Jeff King
3c7a31204f
An mmfile_t stores its size as a signed long, but the more natural type for a buffer size is size_t. This not only limits the size of entry we can hold, but also creates some possible integer overflow issues. For example, read_mmfile() checks that the file size fits in a size_t before allocating, but then assigns it to a long. Likewise, read_mmblob() and fill_mmfile() copy sizes from other types without checking that they fit. On LP64 systems like Linux, this is mostly academic. You could wrap to a negative long value, but you'd need an object that's 2^63 bytes, which is impractical. But on an LLP64 system like Windows, a 2^31+1-byte blob could perhaps cause mischief. We do prevent large values from entering the xdiff code due to MAX_XDIFF_SIZE (which is itself marked as unsigned, so we'd convert any negative "long" back to a large unsigned value). But if you ask for binary diffs, that negative long value could instead be converted to a huge 64-bit size_t when passed to memcmp(), diff_delta(), etc. So probably there are paths that can cause an out-of-bounds read, given the right set of options, but I didn't really dig for them. On a 32-bit system things are less clear. Because "long" and "size_t" have the same width, any time we implicitly convert to size_t, we should get back the original size (even if the intermediate "long" is itself negative). Probably iterating using a long could be a problem, but most of that happens inside xdiff, which is protected by MAX_XDIFF_SIZE (which, again, compares in the unsigned space). Let's just use the obvious size_t type for counting the bytes. I suspect you could still find truncation problems on LLP64 systems due to the use of "unsigned long" throughout the code, but that's a larger problem. This should at least nudge us in the right direction. Note that we have to update the printf format in emit_binary_diff_body() to accommodate the new type. Curiously it was using "%lu", even though the type was signed (I guess compiler printf-linting is happy enough if just the width of the format and the type match). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
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See Documentation/gittutorial.adoc to get started, then see
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If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
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CVS users may also want to read Documentation/gitcvs-migration.adoc
(man gitcvs-migration or git help cvs-migration if git is
installed).
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The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks