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contentenc: reserve one extra block in pool plaintext buffers 

File holes and -fsck can cause unaligned read accesses, which means
we have to decrypt one extra plaintext block.

xfstests generic/083 manage to crash -fsck like this:

generic/083	2018/07/14 15:25:21 wrong len=266240, want=131072
panic: wrong len=266240, want=131072

goroutine 1 [running]:
log.Panicf(0x67fc00, 0x15, 0xc4204fec90, 0x2, 0x2)
	/usr/local/go/src/log/log.go:333 +0xda
github.com/rfjakob/gocryptfs/internal/contentenc.(*bPool).Put(0xc4200d4800, 0xc4202f2000, 0x21000, 0x41000)
	/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/contentenc/bpool.go:27 +0x15d
github.com/rfjakob/gocryptfs/internal/fusefrontend.(*File).doRead(0xc4200b4500, 0xc42019e000, 0x0, 0x20000, 0x28400, 0x20000, 0xc42019e000, 0xc4204ff008, 0x435164, 0xc420000180)
	/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/fusefrontend/file.go:227 +0xba9
github.com/rfjakob/gocryptfs/internal/fusefrontend.(*File).Read(0xc4200b4500, 0xc42019e000, 0x20000, 0x20000, 0x28400, 0x0, 0x0, 0x0)
	/home/jakob/go/src/github.com/rfjakob/gocryptfs/internal/fusefrontend/file.go:246 +0x23e
main.(*fsckObj).file(0xc420069320, 0xc42001a630, 0x21)
	/home/jakob/go/src/github.com/rfjakob/gocryptfs/fsck.go:126 +0x21f
main.(*fsckObj).dir(0xc420069320, 0xc420014dc0, 0x1d)
	/home/jakob/go/src/github.com/rfjakob/gocryptfs/fsck.go:76 +0x387
main.(*fsckObj).dir(0xc420069320, 0xc42021dae0, 0x19)
	/home/jakob/go/src/github.com/rfjakob/gocryptfs/fsck.go:74 +0x347
This commit is contained in:
Jakob Unterwurzacher 2018-07-15 11:39:07 +02:00
parent 38f79a1abc
commit bcca323cb7
1 changed files with 9 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
internal/contentenc/content.go
View File

@ -71,15 +71,17 @@ type ContentEnc struct {
// New returns an initialized ContentEnc instance.
func New(cc *cryptocore.CryptoCore, plainBS uint64, forceDecode bool) *ContentEnc {
cipherBS := plainBS + uint64(cc.IVLen) + cryptocore.AuthTagLen
// Take IV and GHASH overhead into account.
cReqSize := int(fuse.MAX_KERNEL_WRITE / plainBS * cipherBS)
// An unaligned read (could happen with O_DIRECT?) may touch one
// additional ciphertext block. Reserve space for it.
cReqSize += int(cipherBS)
if fuse.MAX_KERNEL_WRITE%plainBS != 0 {
log.Panicf("unaligned MAX_KERNEL_WRITE=%d", fuse.MAX_KERNEL_WRITE)
}
cipherBS := plainBS + uint64(cc.IVLen) + cryptocore.AuthTagLen
// Take IV and GHASH overhead into account.
cReqSize := int(fuse.MAX_KERNEL_WRITE / plainBS * cipherBS)
// Unaligned reads (happens during fsck, could also happen with O_DIRECT?)
// touch one additional ciphertext and plaintext block. Reserve space for the
// extra block.
cReqSize += int(cipherBS)
pReqSize := fuse.MAX_KERNEL_WRITE + int(plainBS)
c := &ContentEnc{
cryptoCore: cc,
plainBS: plainBS,
@ -90,7 +92,7 @@ func New(cc *cryptocore.CryptoCore, plainBS uint64, forceDecode bool) *ContentEn
cBlockPool: newBPool(int(cipherBS)),
CReqPool: newBPool(cReqSize),
pBlockPool: newBPool(int(plainBS)),
PReqPool: newBPool(fuse.MAX_KERNEL_WRITE),
PReqPool: newBPool(pReqSize),
}
return c
}