threads / patch / 8610

patchpp_header(): work around possible memory corruption

Subject: [PATCH/RFH] pp_header(): work around possible memory corruption

## tl;dr

4 messages between Jun 15, 2007 and Jun 23, 2007. Diffs are folded; open one to read it.

replies: 3people: 2as markdown or json

Johannes Schindelin· Jun 15, 2007, 12:19 UTC · lore

add_user_info() possibly adds way more than just the commit header line. In fact, it sometimes needs so much more space that there is a buffer overrun, leading to an ugly crash. For example, the date is printed in its own line, and usually takes up more space than the equivalent Unix epoch.

So, for good measure, add 80 characters (a full line) to the allocated space, in addition to the header line length.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>

---

	I have no idea if 80 is a good value, and if other places
	need an equivalent fix up, too.

	But I needed this patch in a hurry...

 commit.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

Show changes to commit.c +2 −2

diff --git a/commit.c b/commit.c
index f778bf4..03436b1 100644
--- a/commit.c
+++ b/commit.c
@@ -997,7 +997,7 @@ static void pp_header(enum cmit_fmt fmt,
 			len = linelen;
 			if (fmt == CMIT_FMT_EMAIL)
 				len = bound_rfc2047(linelen, encoding);
-			ALLOC_GROW(*buf_p, *ofs_p + len, *space_p);
+			ALLOC_GROW(*buf_p, *ofs_p + len + 80, *space_p);
 			dst = *buf_p + *ofs_p;
 			*ofs_p += add_user_info("Author", fmt, dst,
 						line + 7, dmode, encoding);
@@ -1008,7 +1008,7 @@ static void pp_header(enum cmit_fmt fmt,
 			len = linelen;
 			if (fmt == CMIT_FMT_EMAIL)
 				len = bound_rfc2047(linelen, encoding);
-			ALLOC_GROW(*buf_p, *ofs_p + len, *space_p);
+			ALLOC_GROW(*buf_p, *ofs_p + len + 80, *space_p);
 			dst = *buf_p + *ofs_p;
 			*ofs_p += add_user_info("Commit", fmt, dst,
 						line + 10, dmode, encoding);

Junio C Hamano· Jun 16, 2007, 05:31 UTC · re: Johannes Schindelin · lore

Re: [PATCH/RFH] pp_header(): work around possible memory corruption

At least the older humongous pretty_print_commit() got separated into manageable chunks, and I was happy. I was just too lazy when refactoring the code and stopped there.

The right fix is to propagate the "realloc as needed" callchain into add_user_info(), instead of having "this should be enough" there. These two you touched are the only two callsite of that static function.

Johannes Schindelin· Jun 19, 2007, 00:19 UTC · re: Junio C Hamano · lore

Re: [PATCH/RFH] pp_header(): work around possible memory corruption

Hi,

On Fri, 15 Jun 2007, Junio C Hamano wrote:

> At least the older humongous pretty_print_commit() got separated into 
> manageable chunks, and I was happy.  I was just too lazy when 
> refactoring the code and stopped there.

That's perfectly okay. This is why you parked it in 'next', I guess.

> The right fix is to propagate the "realloc as needed" callchain into 
> add_user_info(), instead of having "this should be enough" there.  
> These two you touched are the only two callsite of that static function.

Right. As I said, I was in a hurry, and could not research it properly. Besides, now that you gave me the proper pointer, I can take care about it tomorrow, unless somebody else is faster.

Ciao, Dscho

Johannes Schindelin· Jun 23, 2007, 23:32 UTC · re: Junio C Hamano · lore

Re: [PATCH/RFH] pp_header(): work around possible memory corruption

Hi,

On Fri, 15 Jun 2007, Junio C Hamano wrote:

> At least the older humongous pretty_print_commit() got separated into 
> manageable chunks, and I was happy.  I was just too lazy when 
> refactoring the code and stopped there.

Understandable.

> The right fix is to propagate the "realloc as needed" callchain into 
> add_user_info(), instead of having "this should be enough" there.  
> These two you touched are the only two callsite of that static function.

I had a go at this, but unfortunately I do not understand enough of what is going on there. For example, add_rfc2047() sometimes quotes some text. I have no idea what a conservative estimate of the growth is, so I cannot continue there.

Sorry, Dscho