# [PATCH] off-by-one bugs found by valgrind 4 messages from 2005-12-21 to 2005-12-21. Participants: Pavel Roskin, Junio C Hamano, H. Peter Anvin. Thread: https://gitlist.dev/t/2899 ## Pavel Roskin, 2005-12-21 20:35 Subject: [PATCH] off-by-one bugs found by valgrind Message-ID: <1135197348.3046.7.camel@dv> URL: https://gitlist.dev/e/1135197348.3046.7.camel%40dv ``` Insufficient memory is allocated in index-pack.c to hold the *.idx name. One more byte should be allocated to hold the terminating 0. quote_c_style_counted() in quote.c uses a dangerous construct, when a variable is incremented once and used twice in the same expression. Convert this construct to a more traditional form of the for loop. Signed-off-by: Pavel Roskin diff --git a/index-pack.c b/index-pack.c index 785fe71..d4ce3af 100644 --- a/index-pack.c +++ b/index-pack.c @@ -440,7 +440,7 @@ int main(int argc, char **argv) if (len < 5 || strcmp(pack_name + len - 5, ".pack")) die("packfile name '%s' does not end with '.pack'", pack_name); - index_name_buf = xmalloc(len - 1); + index_name_buf = xmalloc(len); memcpy(index_name_buf, pack_name, len - 5); strcpy(index_name_buf + len - 5, ".idx"); index_name = index_name_buf; diff --git a/quote.c b/quote.c index 76eb144..00297b5 100644 --- a/quote.c +++ b/quote.c @@ -126,8 +126,10 @@ static int quote_c_style_counted(const c if (!no_dq) EMIT('"'); - for (sp = name; (ch = *sp++) && (sp - name) <= namelen; ) { - + for (sp = name; sp < name + namelen; sp++) { + ch = *sp; + if (!ch) + break; if ((ch < ' ') || (ch == '"') || (ch == '\\') || (ch == 0177)) { needquote = 1; -- Regards, Pavel Roskin ``` ## Junio C Hamano, 2005-12-21 20:59 Subject: Re: [PATCH] off-by-one bugs found by valgrind Message-ID: <7vr7865fq5.fsf@assigned-by-dhcp.cox.net> URL: https://gitlist.dev/e/7vr7865fq5.fsf%40assigned-by-dhcp.cox.net In-Reply-To: <1135197348.3046.7.camel@dv> ``` Pavel Roskin writes: > Insufficient memory is allocated in index-pack.c to hold the *.idx name. > One more byte should be allocated to hold the terminating 0. Thanks. > quote_c_style_counted() in quote.c uses a dangerous construct, when a > variable is incremented once and used twice in the same expression. Sorry, I do not follow you. Isn't && a sequence point? > - for (sp = name; (ch = *sp++) && (sp - name) <= namelen; ) { > - > + for (sp = name; sp < name + namelen; sp++) { ``` ## H. Peter Anvin, 2005-12-21 21:17 Subject: Re: [PATCH] off-by-one bugs found by valgrind Message-ID: <43A9C654.2010009@zytor.com> URL: https://gitlist.dev/e/43A9C654.2010009%40zytor.com In-Reply-To: <7vr7865fq5.fsf@assigned-by-dhcp.cox.net> ``` Junio C Hamano wrote: > Pavel Roskin writes: > > >>Insufficient memory is allocated in index-pack.c to hold the *.idx name. >>One more byte should be allocated to hold the terminating 0. > > Thanks. > > >>quote_c_style_counted() in quote.c uses a dangerous construct, when a >>variable is incremented once and used twice in the same expression. > > Sorry, I do not follow you. Isn't && a sequence point? > && is a sequence point. The code is techically fine, but it's harder than necessary to read. -hpa ``` ## Pavel Roskin, 2005-12-21 21:47 Subject: Re: [PATCH] off-by-one bugs found by valgrind Message-ID: <1135201641.15567.7.camel@dv> URL: https://gitlist.dev/e/1135201641.15567.7.camel%40dv In-Reply-To: <43A9C654.2010009@zytor.com> ``` On Wed, 2005-12-21 at 13:17 -0800, H. Peter Anvin wrote: > >>quote_c_style_counted() in quote.c uses a dangerous construct, when a > >>variable is incremented once and used twice in the same expression. > > > > Sorry, I do not follow you. Isn't && a sequence point? The patch is right, but my comment was wrong, sorry. The actual problem detected by valgrind is that sp is dereferenced before it's checked for the upper boundary. So, if e.g. namelen is 6, the code reads name[6] into ch and then leaves the loop. > && is a sequence point. The code is techically fine, but it's harder > than necessary to read. That alone should be a good reason to apply this patch. -- Regards, Pavel Roskin ```