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2021-02-03[vfs] Make sticky bit check consistent with Linux.Ayush Ranjan
Our implementation of vfs.CheckDeleteSticky was not consistent with Linux, specifically not consistent with fs/linux.h:check_sticky(). One of the biggest differences was that the vfs implementation did not allow the owner of the sticky directory to delete files inside it that belonged to other users. This change makes our implementation consistent with Linux. Also adds an integration test to check for this. This bug is also present in VFS1. Updates #3027 PiperOrigin-RevId: 355557425
2021-01-20Move Lock/UnlockPOSIX into LockFD util.Dean Deng
PiperOrigin-RevId: 352904728
2021-01-14Check for existence before permissionsFabricio Voznika
Return EEXIST when overwritting a file as long as the caller has exec permission on the parent directory, even if the caller doesn't have write permission. Also reordered the mount write check, which happens before permission is checked. Closes #5164 PiperOrigin-RevId: 351868123
2020-12-04Overlay runsc regular file mounts with regular files.Jamie Liu
Fixes #4991 PiperOrigin-RevId: 345800333
2020-12-03Implement `fcntl` options `F_GETSIG` and `F_SETSIG`.Etienne Perot
These options allow overriding the signal that gets sent to the process when I/O operations are available on the file descriptor, rather than the default `SIGIO` signal. Doing so also populates `siginfo` to contain extra information about which file descriptor caused the event (`si_fd`) and what events happened on it (`si_band`). The logic around which FD is populated within `si_fd` matches Linux's, which means it has some weird edge cases where that value may not actually refer to a file descriptor that is still valid. This CL also ports extra S/R logic regarding async handler in VFS2. Without this, async I/O handlers aren't properly re-registered after S/R. PiperOrigin-RevId: 345436598
2020-11-12Filter dentries with non-zero refs in VFS2 gofer/overlay checks.Jamie Liu
PiperOrigin-RevId: 342161204
2020-11-09Initialize references with a value of 1.Dean Deng
This lets us avoid treating a value of 0 as one reference. All references using the refsvfs2 template must call InitRefs() before the reference is incremented/decremented, or else a panic will occur. Therefore, it should be pretty easy to identify missing InitRef calls during testing. Updates #1486. PiperOrigin-RevId: 341411151
2020-11-06[vfs] Return EEXIST when file already exists and rp.MustBeDir() is true.Ayush Ranjan
This is consistent with what Linux does. This was causing a PHP runtime test failure. Fixed it for VFS2. PiperOrigin-RevId: 341155209
2020-11-06[vfs] overlayfs: Do not unlink non-existing whiteout during file creation.Ayush Ranjan
We can reuse information about whether a whiteout exists on a given file path from stepLocked when creating a file at that path. This helps save an Unlink call to the upper filesystem if the whiteout does NOT exist (common case). Plumbs this information from lookupLocked() -> getChildLocked() -> stepLocked(). This also helped save a Lookup in RenameAt(). Fixes #1199 PiperOrigin-RevId: 341105351
2020-10-28Add logging option to leak checker.Dean Deng
Also refactor the template and CheckedObject interface to make this cleaner. Updates #1486. PiperOrigin-RevId: 339577120
2020-10-28Invalidate overlay.dentry.dirents during open() file creation.Jamie Liu
Updates #1199 PiperOrigin-RevId: 339528827
2020-10-27Assign VFS2 overlay device numbers based on layer device numbers.Jamie Liu
In VFS1's overlayfs, files use the device and inode number of the lower layer inode if one exists, and the upper layer inode otherwise. The former behavior is inefficient (requiring lower layer lookups even if the file exists and is otherwise wholly determined by the upper layer), and somewhat dangerous if the lower layer is also observable (since both the overlay and lower layer file will have the same device and inode numbers and thus appear to be the same file, despite being behaviorally different). VFS2 overlayfs imitates Linux overlayfs (in its default configuration) instead; it always uses the inode number from the originating layer, but synthesizes a unique device number for directories and another device number for non-directory files that have not been copied-up. As it turns out, the latter is insufficient (in VFS2, and possibly Linux as well), because a given layer may include files with different device numbers. If two distinct files on such a layer have device number X and Y respectively, but share inode number Z, then the overlay will map both files to some private device number X' and inode number Z, potentially confusing applications. Fix this by assigning synthetic device numbers based on the lower layer's device number, rather than the lower layer's vfs.Filesystem. PiperOrigin-RevId: 339300341
2020-10-24Add leak checking to vfs2 structures that cannot use the refs_vfs2 template.Dean Deng
Updates #1486. PiperOrigin-RevId: 338832085
2020-10-23Support VFS2 save/restore.Jamie Liu
Inode number consistency checks are now skipped in save/restore tests for reasons described in greatest detail in StatTest.StateDoesntChangeAfterRename. They pass in VFS1 due to the bug described in new test case SimpleStatTest.DifferentFilesHaveDifferentDeviceInodeNumberPairs. Fixes #1663 PiperOrigin-RevId: 338776148
2020-10-19Fix runsc tests on VFS2 overlay.Jamie Liu
- 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
2020-10-13[vfs2] Add FilesystemType.Release to avoid reference leaks.Dean Deng
Singleton filesystem like devpts and devtmpfs have a single filesystem shared among all mounts, so they acquire a "self-reference" when initialized that must be released when the entire virtual filesystem is released at sandbox exit. PiperOrigin-RevId: 336828852
2020-09-28Support inotify in overlayfs.Dean Deng
Fixes #1479, #317. PiperOrigin-RevId: 334258052
2020-09-24Add basic stateify annotations.Adin Scannell
Updates #1663 PiperOrigin-RevId: 333539293
2020-09-18Implement fsimpl/overlay.filesystem.RenameAt.Jamie Liu
Updates #1199 PiperOrigin-RevId: 332539197
2020-09-17Complete vfs2 implementation of fallocate.Dean Deng
This change includes overlay, special regular gofer files, and hostfs. Fixes #3589. PiperOrigin-RevId: 332330860
2020-09-11Implement copy-up-coherent mmap for VFS2 overlayfs.Jamie Liu
This is very similar to copy-up-coherent mmap in the VFS1 overlay, with the minor wrinkle that there is no fs.InodeOperations.Mappable(). Updates #1199 PiperOrigin-RevId: 331206314
2020-09-08[vfs] overlayfs: decref VD when not using it.Ayush Ranjan
overlay/filesystem.go:lookupLocked() did not DecRef the VD on some error paths when it would not end up saving or using the VD. PiperOrigin-RevId: 330589742
2020-09-08[vfs] Capitalize x in the {Get/Set/Remove/List}xattr functions.Ayush Ranjan
PiperOrigin-RevId: 330554450
2020-09-02[vfs] Implement xattr for overlayfs.Ayush Ranjan
PiperOrigin-RevId: 329825497
2020-09-02[vfs] Fix error handling in overlayfs OpenAt.Ayush Ranjan
Updates #1199 PiperOrigin-RevId: 329802274
2020-08-26Remove spurious fd.IncRef().Nicolas Lacasse
PiperOrigin-RevId: 328583461
2020-08-26tmpfs: Allow xattrs in the trusted namespace if creds has CAP_SYS_ADMIN.Nicolas Lacasse
This is needed to support the overlay opaque attribute. PiperOrigin-RevId: 328552985
2020-08-25overlay: clonePrivateMount must pass a Dentry reference to MakeVirtualDentry.Nicolas Lacasse
PiperOrigin-RevId: 328410065
2020-08-21Pass overlay credentials via context in copy up.Nicolas Lacasse
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
2020-08-20Consistent precondition formattingMichael Pratt
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
2020-08-18Avoid holding locks when opening files in VFS2.Jamie Liu
Fixes #3243, #3521 PiperOrigin-RevId: 327308890
2020-08-07[vfs2] Fix tmpfs mounting.Ayush Ranjan
Earlier we were using NLink to decide if /tmp is empty or not. However, NLink at best tells us about the number of subdirectories (via the ".." entries). NLink = n + 2 for n subdirectories. But it does not tell us if the directory is empty. There still might be non-directory files. We could also not rely on NLink because host overlayfs always returned 1. VFS1 uses Readdir to decide if the directory is empty. Used a similar approach. We now use IterDirents to decide if the "/tmp" directory is empty. Fixes #3369 PiperOrigin-RevId: 325554234
2020-08-03Plumbing context.Context to DecRef() and Release().Nayana Bidari
context is passed to DecRef() and Release() which is needed for SO_LINGER implementation. PiperOrigin-RevId: 324672584
2020-07-23Add permission checks to vfs2 truncate.Dean Deng
- Check write permission on truncate(2). Unlike ftruncate(2), truncate(2) fails if the user does not have write permissions on the file. - For gofers under InteropModeShared, check file type before making a truncate request. We should fail early and avoid making an rpc when possible. Furthermore, depending on the remote host's failure may give us unexpected behavior--if the host converts the truncate request to an ftruncate syscall on an open fd, we will get EINVAL instead of EISDIR. Updates #2923. PiperOrigin-RevId: 322913569
2020-07-23FileDescription is hard to spell.Dean Deng
Fix typos. PiperOrigin-RevId: 322913282
2020-06-23Support inotify in vfs2 gofer fs.Dean Deng
Because there is no inode structure stored in the sandbox, inotify watches must be held on the dentry. This would be an issue in the presence of hard links, where multiple dentries would need to share the same set of watches, but in VFS2, we do not support the internal creation of hard links on gofer fs. As a result, we make the assumption that every dentry corresponds to a unique inode. Furthermore, dentries can be cached and then evicted, even if the underlying file has not be deleted. We must prevent this from occurring if there are any watches that would be lost. Note that if the dentry was deleted or invalidated (d.vfsd.IsDead()), we should still destroy it along with its watches. Additionally, when a dentry’s last watch is removed, we cache it if it also has zero references. This way, the dentry can eventually be evicted from memory if it is no longer needed. This is accomplished with a new dentry method, OnZeroWatches(), which is called by Inotify.RmWatch and Inotify.Release. Note that it must be called after all inotify locks are released to avoid violating lock order. Stress tests are added to make sure that inotify operations don't deadlock with gofer.OnZeroWatches. Updates #1479. PiperOrigin-RevId: 317958034
2020-06-17Implement Sync() to directoriesFabricio Voznika
Updates #1035, #1199 PiperOrigin-RevId: 317028108
2020-06-17Implement POSIX locksFabricio Voznika
- 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
2020-06-11Add //pkg/sentry/fsimpl/overlay.Jamie Liu
Major differences from existing overlay filesystems: - Linux allows lower layers in an overlay to require revalidation, but not the upper layer. VFS1 allows the upper layer in an overlay to require revalidation, but not the lower layer. VFS2 does not allow any layers to require revalidation. (Now that vfs.MkdirOptions.ForSyntheticMountpoint exists, no uses of overlay in VFS1 are believed to require upper layer revalidation; in particular, the requirement that the upper layer support the creation of "trusted." extended attributes for whiteouts effectively required the upper filesystem to be tmpfs in most cases.) - Like VFS1, but unlike Linux, VFS2 overlay does not attempt to make mutations of the upper layer atomic using a working directory and features like RENAME_WHITEOUT. (This may change in the future, since not having a working directory makes error recovery for some operations, e.g. rmdir, particularly painful.) - Like Linux, but unlike VFS1, VFS2 represents whiteouts using character devices with rdev == 0; the equivalent of the whiteout attribute on directories is xattr trusted.overlay.opaque = "y"; and there is no equivalent to the whiteout attribute on non-directories since non-directories are never merged with lower layers. - Device and inode numbers work as follows: - In Linux, modulo the xino feature and a special case for when all layers are the same filesystem: - Directories use the overlay filesystem's device number and an ephemeral inode number assigned by the overlay. - Non-directories that have been copied up use the device and inode number assigned by the upper filesystem. - Non-directories that have not been copied up use a per-(overlay, layer)-pair device number and the inode number assigned by the lower filesystem. - In VFS1, device and inode numbers always come from the lower layer unless "whited out"; this has the adverse effect of requiring interaction with the lower filesystem even for non-directory files that exist on the upper layer. - In VFS2, device and inode numbers are assigned as in Linux, except that xino and the samefs special case are not supported. - Like Linux, but unlike VFS1, VFS2 does not attempt to maintain memory mapping coherence across copy-up. (This may have to change in the future, as users may be dependent on this property.) - Like Linux, but unlike VFS1, VFS2 uses the overlayfs mounter's credentials when interacting with the overlay's layers, rather than the caller's. - Like Linux, but unlike VFS1, VFS2 permits multiple lower layers in an overlay. - Like Linux, but unlike VFS1, VFS2's overlay filesystem is application-mountable. Updates #1199 PiperOrigin-RevId: 316019067
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