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Our current reference leak checker uses finalizers to verify whether an object
has reached zero references before it is garbage collected. There are multiple
problems with this mechanism, so a rewrite is in order.
With finalizers, there is no way to guarantee that a finalizer will run before
the program exits. When an unreachable object with a finalizer is garbage
collected, its finalizer will be added to a queue and run asynchronously. The
best we can do is run garbage collection upon sandbox exit to make sure that
all finalizers are enqueued.
Furthermore, if there is a chain of finalized objects, e.g. A points to B
points to C, garbage collection needs to run multiple times before all of the
finalizers are enqueued. The first GC run will register the finalizer for A but
not free it. It takes another GC run to free A, at which point B's finalizer
can be registered. As a result, we need to run GC as many times as the length
of the longest such chain to have a somewhat reliable leak checker.
Finally, a cyclical chain of structs pointing to one another will never be
garbage collected if a finalizer is set. This is a well-known issue with Go
finalizers (https://github.com/golang/go/issues/7358). Using leak checking on
filesystem objects that produce cycles will not work and even result in memory
leaks.
The new leak checker stores reference counted objects in a global map when
leak check is enabled and removes them once they are destroyed. At sandbox
exit, any remaining objects in the map are considered as leaked. This provides
a deterministic way of detecting leaks without relying on the complexities of
finalizers and garbage collection.
This approach has several benefits over the former, including:
- Always detects leaks of objects that should be destroyed very close to
sandbox exit. The old checker very rarely detected these leaks, because it
relied on garbage collection to be run in a short window of time.
- Panics if we forgot to enable leak check on a ref-counted object (we will try
to remove it from the map when it is destroyed, but it will never have been
added).
- Can store extra logging information in the map values without adding to the
size of the ref count struct itself. With the size of just an int64, the ref
count object remains compact, meaning frequent operations like IncRef/DecRef
are more cache-efficient.
- Can aggregate leak results in a single report after the sandbox exits.
Instead of having warnings littered in the log, which were
non-deterministically triggered by garbage collection, we can print all
warning messages at once. Note that this could also be a limitation--the
sandbox must exit properly for leaks to be detected.
Some basic benchmarking indicates that this change does not significantly
affect performance when leak checking is enabled, which is understandable
since registering/unregistering is only done once for each filesystem object.
Updates #1486.
PiperOrigin-RevId: 338685972
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Reported-by: syzbot+c0e175d2b10708314eb3@syzkaller.appspotmail.com
PiperOrigin-RevId: 338386575
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Reported-by: syzbot+078580ce5dd6d607fcd8@syzkaller.appspotmail.com
Reported-by: syzbot+2096681f6891e7bf8aed@syzkaller.appspotmail.com
PiperOrigin-RevId: 337973519
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- Check the sticky bit in overlay.filesystem.UnlinkAt(). Fixes
StickyTest.StickyBitPermDenied.
- When configuring a VFS2 overlay in runsc, copy the lower layer's root
owner/group/mode to the upper layer's root (as in the VFS1 equivalent,
boot.addOverlay()). This makes the overlay root owned by UID/GID 65534 with
mode 0755 rather than owned by UID/GID 0 with mode 01777. Fixes
CreateTest.CreateFailsOnUnpermittedDir, which assumes that the test cannot
create files in /.
- MknodTest.UnimplementedTypesReturnError assumes that the creation of device
special files is not supported. However, while the VFS2 gofer client still
doesn't support device special files, VFS2 tmpfs does, and in the overlay
test dimension mknod() targets a tmpfs upper layer. The test initially has
all capabilities, including CAP_MKNOD, so its creation of these files
succeeds. Constrain these tests to VFS1.
- Rename overlay.nonDirectoryFD to overlay.regularFileFD and only use it for
regular files, using the original FD for pipes and device special files. This
is more consistent with Linux (which gets the original inode_operations, and
therefore file_operations, for these file types from ovl_fill_inode() =>
init_special_inode()) and fixes remaining mknod and pipe tests.
- Read/write 1KB at a time in PipeTest.Streaming, rather than 4 bytes. This
isn't strictly necessary, but it makes the test less obnoxiously slow on
ptrace.
Fixes #4407
PiperOrigin-RevId: 337971042
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PiperOrigin-RevId: 337919424
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All shm segments in an IPC namespace should be released once that namespace is
destroyed. Add reference counting to IPCNamespace so that once the last task
with a reference on it exits, we can trigger a destructor that will clean up
all shm segments that have not been explicitly freed by the application.
PiperOrigin-RevId: 337032977
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This fixes reference leaks related to accidentally forgetting to DecRef()
after calling one or the other.
PiperOrigin-RevId: 336918922
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PiperOrigin-RevId: 336822021
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PiperOrigin-RevId: 336694658
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- sysinfo(2) does not actually require a fine-grained breakdown of memory
usage. Accordingly, instead of calling pgalloc.MemoryFile.UpdateUsage() to
update the sentry's fine-grained memory accounting snapshot, just use
pgalloc.MemoryFile.TotalUsage() (which is a single fstat(), and therefore far
cheaper).
- Use the number of threads in the root PID namespace (i.e. globally) rather
than in the task's PID namespace for consistency with Linux (which just reads
global variable nr_threads), and add a new method to kernel.PIDNamespace to
allow this to be read directly from an underlying map rather than requiring
the allocation and population of an intermediate slice.
PiperOrigin-RevId: 336353100
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PiperOrigin-RevId: 335548610
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- When the KCOV_ENABLE_TRACE ioctl is called with the trace kind KCOV_TRACE_PC,
the kcov mode should be set to KCOV_*MODE*_TRACE_PC.
- When the owning task of kcov exits, the memory mapping should not be cleared
so it can be used by other tasks.
- Add more tests (also tested on native Linux kcov).
PiperOrigin-RevId: 335202585
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PiperOrigin-RevId: 335077195
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- Rewrite arch.Stack.{Push,Pop}. For the most part, stack now
implements marshal.CopyContext and can be used as the target of
marshal operations. Stack.Push had some extra logic for
automatically null-terminating slices. This was only used for two
specific types of slices, and is now handled explicitly.
- Delete usermem.CopyObject{In,Out}.
- Replace most remaining uses of the encoding/binary package with
go-marshal. Most of these were using the binary package to compute
the size of a struct, which go-marshal can directly replace. ~3 uses
of the binary package remain. These aren't reasonably replaceable by
go-marshal: for example one use is to construct the syscall
trampoline for systrap.
- Fill out remaining convenience wrappers in the primitive package.
PiperOrigin-RevId: 334502375
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PiperOrigin-RevId: 334428344
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Previously, we did not check the kcov mode when performing task work. As a
result, disabling kcov did not do anything.
Also avoid expensive atomic RMW when consuming coverage data. We don't need the
swap if the value is already zero (which is most of the time), and it is ok if
there are slight inconsistencies due to a race between coverage data generation
(incrementing the value) and consumption (reading a nonzero value and writing
zero).
PiperOrigin-RevId: 334049207
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Updates #1663
PiperOrigin-RevId: 333539293
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VFS2 socket record is not removed from the system-wide
socket table when the socket is released, which will lead
to a memory leak. This patch fixes this issue.
Fixes: #3874
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
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SocketEntry can be confusing with the template types as the 'Entry'
is usually used as a suffix for list element types, e.g. socketEntry
in the same package. Suggested by Dean (@dean-deng).
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
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Use HandleIOErrorVFS2 instead of custom error handling.
PiperOrigin-RevId: 333227581
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This change includes overlay, special regular gofer files, and hostfs.
Fixes #3589.
PiperOrigin-RevId: 332330860
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CopyContext is a better name for the interface because from
go-marshal's perspective, the interface has nothing to do with a
task. A kernel.Task happens to implement the interface, but so can
other things like MemoryManager and IO sequences.
PiperOrigin-RevId: 331959678
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PiperOrigin-RevId: 331940975
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OCI configuration includes support for specifying seccomp filters. In runc,
these filter configurations are converted into seccomp BPF programs and loaded
into the kernel via libseccomp. runsc needs to be a static binary so, for
runsc, we cannot rely on a C library and need to implement the functionality
in Go.
The generator added here implements basic support for taking OCI seccomp
configuration and converting it into a seccomp BPF program with the same
behavior as a program generated by libseccomp.
- New conditional operations were added to pkg/seccomp to support operations
available in OCI.
- AllowAny and AllowValue were renamed to MatchAny and EqualTo to better reflect
that syscalls matching the conditionals result in the provided action not
simply SCMP_RET_ALLOW.
- BuildProgram in pkg/seccomp no longer panics if provided an empty list of
rules. It now builds a program with the architecture sanity check only.
- ProgramBuilder now allows adding labels that are unused. However, backwards
jumps are still not permitted.
Fixes #510
PiperOrigin-RevId: 331938697
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This is needed for SO_LINGER, where close() is blocked for linger timeout and
we are holding the FDTable lock for the entire timeout which will not allow
us to create/delete other fds. We have to release the locks and then drop the
fds.
PiperOrigin-RevId: 331844185
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In Linux, FDSize is fs/proc/array.c:task_state() => struct fdtable::max_fds,
which is set to the underlying array's length in fs/file.c:alloc_fdtable().
Follow-up changes:
- Remove FDTable.GetRefs() and FDTable.GetRefsVFS2(), which are unused.
- Reset FDTable.used to 0 during restore, since the subsequent calls to
FDTable.setAll() increment it again, causing its value to be doubled. (After
this CL, FDTable.used is only used to avoid reallocation in FDTable.GetFDs(),
so this fix is not very visible.)
PiperOrigin-RevId: 331588190
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PiperOrigin-RevId: 331256608
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The args.MountNamespaceVFS2 is used again after the nil check,
instead, mntnsVFS2 which holds the expected reference should be
used. This patch fixes this issue.
Fixes: #3855
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
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PiperOrigin-RevId: 329572337
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Fixes *.sh Java runtime tests, where splice()-ing from a pipe to /dev/zero
would not actually empty the pipe.
There was no guarantee that the data would actually be consumed on a splice
operation unless the output file's implementation of Write/PWrite actually
called VFSPipeFD.CopyIn. Now, whatever bytes are "written" are consumed
regardless of whether CopyIn is called or not.
Furthermore, the number of bytes in the IOSequence for reads is now capped at
the amount of data actually available. Before, splicing to /dev/zero would
always return the requested splice size without taking the actual available
data into account.
This change also refactors the case where an input file is spliced into an
output pipe so that it follows a similar pattern, which is arguably cleaner
anyway.
Updates #3576.
PiperOrigin-RevId: 328843954
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PiperOrigin-RevId: 328839759
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This uses the refs_vfs2 template in vfs2 as well as objects common to vfs1 and
vfs2. Note that vfs1-only refcounts are not replaced, since vfs1 will be deleted
soon anyway.
The following structs now use the new tool, with leak check enabled:
devpts:rootInode
fuse:inode
kernfs:Dentry
kernfs:dir
kernfs:readonlyDir
kernfs:StaticDirectory
proc:fdDirInode
proc:fdInfoDirInode
proc:subtasksInode
proc:taskInode
proc:tasksInode
vfs:FileDescription
vfs:MountNamespace
vfs:Filesystem
sys:dir
kernel:FSContext
kernel:ProcessGroup
kernel:Session
shm:Shm
mm:aioMappable
mm:SpecialMappable
transport:queue
And the following use the template, but because they currently are not leak
checked, a TODO is left instead of enabling leak check in this patch:
kernel:FDTable
tun:tunEndpoint
Updates #1486.
PiperOrigin-RevId: 328460377
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In Linux, a kernel configuration is set that compiles the kernel with a
custom function that is called at the beginning of every basic block, which
updates the memory-mapped coverage information. The Go coverage tool does not
allow us to inject arbitrary instructions into basic blocks, but it does
provide data that we can convert to a kcov-like format and transfer them to
userspace through a memory mapping.
Note that this is not a strict implementation of kcov, which is especially
tricky to do because we do not have the same coverage tools available in Go
that that are available for the actual Linux kernel. In Linux, a kernel
configuration is set that compiles the kernel with a custom function that is
called at the beginning of every basic block to write program counters to the
kcov memory mapping. In Go, however, coverage tools only give us a count of
basic blocks as they are executed. Every time we return to userspace, we
collect the coverage information and write out PCs for each block that was
executed, providing userspace with the illusion that the kcov data is always
up to date. For convenience, we also generate a unique synthetic PC for each
block instead of using actual PCs. Finally, we do not provide thread-specific
coverage data (each kcov instance only contains PCs executed by the thread
owning it); instead, we will supply data for any file specified by --
instrumentation_filter.
Also, fix issue in nogo that was causing pkg/coverage:coverage_nogo
compilation to fail.
PiperOrigin-RevId: 328426526
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Some VFS operations (those which operate on FDs) get their credentials via the
context instead of via an explicit creds param. For these cases, we must pass
the overlay credentials on the context.
PiperOrigin-RevId: 327881259
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Our "Preconditions:" blocks are very useful to determine the input invariants,
but they are bit inconsistent throughout the codebase, which makes them harder
to read (particularly cases with 5+ conditions in a single paragraph).
I've reformatted all of the cases to fit in simple rules:
1. Cases with a single condition are placed on a single line.
2. Cases with multiple conditions are placed in a bulleted list.
This format has been added to the style guide.
I've also mentioned "Postconditions:", though those are much less frequently
used, and all uses already match this style.
PiperOrigin-RevId: 327687465
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This is needed to avoid circular dependencies between the vfs and kernel
packages.
PiperOrigin-RevId: 327355524
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The abstract socket namespace no longer holds any references on sockets.
Instead, TryIncRef() is used when a socket is being retrieved in
BoundEndpoint(). Abstract sockets are now responsible for removing themselves
from the namespace they are in, when they are destroyed.
Updates #1486.
PiperOrigin-RevId: 327064173
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It indicates that the Sentry has changed the state of the thread and
next calls of PullFullState() has to do nothing.
PiperOrigin-RevId: 325567415
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PiperOrigin-RevId: 324748508
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context is passed to DecRef() and Release() which is
needed for SO_LINGER implementation.
PiperOrigin-RevId: 324672584
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The subsequent systrap changes will need to import memmap from
the platform package.
PiperOrigin-RevId: 323409486
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Changes the API of tcpip.Clock to also provide a method for scheduling and
rescheduling work after a specified duration. This change also implements the
AfterFunc method for existing implementations of tcpip.Clock.
This is the groundwork required to mock time within tests. All references to
CancellableTimer has been replaced with the tcpip.Job interface, allowing for
custom implementations of scheduling work.
This is a BREAKING CHANGE for clients that implement their own tcpip.Clock or
use tcpip.CancellableTimer. Migration plan:
1. Add AfterFunc(d, f) to tcpip.Clock
2. Replace references of tcpip.CancellableTimer with tcpip.Job
3. Replace calls to tcpip.CancellableTimer#StopLocked with tcpip.Job#Cancel
4. Replace calls to tcpip.CancellableTimer#Reset with tcpip.Job#Schedule
5. Replace calls to tcpip.NewCancellableTimer with tcpip.NewJob.
PiperOrigin-RevId: 322906897
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PiperOrigin-RevId: 322904430
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Like task_work in Linux, this allows us to register callbacks to be executed
before returning to userspace. This is needed for kcov support, which requires
coverage information to be up-to-date whenever we are in user mode. We will
provide coverage data through the kcov interface to enable coverage-directed
fuzzing in syzkaller.
One difference from Linux is that task work cannot queue work before the
transition to userspace that it precedes; queued work will be picked up before
the next transition.
PiperOrigin-RevId: 322889984
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PiperOrigin-RevId: 321411758
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When --debug is enabled, the following log messages are
printed every second filling up the log:
D0430 18:04:42.823775 129561 parameters.go:238] Clock(Monotonic): error: 46 ns, adjusted frequency from 3591713733 Hz to 3591714196 Hz
D0430 18:04:42.823870 129561 parameters.go:238] Clock(Realtime): error: 36 ns, adjusted frequency from 3591714003 Hz to 3591714169 Hz
D0430 18:04:42.823892 129561 timekeeper.go:209] Updating VDSO parameters: {monotonicReady:1 monotonicBaseCycles:15758797714254696 monotonicBaseRef:29000233837 monotonicFrequency:3591714196 realtimeReady:1 realtimeBaseCycles:15758797714610880 realtimeBaseRef:1588269882823867374 realtimeFrequency:3591714169}
Info and warning messages for larger changes are kept the same.
PiperOrigin-RevId: 321048523
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This change gates all FUSE commands (by gating /dev/fuse) behind a runsc
flag. In order to use FUSE commands, use the --fuse flag with the --vfs2
flag. Check if FUSE is enabled by running dmesg in the sandbox.
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PiperOrigin-RevId: 319283715
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- Support FIOASYNC, FIO{SET,GET}OWN, SIOC{G,S}PGRP (refactor getting/setting
owner in the process).
- Unset signal recipient when setting owner with pid == 0 and
valid owner type.
Updates #2923.
PiperOrigin-RevId: 319231420
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Also make some fixes to vfs1's F_SETOWN. The fcntl test now entirely passes
on vfs2.
Fixes #2920.
PiperOrigin-RevId: 318669529
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