procfs: release the file system mutex on the error path

avagin · gvisor-bot · commit 6448dbe1b799 · 2025-09-18T15:23:35.000-07:00
Reported-by: syzbot+7b4d0fefa2463e53c401@syzkaller.appspotmail.com
PiperOrigin-RevId: 808759083
diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go
@@ -530,6 +530,7 @@ func (fs *Filesystem) OpenAt(ctx context.Context, rp *vfs.ResolvingPath, opts vf
 		}
 		if trunc && d.isRegular() {
 			if err := mnt.CheckBeginWrite(); err != nil {
+				fs.mu.RUnlock()
 				return nil, err
 			}
 			defer mnt.EndWrite()

Original file line number	Diff line number	Diff line change
`@@ -530,6 +530,7 @@ func (fs Filesystem) OpenAt(ctx context.Context, rp vfs.ResolvingPath, opts vf`
`530`	`530`	`}`
`531`	`531`	`if trunc && d.isRegular() {`
`532`	`532`	`if err := mnt.CheckBeginWrite(); err != nil {`
	`533`	`+ fs.mu.RUnlock()`
`533`	`534`	`return nil, err`
`534`	`535`	`}`
`535`	`536`	`defer mnt.EndWrite()`