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PiperOrigin-RevId: 347047550
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We would like to track locks ordering to detect ordering violations. Detecting
violations is much simpler if mutexes must be unlocked by the same goroutine
that locked them.
Thus, as a first step to tracking lock ordering, add this lock/unlock
requirement to gVisor's sync.Mutex. This is more strict than the Go standard
library's sync.Mutex, but initial testing indicates only a single lock that is
used across goroutines. The new sync.CrossGoroutineMutex relaxes the
requirement (but will not provide lock order checking).
Due to the additional overhead, enforcement is only enabled with the
"checklocks" build tag. Build with this tag using:
bazel build --define=gotags=checklocks ...
From my spot-checking, this has no changed inlining properties when disabled.
Updates #4804
PiperOrigin-RevId: 343370200
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PiperOrigin-RevId: 343196927
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The default pipe size already matched linux, and is unchanged.
Furthermore `atomicIOBytes` is made a proper constant (as it is in Linux). We
were plumbing usermem.PageSize everywhere, so this is no functional change.
PiperOrigin-RevId: 340497006
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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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When the file closes, it attempts to write dirty cached
attributes to the file. This should not be done when the
mount is readonly.
PiperOrigin-RevId: 315585058
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Linux 4.18 and later make reads and writes coherent between pre-copy-up and
post-copy-up FDs representing the same file on an overlay filesystem. However,
memory mappings remain incoherent:
- Documentation/filesystems/overlayfs.rst, "Non-standard behavior": "If a file
residing on a lower layer is opened for read-only and then memory mapped with
MAP_SHARED, then subsequent changes to the file are not reflected in the
memory mapping."
- fs/overlay/file.c:ovl_mmap() passes through to the underlying FD without any
management of coherence in the overlay.
- Experimentally on Linux 5.2:
```
$ cat mmap_cat_page.c
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
int main(int argc, char **argv) {
if (argc < 2) {
errx(1, "syntax: %s [FILE]", argv[0]);
}
const int fd = open(argv[1], O_RDONLY);
if (fd < 0) {
err(1, "open(%s)", argv[1]);
}
const size_t page_size = sysconf(_SC_PAGE_SIZE);
void* page = mmap(NULL, page_size, PROT_READ, MAP_SHARED, fd, 0);
if (page == MAP_FAILED) {
err(1, "mmap");
}
for (;;) {
write(1, page, strnlen(page, page_size));
if (getc(stdin) == EOF) {
break;
}
}
return 0;
}
$ gcc -O2 -o mmap_cat_page mmap_cat_page.c
$ mkdir lowerdir upperdir workdir overlaydir
$ echo old > lowerdir/file
$ sudo mount -t overlay -o "lowerdir=lowerdir,upperdir=upperdir,workdir=workdir" none overlaydir
$ ./mmap_cat_page overlaydir/file
old
^Z
[1]+ Stopped ./mmap_cat_page overlaydir/file
$ echo new > overlaydir/file
$ cat overlaydir/file
new
$ fg
./mmap_cat_page overlaydir/file
old
```
Therefore, while the VFS1 gofer client's behavior of reopening read FDs is only
necessary pre-4.18, replacing existing memory mappings (in both sentry and
application address spaces) with mappings of the new FD is required regardless
of kernel version, and this latter behavior is common to both VFS1 and VFS2.
Re-document accordingly, and change the runsc flag to enabled by default.
New test:
- Before this CL: https://source.cloud.google.com/results/invocations/5b222d2c-e918-4bae-afc4-407f5bac509b
- After this CL: https://source.cloud.google.com/results/invocations/f28c747e-d89c-4d8c-a461-602b33e71aab
PiperOrigin-RevId: 311361267
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Fixes #2651.
PiperOrigin-RevId: 311193661
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Synthetic sockets do not have the race condition issue in VFS2, and we will
get rid of privateunixsocket as well.
Fixes #1200.
PiperOrigin-RevId: 310386474
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p9.NoUID/GID (== uint32(-1) == auth.NoID) is not a valid auth.KUID/KGID; in
particular, using it for file ownership causes capabilities to be ineffective
since file capabilities require that the file's KUID and KGID are mapped into
the capability holder's user namespace [1], and auth.NoID is not mapped into
any user namespace. Map p9.NoUID/GID to a different, valid KUID/KGID; in the
unlikely case that an application actually using the overflow KUID/KGID
attempts an operation that is consequently permitted by client permission
checks, the remote operation will still fail with EPERM.
Since this changes the VFS2 gofer client to no longer ignore the invalid IDs
entirely, this CL both permits and requires that we change synthetic mount point
creation to use root credentials.
[1] See fs.Inode.CheckCapability or vfs.GenericCheckPermissions.
PiperOrigin-RevId: 309856455
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Named pipes and sockets can be represented in two ways in gofer fs:
1. As a file on the remote filesystem. In this case, all file operations are
passed through 9p.
2. As a synthetic file that is internal to the sandbox. In this case, the
dentry stores an endpoint or VFSPipe for sockets and pipes respectively,
which replaces interactions with the remote fs through the gofer.
In gofer.filesystem.MknodAt, we attempt to call mknod(2) through 9p,
and if it fails, fall back to the synthetic version.
Updates #1200.
PiperOrigin-RevId: 308828161
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Sentry metrics with nanoseconds units are labeled as such, and non-cumulative
sentry metrics are supported.
PiperOrigin-RevId: 307621080
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The comments in the ticket indicate that this behavior
is fine and that the ticket should be closed, so we shouldn't
need pointers to the ticket.
PiperOrigin-RevId: 306266071
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The sentry doesn't allow execve, but it's a good defense
in-depth measure.
PiperOrigin-RevId: 305958737
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PiperOrigin-RevId: 305588941
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Determine system time from within the sentry rather than relying on the remote
filesystem to prevent inconsistencies.
Resolve related TODOs; the time discrepancies in question don't exist anymore.
PiperOrigin-RevId: 305557099
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PiperOrigin-RevId: 294295852
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Note that these are only implemented for tmpfs, and other impls will still
return EOPNOTSUPP.
PiperOrigin-RevId: 293899385
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Internal pipes are supported similarly to how internal UDS is done.
It is also controlled by the same flag.
Fixes #1102
PiperOrigin-RevId: 293150045
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Because the abi will depend on the core types for marshalling (usermem,
context, safemem, safecopy), these need to be flattened from the sentry
directory. These packages contain no sentry-specific details.
PiperOrigin-RevId: 291811289
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PiperOrigin-RevId: 291745021
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There was a very bare get/setxattr in the InodeOperations interface. Add
context.Context to both, size to getxattr, and flags to setxattr.
Note that extended attributes are passed around as strings in this
implementation, so size is automatically encoded into the value. Size is
added in getxattr so that implementations can return ERANGE if a value is larger
than can fit in the user-allocated buffer. This prevents us from unnecessarily
passing around an arbitrarily large xattr when the user buffer is actually too
small.
Don't use the existing xattrwalk and xattrcreate messages and define our
own, mainly for the sake of simplicity.
Extended attributes will be implemented in future commits.
PiperOrigin-RevId: 290121300
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* Rename syncutil to sync.
* Add aliases to sync types.
* Replace existing usage of standard library sync package.
This will make it easier to swap out synchronization primitives. For example,
this will allow us to use primitives from github.com/sasha-s/go-deadlock to
check for lock ordering violations.
Updates #1472
PiperOrigin-RevId: 289033387
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