[PATCH cgi-io 07/12] Fix off-by-one in postdecode_fields

[Petr Štetiar]

Fixes following error found by fuzzer:

 ERROR: AddressSanitizer: SEGV on unknown address 0x60c000120000 (pc 0x00000054f64f bp 0x000000000008 sp 0x7ffe4fc2c120 T0)
 The signal is caused by a READ memory access.
    #0 0x54f64f in postdecode_fields cgi-io/util.c:93:7
    #1 0x54f382 in LLVMFuzzerTestOneInput cgi-io/tests/fuzz/test-fuzz.c:36:6

That is caused by reading 1 byte past the size of the buffer.

Signed-off-by: Petr Å tetiar <ynezz at true.cz>
---
 ...crash-9adc1b00fe9189d66d3bfd8b7759b003cf3f5427 | Bin 0 -> 191 bytes
 ...crash-c1e3b9cd71f83cc0de5ab4c0e3db39316cd5c6c0 |   1 +
 util.c                                            |   2 +-
 3 files changed, 2 insertions(+), 1 deletion(-)
 create mode 100644 tests/fuzz/corpus/crash-9adc1b00fe9189d66d3bfd8b7759b003cf3f5427
 create mode 100644 tests/fuzz/corpus/crash-c1e3b9cd71f83cc0de5ab4c0e3db39316cd5c6c0

diff --git a/tests/fuzz/corpus/crash-9adc1b00fe9189d66d3bfd8b7759b003cf3f5427 b/tests/fuzz/corpus/crash-9adc1b00fe9189d66d3bfd8b7759b003cf3f5427
new file mode 100644
index 0000000000000000000000000000000000000000..7122f990552e3b5228c521d76372669707f57e5b
GIT binary patch
literal 191
YcmZQ*APQ9DR3(H{22+AMrXZUO03e258vp<R

literal 0
HcmV?d00001

diff --git a/tests/fuzz/corpus/crash-c1e3b9cd71f83cc0de5ab4c0e3db39316cd5c6c0 b/tests/fuzz/corpus/crash-c1e3b9cd71f83cc0de5ab4c0e3db39316cd5c6c0
new file mode 100644
index 000000000000..264f4b1a64f9
--- /dev/null
+++ b/tests/fuzz/corpus/crash-c1e3b9cd71f83cc0de5ab4c0e3db39316cd5c6c0
@@ -0,0 +1 @@
+±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±±
diff --git a/util.c b/util.c
index e8627589b49a..419ed16a52d5 100644
--- a/util.c
+++ b/util.c
@@ -88,7 +88,7 @@ postdecode_fields(char *postbuf, ssize_t len, char **fields, int n_fields)
 	char *p;
 	int i, field, found = 0;
 
-	for (p = postbuf, i = 0; i <= len; i++)
+	for (p = postbuf, i = 0; i < len; i++)
 	{
 		if (postbuf[i] == '=')
 		{