os: File.Write panic: runtime error: slice bounds out of range

[syndtr]

What does 'go version' print?

go1.3.3 linux/arm

What steps reproduce the problem?

This happen on Android.
I believe for some reason syscall.Write returns syscall.EINTR error with invalid length,
but I'm not exactly sure what causing this (hardware failure? kernel bug?).

What happened?

panic: runtime error: slice bounds out of range

goroutine 27 [running]:
    /home/vagrant/build/com.nutomic.syncthingandroid/build/go/src/pkg/runtime/panic.c:248 +0xe0
os.(*File).write(0x119a8a30, 0x11a77500, 0xafb, 0x1371, 0xffffffff, 0x0, 0x0)
    /home/vagrant/build/com.nutomic.syncthingandroid/build/go/src/pkg/os/file_unix.go:218 +0xe4
os.(*File).Write(0x119a8a30, 0x11a77500, 0xafb, 0x1371, 0x0, 0x0, 0x0)
    /home/vagrant/build/com.nutomic.syncthingandroid/build/go/src/pkg/os/file.go:139 +0x88
github.com/syndtr/goleveldb/leveldb/table.(*Writer).writeBlock(0x1168e800, 0x1168e82c,
0x2, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0)
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table/writer.go:190 +0x41c
github.com/syndtr/goleveldb/leveldb/table.(*Writer).finishBlock(0x1168e800, 0x0, 0x0)
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table/writer.go:225 +0x98
github.com/syndtr/goleveldb/leveldb/table.(*Writer).Append(0x1168e800, 0x1146b080, 0x9f,
0x160, 0x11d3b002, 0x4, 0x1004, 0x0, 0x0)
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table/writer.go:258 +0x300
github.com/syndtr/goleveldb/leveldb.(*tWriter).append(0x11f94270, 0x1146b080, 0x9f,
0x160, 0x11d3b002, 0x4, 0x1004, 0x0, 0x0)
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/table.go:481 +0x2c8
github.com/syndtr/goleveldb/leveldb.func·018(0x11869a70, 0x0, 0x0)
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db_compaction.go:432 +0x794
github.com/syndtr/goleveldb/leveldb.(*DB).compactionTransact(0x109fe380, 0x481b18, 0xb,
0x114a7e34, 0x114a7dac)
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db_compaction.go:173 +0x1c8
github.com/syndtr/goleveldb/leveldb.(*DB).tableCompaction(0x109fe380, 0x119f2200,
0x1fef00)
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db_compaction.go:301 +0xbd4
github.com/syndtr/goleveldb/leveldb.(*DB).tableAutoCompaction(0x109fe380)
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db_compaction.go:516 +0x54
github.com/syndtr/goleveldb/leveldb.(*DB).tCompaction(0x109fe380)
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db_compaction.go:687 +0x280
created by github.com/syndtr/goleveldb/leveldb.openDB
    /home/vagrant/build/com.nutomic.syncthingandroid/ext/syncthing/src/github.com/syncthing/syncthing/Godeps/_workspace/src/github.com/syndtr/goleveldb/leveldb/db.go:126 +0x500

What should have happened instead?

Not panic'ing.

[ianlancetaylor]

Comment 1:

I think the code in os is just wrong.  syscall.Write can easily return -1, EINTR.  Or I
suppose we could say that the code in syscall is wrong, but many of the syscalls can
return a non-zero value along with a non-nil error.

Labels changed: added repo-main, release-go1.4.

[ianlancetaylor]

Comment 2:

Can you use strace to verify that write is returning EINTR?  Because, on further
reflection, all the signal handlers are installed with SA_RESTART set, so the write
should restart, not fail.

[rsc]

Comment 3:

This issue was closed by revision a62da20.

Status changed to Fixed.

[syndtr]

Comment 4:

> Can you use strace to verify that write is returning EINTR?  Because, on further
reflection, all the signal handlers are installed with SA_RESTART set, so the write
should restart, not fail.
I'm afraid I can't provide you with strace since I'm not exactly experience this myself,
but an user does. But I believe EINTR is only possible error that would trigger this
panic (i.e. nil or other error wouldn't skip sanity check).

[ianlancetaylor]

Comment 5:

I agree that I can't see any way this could fail other than EINTR, but I would still
like to confirm that that is happening.  Because it should be impossible.  If it is
possible there are likely other things that will need to be fixed.  If you can get more
information from the user, that would be very helpful.  Thanks.

[syndtr]

Comment 6:

I see. Anyway, here is the issue related to this
syndtr/goleveldb#80.