Re* [PATCH v7 1/1] sideband: highlight keywords in remote sideband output
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Aug 17, 2018, 18:44 UTC
- Message-ID
- <xmqq8t54bzo4.fsf_-_@gitster-ct.c.googlers.com>
- In-Reply-To
- <xmqqd0ugc07x.fsf@gitster-ct.c.googlers.com>
Junio C Hamano <gitster@pobox.com> writes:
Show 16 quoted lines
> This loop can run out of bytes in src in search of non-space before
> n gets to zero or negative, and when that happens ...
>
>> + for (i = 0; i < ARRAY_SIZE(keywords); i++) {
>> + struct keyword_entry *p = keywords + i;
>> + int len = strlen(p->keyword);
>> + /*
>> + * Match case insensitively, so we colorize output from existing
>> + * servers regardless of the case that they use for their
>> + * messages. We only highlight the word precisely, so
>> + * "successful" stays uncolored.
>> + */
>> + if (!strncasecmp(p->keyword, src, len) && !isalnum(src[len])) {
>
> ... these access src[] beyond the end of what the caller intended to
> show us, and also ...Actually, leaving when !n before this loop is insufficient. src[] may have 2 bytes "in" remaining, and we may be trying to see if it begins with "info", for example, and using strncasecmp() with len==4 would of course read beyond the end of src[].
-- >8 -- Subject: sideband: do not read beyond the end of input
The caller of maybe_colorize_sideband() gives a counted buffer <src,n>, but the callee checked *src as if it were a NUL terminated buffer. If src[] had all isspace() bytes in it, we would have made n negative, and then (1) called number of strncasecmp() to see if the remaining bytes in src[] matched keywords, reading beyond the end of the array, and/or (2) called strbuf_add() with negative count, most likely triggering the "you want to use way too much memory" error due to unsigned integer overflow.
Signed-off-by: Junio C Hamano <gitster@pobox.com> --- sideband.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/sideband.c b/sideband.c index 1c6bb0e25b..372039247f 100644 --- a/sideband.c +++ b/sideband.c @@ -75,7 +75,7 @@ static void maybe_colorize_sideband(struct strbuf *dest, const char *src, int n) return; } - while (isspace(*src)) { + while (0 < n && isspace(*src)) { strbuf_addch(dest, *src); src++; n--; @@ -84,6 +84,9 @@ static void maybe_colorize_sideband(struct strbuf *dest, const char *src, int n) for (i = 0; i < ARRAY_SIZE(keywords); i++) { struct keyword_entry *p = keywords + i; int len = strlen(p->keyword); + + if (n <= len) + continue; /* * Match case insensitively, so we colorize output from existing * servers regardless of the case that they use for their @@ -100,8 +103,8 @@ static void maybe_colorize_sideband(struct strbuf *dest, const char *src, int n) } } - strbuf_add(dest, src, n); - + if (0 < n) + strbuf_add(dest, src, n); }