bootconfig: reject unexpected data after null character

Patch series "bootconfig: Reject unexpected data after null character and
cleanups", v2.

Make bootconfig reject unexpected config data after null character and
implement other cleanups including tools/bootconfig to consolidate
bootconfig initialization with errors, and to skip internal tree sanity
checks in kernel.


This patch (of 4):

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
Link: https://lore.kernel.org/178913597653.248794.1237187523153227751.stgit@devnote2
Link: https://lore.kernel.org/178913598628.248794.1048773774471250986.stgit@devnote2
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Sang-Heon Jeon <ekffu200098@gmail.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/bootconfig.c b/lib/bootconfig.c
index f248b5770291..b6adf8b27474 100644
--- a/lib/bootconfig.c
+++ b/lib/bootconfig.c
@@ -1118,6 +1118,13 @@ 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;
 }