Summary:
Add a method to set the release to OS value as the system runs,
and allow this to be set differently in the primary and the secondary.
Also, add a default value to use for primary and secondary. This
allows Android to have a default that is different for
primary/secondary.
Update mallopt to support setting the release to OS value.
Reviewers: pcc, cryptoad
Reviewed By: cryptoad
Subscribers: cryptoad, jfb, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D74448
Summary:
Due to Unity, we had to reduce our region sizes, but in some rare
situations, some programs (mostly tests AFAICT) manage to fill up
a region for a given size class.
So this adds a workaround for that attempts to allocate the block
from the immediately larger size class, wasting some memory but
allowing the application to keep going.
Reviewers: pcc, eugenis, cferris, hctim, morehouse
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D74567
Add an optional table lookup after the existing logarithm computation
for MidSize < Size <= MaxSize during size -> class lookups. The lookup is
O(1) due to indexing a precomputed (via constexpr) table based on a size
table. Switch to this approach for the Android size class maps.
Other approaches considered:
- Binary search was found to have an unacceptable (~30%) performance cost.
- An approach using NEON instructions (see older version of D73824) was found
to be slightly slower than this approach on newer SoCs but significantly
slower on older ones.
By selecting the values in the size tables to minimize wastage (for example,
by passing the malloc_info output of a target program to the included
compute_size_class_config program), we can increase the density of allocations
at a small (~0.5% on bionic malloc_sql_trace as measured using an identity
table) performance cost.
Reduces RSS on specific Android processes as follows (KB):
Before After
zygote (median of 50 runs) 26836 26792 (-0.2%)
zygote64 (median of 50 runs) 30384 30076 (-1.0%)
dex2oat (median of 3 runs) 375792 372952 (-0.8%)
I also measured the amount of whole-system idle dirty heap on Android by
rebooting the system and then running the following script repeatedly until
the results were stable:
for i in $(seq 1 50); do grep -A5 scudo: /proc/*/smaps | grep Pss: | cut -d: -f2 | awk '{s+=$1} END {print s}' ; sleep 1; done
I did this 3 times both before and after this change and the results were:
Before: 365650, 356795, 372663
After: 344521, 356328, 342589
These results are noisy so it is hard to make a definite conclusion, but
there does appear to be a significant effect.
On other platforms, increase the sizes of all size classes by a fixed offset
equal to the size of the allocation header. This has also been found to improve
density, since it is likely for allocation sizes to be a power of 2, which
would otherwise waste space by pushing the allocation into the next size class.
Differential Revision: https://reviews.llvm.org/D73824
This lets us remove two pointer indirections (one by removing the pointer,
and another by making the AllocatorPtr declaration hidden) in the C++ wrappers.
Differential Revision: https://reviews.llvm.org/D74356
Summary:
This tweaks some behaviors of the allocator wrt 32-bit, notably
tailoring the size-class map.
I had to remove a `printStats` from `__scudo_print_stats` since when
within Bionic they share the same slot so they can't coexist at the
same time. I have to find a solution for that later, but right now we
are not using the Svelte configuration.
Reviewers: rengolin
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D74178
The class is only used in SizeClassAllocator32 in 64-bit mode, but we don't
use that class in 64-bit mode.
Differential Revision: https://reviews.llvm.org/D74099
Summary:
Forewarning: This patch looks big in #LOC changed. I promise it's not that bad, it just moves a lot of content from one file to another. I've gone ahead and left inline comments on Phabricator for sections where this has happened.
This patch:
1. Introduces the crash handler API (crash_handler_api.h).
2. Moves information required for out-of-process crash handling into an AllocatorState. This is a trivially-copied POD struct that designed to be recovered from a deceased process, and used by the crash handler to create a GWP-ASan report (along with the other trivially-copied Metadata struct).
3. Implements the crash handler API using the AllocatorState and Metadata.
4. Adds tests for the crash handler.
5. Reimplements the (now optionally linked by the supporting allocator) in-process crash handler (i.e. the segv handler) using the new crash handler API.
6. Minor updates Scudo & Scudo Standalone to fix compatibility.
7. Changed capitalisation of errors (e.g. /s/Use after free/Use After Free).
Reviewers: cryptoad, eugenis, jfb
Reviewed By: eugenis
Subscribers: merge_guards_bot, pcc, jfb, dexonsmith, mgorny, cryptoad, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73557
Summary:
I tried to move the `madvise` calls outside of one of the secondary
mutexes, but this backfired. There is situation when a low release
interval is set combined with secondary pressure that leads to a race:
a thread can get a block from the cache, while another thread is
`madvise`'ing that block, resulting in a null header.
I changed the secondary race test so that this situation would be
triggered, and moved the release into the cache mutex scope.
Reviewers: cferris, pcc, eugenis, hctim, morehouse
Subscribers: jfb, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D74072
By subtracting 1 from Size at the beginning we can simplify the
subsequent calculations. This also saves 4 instructions on aarch64
and 9 instructions on x86_64, but seems to be perf neutral.
Differential Revision: https://reviews.llvm.org/D73936
As a result of recent changes to the Android size classes, the malloc_free_loop
benchmark started exhausting the 8192 size class at 32768 iterations. To avoid
this problem (and to make the test more realistic), change the benchmark to
use a variety of size classes.
Differential Revision: https://reviews.llvm.org/D73918
Summary:
This changes a couple of parameters in the default Android config to
address some performance and memory footprint issues (well to be closer
to the default Bionic allocator numbers).
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73750
Summary:
The Secondary's cache needs to be released when the Combined's
`releaseToOS` function is called (via `M_PURGE`) for example,
which this CL adds.
Additionally, if doing a forced release, we'll release the
transfer batch class as well since now we can do that.
There is a couple of other house keeping changes as well:
- read the page size only once in the Secondary Cache `store`
- remove the interval check for `CanRelease`: we are going to
make that configurable via `mallopt` so this needs not be
set in stone there.
Reviewers: cferris, hctim, pcc, eugenis
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73730
Summary:
A couple of seemingly innocuous changes ended up having a large impact
on the 32-bit performance. I still have to make those configurable at
some point, but right now it will have to do.
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73658
Summary:
Zygote & children's stderr is lost, so use Bionic's provided allocation
free syslog function for `outputRaw`. Get rid of the mutex as it's not
vital and could cause issues with `fork`.
Reviewers: cferris, pcc, eugenis, hctim, morehouse
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73561
Summary:
This CL changes multiple things to improve performance (notably on
Android).We introduce a cache class for the Secondary that is taking
care of this mechanism now.
The changes:
- change the Secondary "freelist" to an array. By keeping free secondary
blocks linked together through their headers, we were keeping a page
per block, which isn't great. Also we know touch less pages when
walking the new "freelist".
- fix an issue with the freelist getting full: if the pattern is an ever
increasing size malloc then free, the freelist would fill up and
entries would not be used. So now we empty the list if we get to many
"full" events;
- use the global release to os interval option for the secondary: it
was too costly to release all the time, particularly for pattern that
are malloc(X)/free(X)/malloc(X). Now the release will only occur
after the selected interval, when going through the deallocate path;
- allow release of the `BatchClassId` class: it is releasable, we just
have to make sure we don't mark the batches containing batches
pointers as free.
- change the default release interval to 1s for Android to match the
current Bionic allocator configuration. A patch is coming up to allow
changing it through `mallopt`.
- lower the smallest class that can be released to `PageSize/64`.
Reviewers: cferris, pcc, eugenis, morehouse, hctim
Subscribers: phosek, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73507
Summary:
This is an Android-specific interface for iterating over all live
allocations in a memory range.
Reviewers: hctim, cferris
Subscribers: mgorny, mgrang, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73305
Summary:
* Implement enable() and disable() in GWP-ASan.
* Setup atfork handler.
* Improve test harness sanity and re-enable GWP-ASan in Scudo.
Scudo_standalone disables embedded GWP-ASan as necessary around fork().
Standalone GWP-ASan sets the atfork handler in init() if asked to. This
requires a working malloc(), therefore GWP-ASan initialization in Scudo
is delayed to the post-init callback.
Test harness changes are about setting up a single global instance of
the GWP-ASan allocator so that pthread_atfork() does not create
dangling pointers.
Test case shamelessly stolen from D72470.
Reviewers: cryptoad, hctim, jfb
Subscribers: mgorny, jfb, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73294
Summary:
Unity is making irresponsible assumptions as to how clumped up memory
should be. With larger regions, we break those, resulting in errors
like:
"Using memoryadresses from more that 16GB of memory"
This is unfortunately one of those situations where we have to bend to
existing code because we doubt it's going to change any time soon.
128MB should be enough, but we could be flirting with OOMs in the
higher class sizes.
Reviewers: cferris, eugenis, hctim, morehouse, pcc
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73143
Summary:
In some configuration, `sched_getaffinity` can fail. Some reasons for
that being the lack of `CAP_SYS_NICE` capability or some syscall
filtering and so on.
This should not be fatal to the allocator, so in this situation, we
will fallback to the `MaxTSDCount` value specified in the allocator
configuration.
Reviewers: cferris, eugenis, hctim, morehouse, pcc
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D73055
When the hardware and operating system support the ARM Memory Tagging
Extension, tag primary allocation granules with a random tag. The granules
either side of the allocation are tagged with tag 0, which is normally
excluded from the set of tags that may be selected randomly. Memory is
also retagged with a random tag when it is freed, and we opportunistically
reuse the new tag when the block is reused to reduce overhead. This causes
linear buffer overflows to be caught deterministically and non-linear buffer
overflows and use-after-free to be caught probabilistically.
This feature is currently only enabled for the Android allocator
and depends on an experimental Linux kernel branch available here:
https://github.com/pcc/linux/tree/android-experimental-mte
All code that depends on the kernel branch is hidden behind a macro,
ANDROID_EXPERIMENTAL_MTE. This is the same macro that is used by the Android
platform and may only be defined in non-production configurations. When the
userspace interface is finalized the code will be updated to use the stable
interface and all #ifdef ANDROID_EXPERIMENTAL_MTE will be removed.
Differential Revision: https://reviews.llvm.org/D70762
Summary:
fork() wasn't well (or at all) supported in Scudo. This materialized
in deadlocks in children.
In order to properly support fork, we will lock the allocator pre-fork
and unlock it post-fork in parent and child. This is done via a
`pthread_atfork` call installing the necessary handlers.
A couple of things suck here: this function allocates - so this has to
be done post initialization as our init path is not reentrance, and it
doesn't allow for an extra pointer - so we can't pass the allocator we
are currently working with.
In order to work around this, I added a post-init template parameter
that gets executed once the allocator is initialized for the current
thread. Its job for the C wrappers is to install the atfork handlers.
I reorganized a bit the impacted area and added some tests, courtesy
of cferris@ that were deadlocking prior to this fix.
Subscribers: jfb, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D72470
Summary:
Some Android builds that we are interested in define `__BIONIC__`
but not `__ANDROID__`, so expand `SCUDO_ANDROID` to encompass those.
Reviewers: cferris, hctim, pcc, eugenis, morehouse
Subscribers: krytarowski, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D71772
Summary:
In order to implement `malloc_{enable|disable}` we were just disabling
(or really locking) the Primary and the Secondary. That meant that
allocations could still be serviced from the TSD as long as the cache
wouldn't have to be filled from the Primary.
This wasn't working out for Android tests, so this change implements
registry disabling (eg: locking) so that `getTSDAndLock` doesn't
return a TSD if the allocator is disabled. This also means that the
Primary doesn't have to be disabled in this situation.
For the Shared Registry, we loop through all the TSDs and lock them.
For the Exclusive Registry, we add a `Disabled` boolean to the Registry
that forces `getTSDAndLock` to use the Fallback TSD instead of the
thread local one. Disabling the Registry is then done by locking the
Fallback TSD and setting the boolean in question (I don't think this
needed an atomic variable but I might be wrong).
I clang-formatted the whole thing as usual hence the couple of extra
whiteline changes in this CL.
Reviewers: cferris, pcc, hctim, morehouse, eugenis
Subscribers: jfb, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D71719
Turns out that gtest in LLVM is only 1.8.0 (the newest version 1.10.0)
supports the GTEST_SKIP() macro, and apparently I didn't build w/o
GWP-ASan.
Should fix the GN bot, as well as any bots that may spuriously break on
platforms where the code wasn't correctly ifdef'd out as well.
Summary:
Adds GWP-ASan to Scudo standalone. Default parameters are pulled across from the
GWP-ASan build. No backtrace support as of yet.
Reviewers: cryptoad, eugenis, pcc
Reviewed By: cryptoad
Subscribers: merge_guards_bot, mgorny, #sanitizers, llvm-commits, cferris, vlad.tsyrklevich, pcc
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D71229
Instead of testing whether the pointer is aligned, just align it
unconditionally and compare it to the original pointer.
This moves the computation of UserPtr up to before we start preparing the
header, so that the memory tagging code will be able to read the original
header containing the bounds of the previous allocation before it gets
potentially clobbered by the pointer realignment code.
Differential Revision: https://reviews.llvm.org/D71292
With tag-on-free we will need to get the chunk of a deallocated block. Change
getChunkFromBlock() so that it doesn't check that the chunk is allocated,
and move the check into the caller, so that it can be reused for this purpose.
Differential Revision: https://reviews.llvm.org/D71291
Summary:
The function was only defined for x86 and arm families, which ends
up being an issue for PPC in g3.
Define the function, simply returning `false` for "other"
architectures.
Reviewers: hctim, pcc, cferris, eugenis, vitalybuka
Subscribers: kristof.beyls, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D71223
The test ScudoWrappersCTest.Realloc expects realloc of memalign to work on
Android, but this relies on dealloc_type_mismatch being set to false. Commit
0d3d4d3b0 caused us to start setting it to true in the C wrapper tests,
which broke the test. Set it to the correct value on Android.
Differential Revision: https://reviews.llvm.org/D71078
The Android headers don't provide a declaration of valloc or pvalloc, so we
need to declare them ourselves.
Differential Revision: https://reviews.llvm.org/D71077
Summary:
In order to be compliant with tcmalloc's extension ownership
determination function, we have to expose a function that will
say if a chunk was allocated by us.
As to whether or not this has security consequences: someone
able to call this function repeatedly could use it to determine
secrets (cookie) or craft a valid header. So this should not be
exposed directly to untrusted user input.
Add related tests.
Additionally clang-format caught a few things to change.
Reviewers: hctim, pcc, cferris, eugenis, vitalybuka
Subscribers: JDevlieghere, jfb, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D70908
This test was previously effectively doing:
P = malloc(X); write X bytes to P; P = realloc(P, X - Y); P = realloc(P, X)
and expecting that all X bytes stored to P would still be identical after
the final realloc.
This happens to be true for the current scudo implementation of realloc,
but is not guaranteed to be true by the C standard ("Any bytes in the new
object beyond the size of the old object have indeterminate values.").
This implementation detail will change with the new memory tagging support,
which unconditionally zeros newly allocated granules when memory tagging
is enabled. Fix this by limiting the number of bytes that we test to the
minimum size that we realloc the allocation to.
Differential Revision: https://reviews.llvm.org/D70761
The macros INLINE and COMPILER_CHECK always expand to the same thing (inline
and static_assert respectively). Both expansions are standards compliant C++
and are used consistently in the rest of LLVM, so let's improve consistency
with the rest of LLVM by replacing them with the expansions.
Differential Revision: https://reviews.llvm.org/D70793
Otherwise, we will hit a use-after-free when testing multiple instances of
the same allocator on the same thread. This only recently became a problem
with D70552 which caused us to run both ScudoCombinedTest.BasicCombined and
ScudoCombinedTest.ReleaseToOS on the unit tests' main thread.
Differential Revision: https://reviews.llvm.org/D70760
Summary:
This CL makes unit tests compatible with Fuchsia's zxtest. This
required a few changes here and there, but also unearthed some
incompatibilities that had to be addressed.
A header is introduced to allow to account for the zxtest/gtest
differences, some `#if SCUDO_FUCHSIA` are used to disable incompatible
code (the 32-bit primary, or the exclusive TSD).
It also brought to my attention that I was using
`__scudo_default_options` in different tests, which ended up in a
single binary, and I am not sure how that ever worked. So move
this to the main cpp.
Additionally fully disable the secondary freelist on Fuchsia as we do
not track VMOs for secondary allocations, so no release possible.
With some modifications to Scudo's BUILD.gn in Fuchsia:
```
[==========] 79 tests from 23 test cases ran (10280 ms total).
[ PASSED ] 79 tests
```
Reviewers: mcgrathr, phosek, hctim, pcc, eugenis, cferris
Subscribers: srhines, jfb, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D70682
Summary:
cferris@ found an issue where calling `releaseToOS` prior to any other
heap operation would lead to a crash, due to the allocator not being
properly initialized (it was discovered via `mallopt`).
The fix is to call `initThreadMaybe` prior to calling `releaseToOS` for
the Primary.
Add a test that crashes prior to fix.
Reviewers: hctim, cferris, pcc, eugenis
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D70552
Summary:
A few small improvements and optimizations:
- when refilling the free list, push back the last batch and return
the front one: this allows to keep the allocations towards the front
of the region;
- instead of using 48 entries in the shuffle array, use a multiple of
`MaxNumCached`;
- make the maximum number of batches to create on refil a constant;
ultimately it should be configurable, but that's for later;
- `initCache` doesn't need to zero out the cache, it's already done.
- it turns out that when using `||` or `&&`, the compiler is adamant
on adding a short circuit for every part of the expression. Which
ends up making somewhat annoying asm with lots of test and
conditional jump. I am changing that to bitwise `|` or `&` in two
place so that the generated code looks better. Added comments since
it might feel weird to people.
This yields to some small performance gains overall, nothing drastic
though.
Reviewers: hctim, morehouse, cferris, eugenis
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D70452
When we're not building libc's allocator, just use a regular TLS variable. This
lets the unit tests pass on Android devices whose libc uses Scudo. Otherwise
libc's copy of Scudo and the unit tests' copy will both try to use the same
TLS slot, in likely incompatible ways.
This requires using ELF TLS, so start passing -fno-emulated-tls when building
the library and the unit tests on Android.
Differential Revision: https://reviews.llvm.org/D70472
Summary:
`SCUDO_DEBUG` was not enabled for unit tests, meaning the `DCHECK`s
were never tripped. While turning this on, I discovered that a few
of those not-exercised checks were actually wrong. This CL addresses
those incorrect checks.
Not that to work in tests `CHECK_IMPL` has to explicitely use the
`scudo` namespace. Also changes a C cast to a C++ cast.
Reviewers: hctim, pcc, cferris, eugenis, vitalybuka
Subscribers: mgorny, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D70276
Summary: Bionic was modified to have all function names consistent. Modify the code and get rid of the special case for bionic since it's no longer needed.
Reviewers: cryptoad
Reviewed By: cryptoad
Subscribers: srhines, llvm-commits, #sanitizers
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D70031
Summary:
cferris@ found an issue due to the new Secondary free list behavior
and unfortunately it's completely my fault. The issue is twofold:
- I lost track of the (major) fact that the Combined assumes that
all chunks returned by the Secondary are zero'd out apprioriately
when dealing with `ZeroContents`. With the introduction of the
freelist, it's no longer the case as there can be a small portion
of memory between the header and the next page boundary that is
left untouched (the rest is zero'd via release). So the next time
that block is returned, it's not fully zero'd out.
- There was no test that would exercise that behavior :(
There are several ways to fix this, the one I chose makes the most
sense to me: we pass `ZeroContents` to the Secondary's `allocate`
and it zero's out the block if requested and it's coming from the
freelist. The prevents an extraneous `memset` in case the block
comes from `map`. Another possbility could have been to `memset`
in `deallocate`, but it's probably overzealous as all secondary
blocks don't need to be zero'd out.
Add a test that would have found the issue prior to fix.
Reviewers: morehouse, hctim, cferris, pcc, eugenis, vitalybuka
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D69675
Summary:
The secondary allocator is slow, because we map and unmap each block
on allocation and deallocation.
While I really like the security benefits of such a behavior, this
yields very disappointing performance numbers on Android for larger
allocation benchmarks.
So this change adds a free list to the secondary, that will hold
recently deallocated chunks, and (currently) release the extraneous
memory. This allows to save on some memory mapping operations on
allocation and deallocation. I do not think that this lowers the
security of the secondary, but can increase the memory footprint a
little bit (RSS & VA).
The maximum number of blocks the free list can hold is templatable,
`0U` meaning that we fallback to the old behavior. The higher that
number, the higher the extra memory footprint.
I added default configurations for all our platforms, but they are
likely to change in the near future based on needs and feedback.
Reviewers: hctim, morehouse, cferris, pcc, eugenis, vitalybuka
Subscribers: mgorny, #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D69570
Summary:
Apparently during the review of D69265, and my flailing around with
git, a somewhat important line disappeared.
On top of that, there was no test exercising that code path, and
while writing the follow up patch I intended to write, some `CHECK`s
were failing.
Re-add the missing line, and add a test that fails without said line.
Reviewers: hctim, morehouse, pcc, cferris
Reviewed By: hctim
Subscribers: #sanitizers, llvm-commits
Tags: #sanitizers, #llvm
Differential Revision: https://reviews.llvm.org/D69529
Christopher Ferris