If libnccl.so.2:getHostHash() fails to fopen(/proc/sys/kernel/random/boot_id),
it calls fclose(NULL) and takes SIGSEGV.
Updates #9827
PiperOrigin-RevId: 592899854
This change introduces the nsfs file system. Each new namespace allocates
a new nsfs inode.
Here are reasons why we need these inodes:
* each namespace has to have an unique id.
* proc/pid/ns/ contains one entry for each namespace. Bind mounting one of
the files in this directory to somewhere else in the filesystem keeps the
corresponding namespace alive even if all processes currently in
the namespace terminate.
* setns() allows the calling process to join an existing namespace specified
by a file descriptor.
PiperOrigin-RevId: 550694515
Since refsvfs2 are used in netstack, we should use atomicbitops to avoid
breaking 32-bit builds.
On 64-bit builds there is no performance difference.
PiperOrigin-RevId: 439687980
Removes package syserror and moves still relevant code to either linuxerr
or to syserr (to be later removed).
Internal errors are converted from random types to *errors.Error types used
in linuxerr. Internal errors are in linuxerr/internal.go.
PiperOrigin-RevId: 390724202
Add Equals method to compare syserror and unix.Errno errors to linuxerr errors.
This will facilitate removal of syserror definitions in a followup, and
finding needed conversions from unix.Errno to linuxerr.
PiperOrigin-RevId: 380909667
Split usermem package to help remove syserror dependency in go_marshal.
New hostarch package contains code not dependent on syserror.
PiperOrigin-RevId: 365651233
Restrict ptrace(2) according to the default configurations of the YAMA security
module (mode 1), which is a common default among various Linux distributions.
The new access checks only permit the tracer to proceed if one of the following
conditions is met:
a) The tracer is already attached to the tracee.
b) The target is a descendant of the tracer.
c) The target has explicitly given permission to the tracer through the
PR_SET_PTRACER prctl.
d) The tracer has CAP_SYS_PTRACE.
See security/yama/yama_lsm.c for more details.
Note that these checks are added to CanTrace, which is checked for
PTRACE_ATTACH as well as some other operations, e.g., checking a process'
memory layout through /proc/[pid]/mem.
Since this patch adds restrictions to ptrace, it may break compatibility for
applications run by non-root users that, for instance, rely on being able to
trace processes that are not descended from the tracer (e.g., `gdb -p`). YAMA
restrictions can be turned off by setting /proc/sys/kernel/yama/ptrace_scope
to 0, or exceptions can be made on a per-process basis with the PR_SET_PTRACER
prctl.
Reported-by: syzbot+622822d8bca08c99e8c8@syzkaller.appspotmail.com
PiperOrigin-RevId: 359237723
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
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
- Change FileDescriptionImpl Lock/UnlockPOSIX signature to
take {start,length,whence}, so the correct offset can be
calculated in the implementations.
- Create PosixLocker interface to make it possible to share
the same locking code from different implementations.
Closes#1480
PiperOrigin-RevId: 316910286
LockFD is the generic implementation that can be embedded in
FileDescriptionImpl implementations. Unique lock ID is
maintained in vfs.FileDescription and is created on demand.
Updates #1480
PiperOrigin-RevId: 315604825
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