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kernel: release FDTable lock before calling file methods

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This change breaks dependency of FDTable.mu and kernfs.filesystemRWMutex.

panic: WARNING: circular locking detected: kernel.taskMutex -> kernel.fdTableMutex:

gvisor.dev/gvisor/pkg/sentry/kernel.(*fdTableMutex).Lock(0xc00491a110)
        bazel-out/k8-fastbuild-ST-1a50d7a562c6/bin/pkg/sentry/kernel/fd_table_mutex.go:16 +0x34
gvisor.dev/gvisor/pkg/sentry/kernel.(*FDTable).Fork(0xc00491a100, {0x158ef70, 0xc005fdb500}, 0x2073b60)
        pkg/sentry/kernel/fd_table.go:637 +0xca
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Unshare(0xc005fdb500, 0x4040400)
        pkg/sentry/kernel/task_clone.go:483 +0x72d

known lock chain: kernel.fdTableMutex -> kernfs.filesystemRWMutex -> kernel.taskSetRWMutex -> kernel.signalHandlersMutex -> kernel.taskMutex

gvisor.dev/gvisor/pkg/sentry/kernel.(*FDTable).String(0xc000cd36c0)
        pkg/sentry/kernel/fd_table.go:245 +0x139

====== kernfs.filesystemRWMutex -> kernel.taskSetRWMutex =====
gvisor.dev/gvisor/pkg/sentry/kernel.(*PIDNamespace).IDOfThreadGroup(0xc00019ce40, 0xc0004a2800)
        pkg/sentry/kernel/threads.go:264 +0x35
gvisor.dev/gvisor/pkg/sentry/fsimpl/proc.(*selfSymlink).Readlink(0xc000074460, {0x158ef70, 0xc00027e000}, 0xc0003ba510)
        pkg/sentry/fsimpl/proc/tasks_files.go:58 +0x6d
gvisor.dev/gvisor/pkg/sentry/fsimpl/proc.(*selfSymlink).Getlink(0xc0004b5500, {0x158ef70, 0xc00027e000}, 0x4)
        pkg/sentry/fsimpl/proc/tasks_files.go:66 +0x2d

====== kernel.taskSetRWMutex -> kernel.signalHandlersMutex =====
gvisor.dev/gvisor/pkg/sentry/kernel.(*TaskSet).newTask(0xc00019cea0, 0xc0004f1570)
        pkg/sentry/kernel/task_start.go:177 +0x656
gvisor.dev/gvisor/pkg/sentry/kernel.(*TaskSet).NewTask(0xc00014f180, {0x158eff8, 0xc000436640}, 0xc0004f1570)
        pkg/sentry/kernel/task_start.go:122 +0xa5

====== kernel.signalHandlersMutex -> kernel.taskMutex =====
gvisor.dev/gvisor/pkg/sentry/kernel.(*TaskSet).newTask(0xc00019cea0, 0xc0004f1570)
        pkg/sentry/kernel/task_start.go:228 +0x9a8
gvisor.dev/gvisor/pkg/sentry/kernel.(*TaskSet).NewTask(0xc00014f180, {0x158eff8, 0xc000436640}, 0xc0004f1570)
        pkg/sentry/kernel/task_start.go:122 +0xa5
gvisor.dev/gvisor/pkg/sentry/kernel.(*Kernel).CreateProcess(0xc00014f180, {{0xc00039bf70, 0x5}, {0x0, 0x0}, {0xc00037d440, 0x1, 0x4}, {0xc000436620, 0x2, ...}, ...})
        pkg/sentry/kernel/kernel.go:1069 +0x147d
gvisor.dev/gvisor/runsc/boot.(*Loader).createContainerProcess(0xc0003f2000, 0x1, {0x7fff0a092fb9, 0x8}, 0xc0003f2010)
        runsc/boot/loader.go:809 +0x445
gvisor.dev/gvisor/runsc/boot.(*Loader).run(0xc0003f2000)
        runsc/boot/loader.go:630 +0x1ad
gvisor.dev/gvisor/runsc/boot.(*Loader).Run(0xc0003f2000)
        runsc/boot/loader.go:581 +0x25
This commit is contained in:
Andrei Vagin
2022-04-14 23:08:13 -07:00
parent 717f78b014
commit da439ae2f4
1 changed files with 35 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/sentry/kernel/fd_table.go
+35 -14
View File
@@ -241,28 +241,49 @@ func (f *FDTable) forEach(ctx context.Context, fn func(fd int32, file *fs.File,
func (f *FDTable) String() string {
var buf strings.Builder
ctx := context.Background()
files := make(map[int32]*fs.File)
filesVFS2 := make(map[int32]*vfs.FileDescription)
f.mu.Lock()
defer f.mu.Unlock()
// Can't release f.mu from defer, because vfsObj.PathnameWithDeleted
// should not be called under the fdtable mutex.
f.forEach(ctx, func(fd int32, file *fs.File, fileVFS2 *vfs.FileDescription, flags FDFlags) {
switch {
case file != nil:
n, _ := file.Dirent.FullName(nil /* root */)
fmt.Fprintf(&buf, "\tfd:%d => name %s\n", fd, n)
file.IncRef()
files[fd] = file
case fileVFS2 != nil:
vfsObj := fileVFS2.Mount().Filesystem().VirtualFilesystem()
vd := fileVFS2.VirtualDentry()
if vd.Dentry() == nil {
panic(fmt.Sprintf("fd %d (type %T) has nil dentry: %#v", fd, fileVFS2.Impl(), fileVFS2))
}
name, err := vfsObj.PathnameWithDeleted(ctx, vfs.VirtualDentry{}, fileVFS2.VirtualDentry())
if err != nil {
fmt.Fprintf(&buf, "<err: %v>\n", err)
return
}
fmt.Fprintf(&buf, "\tfd:%d => name %s\n", fd, name)
fileVFS2.IncRef()
filesVFS2[fd] = fileVFS2
}
})
f.mu.Unlock()
defer func() {
for _, f := range files {
f.DecRef(ctx)
}
for _, f := range filesVFS2 {
f.DecRef(ctx)
}
}()
for fd, file := range files {
n, _ := file.Dirent.FullName(nil /* root */)
fmt.Fprintf(&buf, "\tfd:%d => name %s\n", fd, n)
}
for fd, fileVFS2 := range filesVFS2 {
vfsObj := fileVFS2.Mount().Filesystem().VirtualFilesystem()
vd := fileVFS2.VirtualDentry()
if vd.Dentry() == nil {
panic(fmt.Sprintf("fd %d (type %T) has nil dentry: %#v", fd, fileVFS2.Impl(), fileVFS2))
}
name, err := vfsObj.PathnameWithDeleted(ctx, vfs.VirtualDentry{}, fileVFS2.VirtualDentry())
if err != nil {
fmt.Fprintf(&buf, "<err: %v>\n", err)
continue
}
fmt.Fprintf(&buf, "\tfd:%d => name %s\n", fd, name)
}
return buf.String()
}