> $OUTFILE xpass grep -q "1:1" $OUTFILE +echo "Intermediate null character test" +printf "key = value\n\0extra = data\n" > $TEMPCONF +xfail $BOOTCONF -a $TEMPCONF $INITRD +$BOOTCONF -a $TEMPCONF $INITRD 2> $OUTFILE +xpass grep -q "Unexpected" $OUTFILE + +echo "Trailing null character test" +printf "key = value\n\0" > $TEMPCONF +xpass $BOOTCONF -a $TEMPCONF $INITRD +$BOOTCONF $INITRD > $OUTFILE +xpass grep -q "value" $OUTFILE + echo "=== expected failure cases ===" for i in samples/bad-* ; do xfail $BOOTCONF -a $i $INITRD
