blob/s3blob: nil pointer dereference for range reader error path #3424
Description
Describe the bug
Panic caused by nil pointer dereference in blob Reader after error in Read.
Debugging this it seems this is caused by Reader entering an invalid state:
Readis called and we reach line 147 (in version0.37.0) andNewRangeReaderreturns an error:
r.r, err = r.b.NewRangeReader(r.ctx, r.key, r.baseOffset+r.relativeOffset, length, r.dopts)
if err != nil {
return 0, wrapError(r.b, err, r.key)
}
- r.r is now
nil. Seek(which doesn't validate the object) is later called for the reader, we reachSizeandr.r.Attributes().Sizepanics.
To Reproduce
Managed to reproduce this 100% of the time in a nonsensical way with context canceling:
package main
import (
"context"
"io"
awsv2cfg "github.com/aws/aws-sdk-go-v2/config"
"github.com/aws/aws-sdk-go-v2/credentials"
s3v2 "github.com/aws/aws-sdk-go-v2/service/s3"
"gocloud.dev/blob"
"gocloud.dev/blob/s3blob"
)
const (
AWS_ACCESS_KEY_ID = "XXXXX"
AWS_SECRET_ACCESS_KEY = "XXXXX"
AWS_SESSION_TOKEN = "XXXXX"
)
func main() {
ctx, cancelFunc := context.WithCancel(context.Background())
client := openClient(ctx)
bucket, err := s3blob.OpenBucketV2(ctx, client, "test", nil)
if err != nil {
panic(err)
}
reader, err := bucket.NewRangeReader(ctx, "test.yaml", 0, 1024, &blob.ReaderOptions{})
if err != nil {
panic(err)
}
b := make([]byte, 512)
_, err = reader.Read(b)
if err != nil {
panic(err)
}
_, err = reader.Seek(0, io.SeekStart)
if err != nil {
panic(err)
}
cancelFunc()
_, _ = reader.Read(b)
_, err = reader.Seek(0, io.SeekEnd)
if err != nil {
panic(err)
}
}
func openClient(ctx context.Context) *s3v2.Client {
funcs := setAWSLoadOptions()
cfg, err := awsv2cfg.LoadDefaultConfig(ctx, funcs...)
if err != nil {
panic(err)
}
return s3v2.NewFromConfig(cfg)
}
func setAWSLoadOptions() []func(*awsv2cfg.LoadOptions) error {
funcs := []func(*awsv2cfg.LoadOptions) error{awsv2cfg.WithRegion("us-east-1")}
funcs = append(funcs, awsv2cfg.WithCredentialsProvider(credentials.NewStaticCredentialsProvider(
AWS_ACCESS_KEY_ID,
AWS_SECRET_ACCESS_KEY,
AWS_SESSION_TOKEN)))
return funcs
}
Traceback:
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x20 pc=0x100e5f840]
goroutine 1 [running]:
gocloud.dev/blob.(*Reader).Size(0x140004c0000)
/Users/user/go/pkg/mod/gocloud.dev@v0.37.0/blob/blob.go:222 +0x140
gocloud.dev/blob.(*Reader).Seek(0x140004c0000, 0x0, 0x2)
/Users/user/go/pkg/mod/gocloud.dev@v0.37.0/blob/blob.go:169 +0x40
main.main()
/Users/user/dev/example.go:49 +0x128
Process finished with the exit code 2
Expected behavior
Expected an error and not to panic.
Version
gocloud 0.37.0
Additional context
The original program consists of a lot of goroutines working on the reader with locks, the use itself is not ideal but at the very least it probably shouldn't crash. I would expect that if one gorountines errors (say from timeout getting context deadline exceeded) another goroutine using it would also get an error and not panic.