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From 7425d421340594f50c717ff7129b6ee71280a447 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20=C5=A0tetiar?= <ynezz@true.cz>
Date: Mon, 9 Dec 2019 15:27:16 +0100
Subject: blob: fix OOB access in blob_check_type
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Found by fuzzer:
ERROR: AddressSanitizer: SEGV on unknown address 0x602100000455
The signal is caused by a READ memory access.
#0 in blob_check_type blob.c:214:43
#1 in blob_parse_attr blob.c:234:9
#2 in blob_parse_untrusted blob.c:272:12
#3 in fuzz_blob_parse tests/fuzzer/test-blob-parse-fuzzer.c:34:2
#4 in LLVMFuzzerTestOneInput tests/fuzzer/test-blob-parse-fuzzer.c:39:2
Caused by following line:
if (type == BLOB_ATTR_STRING && data[len - 1] != 0)
where len was pointing outside of the data buffer.
Signed-off-by: Petr Štetiar <ynezz@true.cz>
---
blob.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
--- a/blob.c
+++ b/blob.c
@@ -218,20 +218,33 @@ blob_check_type(const void *ptr, unsigne
}
static int
-blob_parse_attr(struct blob_attr *attr, struct blob_attr **data, const struct blob_attr_info *info, int max)
+blob_parse_attr(struct blob_attr *attr, size_t attr_len, struct blob_attr **data, const struct blob_attr_info *info, int max)
{
+ int id;
+ size_t len;
int found = 0;
- int id = blob_id(attr);
- size_t len = blob_len(attr);
+ size_t data_len;
+ if (!attr || attr_len < sizeof(struct blob_attr))
+ return 0;
+
+ id = blob_id(attr);
if (id >= max)
return 0;
+ len = blob_raw_len(attr);
+ if (len > attr_len || len < sizeof(struct blob_attr))
+ return 0;
+
+ data_len = blob_len(attr);
+ if (data_len > len)
+ return 0;
+
if (info) {
int type = info[id].type;
if (type < BLOB_ATTR_LAST) {
- if (!blob_check_type(blob_data(attr), len, type))
+ if (!blob_check_type(blob_data(attr), data_len, type))
return 0;
}
@@ -285,7 +298,7 @@ blob_parse(struct blob_attr *attr, struc
memset(data, 0, sizeof(struct blob_attr *) * max);
blob_for_each_attr(pos, attr, rem) {
- found += blob_parse_attr(pos, data, info, max);
+ found += blob_parse_attr(pos, rem, data, info, max);
}
return found;
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