github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-06 21:58:01 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

bootconfig: Reject unexpected data after null character

Browse Source 
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.

Link: https://lore.kernel.org/all/178913598628.248794.1048773774471250986.stgit@devnote2/

Assisted-by: LLM
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Sang-Heon Jeon <ekffu200098@gmail.com>
This commit is contained in:
Masami Hiramatsu (Google) 2026-09-11 23:13:06 +09:00
parent 958c01049e
commit fac634087a
3 changed files with 22 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
lib/bootconfig.c
View File

@ -1121,6 +1121,13 @@ 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;
}

4
tools/bootconfig/main.c
View File

@ -431,7 +431,9 @@ 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 */

12
tools/bootconfig/test-bootconfig.sh
View File

@ -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