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Ziplists had a bug that was discovered while investigating a different issue, resulting in a corrupted ziplist representation, and a likely segmentation foult and/or data corruption of the last element of the ziplist, once the ziplist is accessed again. The bug happens when a specific set of insertions / deletions is performed so that an entry is encoded to have a "prevlen" field (the length of the previous entry) of 5 bytes but with a count that could be encoded in a "prevlen" field of a since byte. This could happen when the "cascading update" process called by ziplistInsert()/ziplistDelete() in certain contitious forces the prevlen to be bigger than necessary in order to avoid too much data moving around. Once such an entry is generated, inserting a very small entry immediately before it will result in a resizing of the ziplist for a count smaller than the current ziplist length (which is a violation, inserting code expects the ziplist to get bigger actually). So an FF byte is inserted in a misplaced position. Moreover a realloc() is performed with a count smaller than the ziplist current length so the final bytes could be trashed as well. SECURITY IMPLICATIONS: Currently it looks like an attacker can only crash a Redis server by providing specifically choosen commands. However a FF byte is written and there are other memory operations that depend on a wrong count, so even if it is not immediately apparent how to mount an attack in order to execute code remotely, it is not impossible at all that this could be done. Attacks always get better... and we did not spent enough time in order to think how to exploit this issue, but security researchers or malicious attackers could.
Where to find complete Redis documentation? ------------------------------------------- This README is just a fast "quick start" document. You can find more detailed documentation at http://redis.io Building Redis -------------- Redis can be compiled and used on Linux, OSX, OpenBSD, NetBSD, FreeBSD. We support big endian and little endian architectures. It may compile on Solaris derived systems (for instance SmartOS) but our support for this platform is "best effort" and Redis is not guaranteed to work as well as in Linux, OSX, and *BSD there. It is as simple as: % make You can run a 32 bit Redis binary using: % make 32bit After building Redis is a good idea to test it, using: % make test Fixing build problems with dependencies or cached build options —-------- Redis has some dependencies which are included into the "deps" directory. "make" does not rebuild dependencies automatically, even if something in the source code of dependencies is changes. When you update the source code with `git pull` or when code inside the dependencies tree is modified in any other way, make sure to use the following command in order to really clean everything and rebuild from scratch: make distclean This will clean: jemalloc, lua, hiredis, linenoise. Also if you force certain build options like 32bit target, no C compiler optimizations (for debugging purposes), and other similar build time options, those options are cached indefinitely until you issue a "make distclean" command. Fixing problems building 32 bit binaries --------- If after building Redis with a 32 bit target you need to rebuild it with a 64 bit target, or the other way around, you need to perform a "make distclean" in the root directory of the Redis distribution. In case of build errors when trying to build a 32 bit binary of Redis, try the following steps: * Install the packages libc6-dev-i386 (also try g++-multilib). * Try using the following command line instead of "make 32bit": make CFLAGS="-m32 -march=native" LDFLAGS="-m32" Allocator --------- Selecting a non-default memory allocator when building Redis is done by setting the `MALLOC` environment variable. Redis is compiled and linked against libc malloc by default, with the exception of jemalloc being the default on Linux systems. This default was picked because jemalloc has proven to have fewer fragmentation problems than libc malloc. To force compiling against libc malloc, use: % make MALLOC=libc To compile against jemalloc on Mac OS X systems, use: % make MALLOC=jemalloc Verbose build ------------- Redis will build with a user friendly colorized output by default. If you want to see a more verbose output use the following: % make V=1 Running Redis ------------- To run Redis with the default configuration just type: % cd src % ./redis-server If you want to provide your redis.conf, you have to run it using an additional parameter (the path of the configuration file): % cd src % ./redis-server /path/to/redis.conf It is possible to alter the Redis configuration passing parameters directly as options using the command line. Examples: % ./redis-server --port 9999 --slaveof 127.0.0.1 6379 % ./redis-server /etc/redis/6379.conf --loglevel debug All the options in redis.conf are also supported as options using the command line, with exactly the same name. Playing with Redis ------------------ You can use redis-cli to play with Redis. Start a redis-server instance, then in another terminal try the following: % cd src % ./redis-cli redis> ping PONG redis> set foo bar OK redis> get foo "bar" redis> incr mycounter (integer) 1 redis> incr mycounter (integer) 2 redis> You can find the list of all the available commands here: http://redis.io/commands Installing Redis ----------------- In order to install Redis binaries into /usr/local/bin just use: % make install You can use "make PREFIX=/some/other/directory install" if you wish to use a different destination. Make install will just install binaries in your system, but will not configure init scripts and configuration files in the appropriate place. This is not needed if you want just to play a bit with Redis, but if you are installing it the proper way for a production system, we have a script doing this for Ubuntu and Debian systems: % cd utils % ./install_server.sh The script will ask you a few questions and will setup everything you need to run Redis properly as a background daemon that will start again on system reboots. You'll be able to stop and start Redis using the script named /etc/init.d/redis_<portnumber>, for instance /etc/init.d/redis_6379. Code contributions --- Note: by contributing code to the Redis project in any form, including sending a pull request via Github, a code fragment or patch via private email or public discussion groups, you agree to release your code under the terms of the BSD license that you can find in the COPYING file included in the Redis source distribution. Please see the CONTRIBUTING file in this source distribution for more information. Enjoy!
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