After the first fix to the struct package I found another similar
problem, which is fixed by this patch. It could be reproduced easily by
running the following script:
return struct.unpack('f', "xxxxxxxxxxxxx",-3)
The above will access bytes before the 'data' pointer.
@soloestoy sent me this additional fixes, after searching for similar
problems to the one reported in mp_pack(). I'm committing the changes
because it was not possible during to make a public PR to protect Redis
users and give Redis providers some time to patch their systems.
During an auditing Apple found that the "struct" Lua package
we ship with Redis (http://www.inf.puc-rio.br/~roberto/struct/) contains
a security problem. A bound-checking statement fails because of integer
overflow. The bug exists since we initially integrated this package with
Lua, when scripting was introduced, so every version of Redis with
EVAL/EVALSHA capabilities exposed is affected.
Instead of just fixing the bug, the library was updated to the latest
version shipped by the author.
During an auditing effort, the Apple Vulnerability Research team discovered
a critical Redis security issue affecting the Lua scripting part of Redis.
-- Description of the problem
Several years ago I merged a pull request including many small changes at
the Lua MsgPack library (that originally I authored myself). The Pull
Request entered Redis in commit 90b6337c1, in 2014.
Unfortunately one of the changes included a variadic Lua function that
lacked the check for the available Lua C stack. As a result, calling the
"pack" MsgPack library function with a large number of arguments, results
into pushing into the Lua C stack a number of new values proportional to
the number of arguments the function was called with. The pushed values,
moreover, are controlled by untrusted user input.
This in turn causes stack smashing which we believe to be exploitable,
while not very deterministic, but it is likely that an exploit could be
created targeting specific versions of Redis executables. However at its
minimum the issue results in a DoS, crashing the Redis server.
-- Versions affected
Versions greater or equal to Redis 2.8.18 are affected.
-- Reproducing
Reproduce with this (based on the original reproduction script by
Apple security team):
https://gist.github.com/antirez/82445fcbea6d9b19f97014cc6cc79f8a
-- Verification of the fix
The fix was tested in the following way:
1) I checked that the problem is no longer observable running the trigger.
2) The Lua code was analyzed to understand the stack semantics, and that
actually enough stack is allocated in all the cases of mp_pack() calls.
3) The mp_pack() function was modified in order to show exactly what items
in the stack were being set, to make sure that there is no silent overflow
even after the fix.
-- Credits
Thank you to the Apple team and to the other persons that helped me
checking the patch and coordinating this communication.
problems fixed:
* failing to read fragmentation information from jemalloc
* overflow in jemalloc fragmentation hint to the defragger
* test suite not triggering eviction after population
The original jemalloc source tree was modified to:
1. Remove the configure error that prevents nested builds.
2. Insert the Redis private Jemalloc API in order to allow the
Redis fragmentation function to work.
The problem was fixed in antirez/linenoise repository applying a patch
contributed by @lamby. Here the new version is updated in the Redis
source tree.
Close#1418Close#3322
They were under /deps since they originate from a different source tree,
however at this point they are very modified and we took ownership of
both the files making changes, fixing bugs, so there is no upgrade path
from the original code tree.
Given that, better to move the code under /src with proper dependencies
and with a more simpler editing experience.
I'm the author of this line but I can't see a good reason for it to
don't be a typo, a step of 26 should be valid with 52 bits per
coordinate, moreover the line was:
if (step > 26) step = 25;
So a step of 26 was actually already used, except when one of 27 was
computed (which is invalid) only then it was trimmed to 25 instead of
26.
All tests passing after the change.
This change is documented in deps/README.md but was lost in one way or
the other, neutralizing the benefits of 24 bytes size classes (and
others).
Close#3208.
Redis-cli handles the debugger "eval" command in a special way since
sdssplitargs() would not be ok: we need to send the Redis debugger the
whole Lua script without any parsing. However in order to later free the
argument vector inside redis-cli using just sdsfreesplitres(), we need
to allocate the array of SDS pointers using the same allocator SDS is
using, that may differ to what Redis is using.
So now a newer version of SDS exports sds_malloc() and other allocator
functions to give access, to the program it is linked to, the allocator
used internally by SDS.
This gives us a 24 bytes size class which is dict.c dictEntry size, thus
improving the memory efficiency of Redis significantly.
Moreover other non 16 bytes aligned tiny classes are added that further
reduce the fragmentation of the allocator.
Technically speaking LG_QUANTUM should be 4 on i386 / AMD64 because of
SSE types and other 16 bytes types, however we don't use those, and our
jemalloc only targets Redis.
New versions of Jemalloc will have an explicit configure switch in order
to specify the quantum value for a platform without requiring any change
to the Jemalloc source code: we'll switch to this system when available.
This change was originally proposed by Oran Agra (@oranagra) as a change
to the Jemalloc script to generate the size classes define. We ended
doing it differently by changing LG_QUANTUM since it is apparently the
supported Jemalloc method to obtain a 24 bytes size class, moreover it
also provides us other potentially useful size classes.
Related to issue #2510.
Instead of successive divisions in iteration the new code uses bitwise
magic to interleave / deinterleave two 32bit values into a 64bit one.
All tests still passing and is measurably faster, so worth it.
