diff options
Diffstat (limited to 'cmd/sharefs/test/raceattr.go')
| -rw-r--r-- | cmd/sharefs/test/raceattr.go | 122 |
1 files changed, 0 insertions, 122 deletions
diff --git a/cmd/sharefs/test/raceattr.go b/cmd/sharefs/test/raceattr.go deleted file mode 100644 index 412cb2b3..00000000 --- a/cmd/sharefs/test/raceattr.go +++ /dev/null @@ -1,122 +0,0 @@ -//go:build raceattr - -// The raceattr program reproduces vfs inode file attribute race. -// -// Even though libfuse high-level API presents the address of a struct stat -// alongside struct fuse_context, file attributes are actually inherent to the -// inode, instead of the specific call from userspace. The kernel implementation -// in fs/fuse/xattr.c appears to make stale data in the inode (set by a previous -// call) impossible or very unlikely to reach userspace via the stat family of -// syscalls. However, when using default_permissions to have the VFS check -// permissions, this race still happens, despite the resulting struct stat being -// correct when overriding the check via capabilities otherwise. -// -// This program reproduces the failure, but because of its continuous nature, it -// is provided independent of the vm integration test suite. -package main - -import ( - "context" - "flag" - "log" - "os" - "os/signal" - "runtime" - "sync" - "sync/atomic" - "syscall" -) - -func newStatAs( - ctx context.Context, cancel context.CancelFunc, - n *atomic.Uint64, ok *atomic.Bool, - uid uint32, pathname string, - continuous bool, -) func() { - return func() { - runtime.LockOSThread() - defer cancel() - - if _, _, errno := syscall.Syscall( - syscall.SYS_SETUID, uintptr(uid), - 0, 0, - ); errno != 0 { - cancel() - log.Printf("cannot set uid to %d: %s", uid, errno) - } - - var stat syscall.Stat_t - for { - if ctx.Err() != nil { - return - } - - if err := syscall.Lstat(pathname, &stat); err != nil { - // SHAREFS_PERM_DIR not world executable, or - // SHAREFS_PERM_REG not world readable - if !continuous { - cancel() - } - ok.Store(true) - log.Printf("uid %d: %v", uid, err) - } else if stat.Uid != uid { - // appears to be unreachable - if !continuous { - cancel() - } - ok.Store(true) - log.Printf("got uid %d instead of %d", stat.Uid, uid) - } - n.Add(1) - } - } -} - -func main() { - log.SetFlags(0) - log.SetPrefix("raceattr: ") - - p := flag.String("target", "/sdcard/raceattr", "pathname of test file") - u0 := flag.Int("uid0", 1<<10-1, "first uid") - u1 := flag.Int("uid1", 1<<10-2, "second uid") - count := flag.Int("count", 1, "threads per uid") - continuous := flag.Bool("continuous", false, "keep running even after reproduce") - flag.Parse() - - if os.Geteuid() != 0 { - log.Fatal("this program must run as root") - } - - ctx, cancel := signal.NotifyContext( - context.Background(), - syscall.SIGINT, - syscall.SIGTERM, - syscall.SIGHUP, - ) - - if err := os.WriteFile(*p, nil, 0); err != nil { - log.Fatal(err) - } - - var ( - wg sync.WaitGroup - - n atomic.Uint64 - ok atomic.Bool - ) - - if *count < 1 { - *count = 1 - } - for range *count { - wg.Go(newStatAs(ctx, cancel, &n, &ok, uint32(*u0), *p, *continuous)) - if *u1 >= 0 { - wg.Go(newStatAs(ctx, cancel, &n, &ok, uint32(*u1), *p, *continuous)) - } - } - - wg.Wait() - if !*continuous && ok.Load() { - log.Printf("reproduced after %d calls", n.Load()) - } -} |
