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fusefrontend: clamp oversized reads 

Our byte cache pools are sized acc. to MAX_KERNEL_WRITE, but the
running kernel may have a higher limit set. Clamp to what we can
handle.

Fixes a panic on a Synology NAS reported at
https://github.com/rfjakob/gocryptfs/issues/145
This commit is contained in:
Jakob Unterwurzacher 2017-10-17 21:47:32 +02:00
parent 64e5906ffa
commit 3009ec9852
2 changed files with 16 additions and 1 deletions
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2
internal/contentenc/content.go
View File

@ -194,6 +194,8 @@ func (be *ContentEnc) DecryptBlock(ciphertext []byte, blockNo uint64, fileID []b
const encryptMaxSplit = 2
// EncryptBlocks is like EncryptBlock but takes multiple plaintext blocks.
// Returns a byte slice from CReqPool - so don't forget to return it
// to the pool.
func (be *ContentEnc) EncryptBlocks(plaintextBlocks [][]byte, firstBlockNo uint64, fileID []byte) []byte {
ciphertextBlocks := make([][]byte, len(plaintextBlocks))
// For large writes, we parallelize encryption.

15
internal/fusefrontend/file.go
View File

@ -132,6 +132,8 @@ func (f *file) createHeader() (fileID []byte, err error) {
return h.ID, err
}
var oversizedReadWarn sync.Once
// doRead - read "length" plaintext bytes from plaintext offset "off" and append
// to "dst".
// Arguments "length" and "off" do not have to be block-aligned.
@ -142,6 +144,16 @@ func (f *file) createHeader() (fileID []byte, err error) {
// Called by Read() for normal reading,
// by Write() and Truncate() for Read-Modify-Write
func (f *file) doRead(dst []byte, off uint64, length uint64) ([]byte, fuse.Status) {
// Our byte cache pools are sized acc. to MAX_KERNEL_WRITE, but the
// running kernel may have a higher limit set. Clamp to what we can
// handle.
if length > fuse.MAX_KERNEL_WRITE {
oversizedReadWarn.Do(func() {
tlog.Warn.Printf("doRead: truncating oversized read: %d to %d bytes",
length, fuse.MAX_KERNEL_WRITE)
})
length = fuse.MAX_KERNEL_WRITE
}
// Make sure we have the file ID.
f.fileTableEntry.HeaderLock.RLock()
if f.fileTableEntry.ID == nil {
@ -170,7 +182,8 @@ func (f *file) doRead(dst []byte, off uint64, length uint64) ([]byte, fuse.Statu
blocks := f.contentEnc.ExplodePlainRange(off, length)
alignedOffset, alignedLength := blocks[0].JointCiphertextRange(blocks)
skip := blocks[0].Skip
tlog.Debug.Printf("JointCiphertextRange(%d, %d) -> %d, %d, %d", off, length, alignedOffset, alignedLength, skip)
tlog.Debug.Printf("doRead: off=%d len=%d -> off=%d len=%d skip=%d\n",
off, length, alignedOffset, alignedLength, skip)
ciphertext := f.fs.contentEnc.CReqPool.Get()
ciphertext = ciphertext[:int(alignedLength)]