From 1321f837bd9f082e3c1b0a37831453b3637202c3 Mon Sep 17 00:00:00 2001 From: Dean Deng Date: Mon, 2 Nov 2020 22:30:23 -0800 Subject: [vfs2] Refactor kernfs checkCreateLocked. 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 --- pkg/sentry/fsimpl/kernfs/filesystem.go | 43 +++++++++++++++++----------------- 1 file changed, 21 insertions(+), 22 deletions(-) diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go index f81056023..50aeab908 100644 --- a/pkg/sentry/fsimpl/kernfs/filesystem.go +++ b/pkg/sentry/fsimpl/kernfs/filesystem.go @@ -207,24 +207,23 @@ func (fs *Filesystem) walkParentDirLocked(ctx context.Context, rp *vfs.Resolving // Preconditions: // * Filesystem.mu must be locked for at least reading. // * isDir(parentInode) == true. -func checkCreateLocked(ctx context.Context, rp *vfs.ResolvingPath, parent *Dentry) (string, error) { - if err := parent.inode.CheckPermissions(ctx, rp.Credentials(), vfs.MayWrite|vfs.MayExec); err != nil { - return "", err +func checkCreateLocked(ctx context.Context, creds *auth.Credentials, name string, parent *Dentry) error { + if err := parent.inode.CheckPermissions(ctx, creds, vfs.MayWrite|vfs.MayExec); err != nil { + return err } - pc := rp.Component() - if pc == "." || pc == ".." { - return "", syserror.EEXIST + if name == "." || name == ".." { + return syserror.EEXIST } - if len(pc) > linux.NAME_MAX { - return "", syserror.ENAMETOOLONG + if len(name) > linux.NAME_MAX { + return syserror.ENAMETOOLONG } - if _, ok := parent.children[pc]; ok { - return "", syserror.EEXIST + if _, ok := parent.children[name]; ok { + return syserror.EEXIST } if parent.VFSDentry().IsDead() { - return "", syserror.ENOENT + return syserror.ENOENT } - return pc, nil + return nil } // checkDeleteLocked checks that the file represented by vfsd may be deleted. @@ -352,8 +351,8 @@ func (fs *Filesystem) LinkAt(ctx context.Context, rp *vfs.ResolvingPath, vd vfs. parent.dirMu.Lock() defer parent.dirMu.Unlock() - pc, err := checkCreateLocked(ctx, rp, parent) - if err != nil { + pc := rp.Component() + if err := checkCreateLocked(ctx, rp.Credentials(), pc, parent); err != nil { return err } if rp.Mount() != vd.Mount() { @@ -394,8 +393,8 @@ func (fs *Filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts v parent.dirMu.Lock() defer parent.dirMu.Unlock() - pc, err := checkCreateLocked(ctx, rp, parent) - if err != nil { + pc := rp.Component() + if err := checkCreateLocked(ctx, rp.Credentials(), pc, parent); err != nil { return err } if err := rp.Mount().CheckBeginWrite(); err != nil { @@ -430,8 +429,8 @@ func (fs *Filesystem) MknodAt(ctx context.Context, rp *vfs.ResolvingPath, opts v parent.dirMu.Lock() defer parent.dirMu.Unlock() - pc, err := checkCreateLocked(ctx, rp, parent) - if err != nil { + pc := rp.Component() + if err := checkCreateLocked(ctx, rp.Credentials(), pc, parent); err != nil { return err } if err := rp.Mount().CheckBeginWrite(); err != nil { @@ -657,8 +656,8 @@ func (fs *Filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa // Can we create the dst dentry? var dst *Dentry - pc, err := checkCreateLocked(ctx, rp, dstDir) - switch err { + pc := rp.Component() + switch err := checkCreateLocked(ctx, rp.Credentials(), pc, dstDir); err { case nil: // Ok, continue with rename as replacement. case syserror.EEXIST: @@ -822,8 +821,8 @@ func (fs *Filesystem) SymlinkAt(ctx context.Context, rp *vfs.ResolvingPath, targ parent.dirMu.Lock() defer parent.dirMu.Unlock() - pc, err := checkCreateLocked(ctx, rp, parent) - if err != nil { + pc := rp.Component() + if err := checkCreateLocked(ctx, rp.Credentials(), pc, parent); err != nil { return err } if err := rp.Mount().CheckBeginWrite(); err != nil { -- cgit v1.2.3