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2021-02-05[vfs] Handle `.` and `..` as last path component names in kernfs Rename.Ayush Ranjan
According to vfs.FilesystemImpl.RenameAt documentation: - If the last path component in rp is "." or "..", and opts.Flags contains RENAME_NOREPLACE, RenameAt returns EEXIST. - If the last path component in rp is "." or "..", and opts.Flags does not contain RENAME_NOREPLACE, RenameAt returns EBUSY. Reported-by: syzbot+6189786e64fe13fe43f8@syzkaller.appspotmail.com PiperOrigin-RevId: 355959266
2021-02-04Call kernfs.syntheticDir.InitRefs() on creation.Nicolas Lacasse
PiperOrigin-RevId: 355675900
2021-01-28[vfs] Fix rename implementation in OrderedChildren.Ayush Ranjan
Fixes #3027 as there is just 1 writable user using OrderedChildren's rename, unlink and rmdir (kernfs.syntheticDirectory) but it doesn't support the sticky bit yet. Fuse which is the other writable user implements its own Inode operations. PiperOrigin-RevId: 354386522
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
2020-11-18[vfs] kernfs: Do not panic if destroyed dentry is cached.Ayush Ranjan
If a kernfs user does not cache dentries, then cacheLocked will destroy the dentry. The current DecRef implementation will be racy in this case as the following can happen: - Goroutine 1 calls DecRef and decreases ref count from 1 to 0. - Goroutine 2 acquires d.fs.mu for reading and calls IncRef and increasing the ref count from 0 to 1. - Goroutine 2 releases d.fs.mu and calls DecRef again decreasing ref count from 1 to 0. - Goroutine 1 now acquires d.fs.mu and calls cacheLocked which destroys the dentry. - Goroutine 2 now acquires d.fs.mu and calls cacheLocked to find that the dentry is already destroyed! Earlier we would panic in this case, we could instead just return instead of adding complexity to handle this race. This is similar to what the gofer client does. We do not want to lock d.fs.mu in the case that the filesystem caches dentries (common case as procfs and sysfs do this) to prevent congestion due to lock contention. PiperOrigin-RevId: 343229496
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
2020-11-06Avoid extra DecRef on kernfs root for "kept" dentries.Dean Deng
The root dentry was not created through Inode.Lookup, so we should not release a reference even if inode.Keep() is true. PiperOrigin-RevId: 341103220
2020-11-02[vfs2] Refactor kernfs checkCreateLocked.Dean Deng
Don't return the filename, since it can already be determined by the caller. This was causing a panic in RenameAt, which relied on the name to be nonempty even if the error was EEXIST. Reported-by: syzbot+e9f117d000301e42361f@syzkaller.appspotmail.com PiperOrigin-RevId: 340381946
2020-10-30Adjust error handling in kernfs rename.Dean Deng
Read-only directories (e.g. under /sys, /proc) should return EPERM for rename. PiperOrigin-RevId: 339979022
2020-10-30Fix rename error handling for VFS2 kernfs.Dean Deng
The non-errno error was causing panics before. PiperOrigin-RevId: 339969348
2020-10-28Add leak checking for kernfs.Dentry.Dean Deng
Updates #1486. PiperOrigin-RevId: 339581879
2020-10-28[vfs] Refactor hostfs mmap into kernfs util.Ayush Ranjan
PiperOrigin-RevId: 339505487
2020-10-26[vfs] kernfs: Implement LRU cache for kernfs dentries.Ayush Ranjan
Much like the VFS2 gofer client, kernfs too now caches dentries. The size of the LRU cache is configurable via mount options. Have adopted the same reference semantics from gofer client dentry. Only sysfs and procfs use this LRU cache. The rest of the kernfs users (devpts, fusefs, host, pipefs, sockfs) still use the no cache approach. PiperOrigin-RevId: 339139835
2020-10-23[vfs] kernfs: cleanup/refactor.Ayush Ranjan
PiperOrigin-RevId: 338728070
2020-10-23[vfs] kernfs: Implement remaining InodeAttr fields.Ayush Ranjan
Added the following fields in kernfs.InodeAttr: - blockSize - atime - mtime - ctime Also resolved all TODOs for #1193. Fixes #1193 PiperOrigin-RevId: 338714527
2020-10-23Rewrite reference leak checker without finalizers.Dean Deng
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
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
2020-10-12[vfs] kernfs: Fix inode memory leak issue.Ayush Ranjan
This change aims to fix the memory leak issue reported in #3933. Background: VFS2 kernfs kept accumulating invalid dentries if those dentries were not walked on. After substantial consideration of the problem by our team, we decided to have an LRU cache solution. This change is the first part to that solution, where we don't cache anything. The LRU cache can be added on top of this. What has changed: - Introduced the concept of an inode tree in kernfs.OrderedChildren. This is helpful is cases where the lifecycle of an inode is different from that of a dentry. - OrderedChildren now deals with initialized inodes instead of initialized dentries. It now implements Lookup() where it constructs a new dentry using the inode. - OrderedChildren holds a ref on all its children inodes. With this change, now an inode can "outlive" a dentry pointing to it. See comments in kernfs.OrderedChildren. - The kernfs dentry tree is solely maintained by kernfs only. Inode implementations can not modify the dentry tree. - Dentries that reach ref count 0 are removed from the dentry tree. - revalidateChildLocked now defer-DecRefs the newly created dentry from Inode.Lookup(), limiting its life to the current filesystem operation. If refs are picked on the dentry during the FS op (via an FD or something), then it will stick around and will be removed when the FD is closed. So there is essentially _no caching_ for Look()ed up dentries. - kernfs.DecRef does not have the precondition that fs.mu must be locked. Fixes #3933 PiperOrigin-RevId: 336768576
2020-09-27Fix kernfs race condition.Dean Deng
Do not release dirMu between checking whether to create a child and actually inserting it. Also fixes a bug in fusefs which was causing it to deadlock under the new lock ordering. We do not need to call kernfs.Dentry.InsertChild from newEntry because it will always be called at the kernfs filesystem layer. Updates #1193. PiperOrigin-RevId: 334049264
2020-09-24[vfs] kernfs: Do not hold reference on the inode when opening FD.Ayush Ranjan
The FD should hold a reference on the dentry they were opened on which in turn holds a reference on the inode it points to. PiperOrigin-RevId: 333589223
2020-09-24[vfs] [2/2] kernfs: kernfs: Internally use kernfs.Dentry instead of vfs.Dentry.Ayush Ranjan
Update signatures for: - All methods in inodeDirectory - deferDecRef() and Filesystem.droppedDentries - newSyntheticDirectory() - `slot`s used in OrderedChildren and subsequent methods like replaceChildLocked() and checkExistingLocked() - stepExistingLocked(), walkParentDirLocked(), checkCreateLocked() Updates #1193 PiperOrigin-RevId: 333558866
2020-09-24Add basic stateify annotations.Adin Scannell
Updates #1663 PiperOrigin-RevId: 333539293
2020-09-23[vfs] kernfs: Enable leak checking consistently.Ayush Ranjan
There were some instances where we were not enabling leak checking. PiperOrigin-RevId: 333418571
2020-09-22[vfs] [1/2] kernfs: Internally use kernfs.Dentry instead of vfs.Dentry.Ayush Ranjan
Update signatures for: - walkExistingLocked - checkDeleteLocked - Inode.Open Updates #1193 PiperOrigin-RevId: 333163381
2020-09-21Use kernfs.Dentry for kernfs.Lookup.Dean Deng
Updates #1193. PiperOrigin-RevId: 332939026
2020-09-18Merge pull request #3972 from btw616:fix/commentsgVisor bot
PiperOrigin-RevId: 332486111
2020-09-17Fix kernfs unlinkat and rmdirat incorrect resolved path nameJinmou Li
2020-09-17fsimpl: improve the "implements" commentsTiwei Bie
As noticed by @ayushr2, the "implements" comments are not consistent, e.g. // IterDirents implements kernfs.inodeDynamicLookup. // Generate implements vfs.DynamicBytesSource.Generate. This patch improves this by making the comments like this consistently include the package name (when the interface and struct are not in the same package) and method name. Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
2020-09-16Implement FUSE_UNLINKBoyuan He
Fixes #3696
2020-09-16Implement FUSE_SETATTRCraig Chi
This commit implements FUSE_SETATTR command. When a system call modifies the metadata of a regular file or a folder by chown(2), chmod(2), truncate(2), utime(2), or utimes(2), they should be translated to corresponding FUSE_SETATTR command and sent to the FUSE server. Fixes #3332
2020-09-16fuse: Implement IterDirents for directory file descriptionRidwan Sharif
Fixes #3255. This change adds support for IterDirents. You can now use `ls` in the FUSE sandbox. Co-authored-by: Craig Chi <craigchi@google.com>
2020-09-16Implement FUSE_RMDIRRidwan Sharif
Fixes #3587 Co-authored-by: Craig Chi <craigchi@google.com>
2020-09-16Implement FUSE_READLINKBoyuan He
Fixes #3316
2020-09-16Implement FUSE_LOOKUPAndrei Vagin
Fixes #3231 Co-authored-by: Boyuan He <heboyuan@google.com>
2020-09-15Support setting STATX_SIZE for kernfs.InodeAttrs.Dean Deng
Make setting STATX_SIZE a no-op, if it is valid for the given permissions and file type. Also update proc tests, which were overfitted before. Fixes #3842. Updates #1193. PiperOrigin-RevId: 331861087
2020-09-08Implement synthetic mountpoints for kernfs.Jamie Liu
PiperOrigin-RevId: 330629897
2020-09-08Honor readonly flag for root mountFabricio Voznika
Updates #1487 PiperOrigin-RevId: 330580699
2020-09-08[vfs] Capitalize x in the {Get/Set/Remove/List}xattr functions.Ayush Ranjan
PiperOrigin-RevId: 330554450
2020-08-28Implement StatFS for various VFS2 filesystems.Rahat Mahmood
This mainly involved enabling kernfs' client filesystems to provide a StatFS implementation. Fixes #3411, #3515. PiperOrigin-RevId: 329009864
2020-08-25Use new reference count utility throughout gvisor.Dean Deng
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
2020-08-21Clarify seek behaviour for kernfs.GenericDirectoryFD.Rahat Mahmood
- Remove comment about GenericDirectoryFD not being compatible with dynamic directories. It is currently being used to implement dynamic directories. - Try to handle SEEK_END better than setting the offset to infinity. SEEK_END is poorly defined for dynamic directories anyways, so at least try make it work correctly for the static entries. Updates #1193. PiperOrigin-RevId: 327890128
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
2020-08-18Get rid of kernfs.Inode.Destroy.Dean Deng
This interface method is unneeded. PiperOrigin-RevId: 327370325
2020-08-18Avoid holding locks when opening files in VFS2.Jamie Liu
Fixes #3243, #3521 PiperOrigin-RevId: 327308890
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
2020-07-14Include context in kernfs.Inode.Stat methodCraig Chi
To implement stat(2) in FUSE, we have to embed credentials and pid in request header. The information should be extracted from the context passed to VFS layer. Therefore `Stat()` signature in `kernfs.Inode` interface should include context as first argument. Some other fs implementations need to be modified as well, such as devpts, host, pipefs, and proc. Fixes #3235
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