accept() system call is inconsistent with bind(), connect()

[Daniel U. Thibault]

Under kernel 3.2.0-54 and 3.9.3 (at least), the accept() system call in a PF_LOCAL, AF_LOCAL, SOCK_STREAM context returns an addrlen for the sockaddr_un structure that is too large by one.

As the SUN_LEN macro of the sys/un.h header shows, the "length" of the structure is expected to be the strlen() of the sun_path member, plus that member's offset. This is the length used by bind() and connect(), in particular. But accept() consistently returns a "length" which includes the trailing null, and is thus too large by one.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-libc-dev 3.2.0-54.82
ProcVersionSignature: Ubuntu 3.2.0-54.82-virtual 3.2.50
Uname: Linux 3.2.0-54-virtual x86_64
AlsaDevices:
 total 0
 crw-rw---T 1 root audio 116, 1 May 26 09:41 seq
 crw-rw---T 1 root audio 116, 33 May 26 09:41 timer
AplayDevices: aplay: device_list:252: no soundcards found...
ApportVersion: 2.0.1-0ubuntu17.9
Architecture: amd64
ArecordDevices: arecord: device_list:252: no soundcards found...
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found.
Date: Tue Jun 9 16:14:40 2015
Dependencies:

HibernationDevice: RESUME=UUID=476a0cd7-3578-49f2-b064-1d2151aa9f56
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
IwConfig:
 lo no wireless extensions.

 eth0 no wireless extensions.
Lsusb:
 Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 001 Device 002: ID 80ee:0021 VirtualBox USB Tablet
MachineType: innotek GmbH VirtualBox
MarkForUpload: True
PciMultimedia:

ProcFB: 0 VESA VGA
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-54-virtual root=UUID=c1c9d001-671e-44c6-8e7c-82f83d591195 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.2.0-54-virtual N/A
 linux-backports-modules-3.2.0-54-virtual N/A
 linux-firmware 1.79.18
RfKill:

SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
WifiSyslog:

dmi.bios.date: 12/01/2006
dmi.bios.vendor: innotek GmbH
dmi.bios.version: VirtualBox
dmi.board.name: VirtualBox
dmi.board.vendor: Oracle Corporation
dmi.board.version: 1.2
dmi.chassis.type: 1
dmi.chassis.vendor: Oracle Corporation
dmi.modalias: dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:rvnOracleCorporation:rnVirtualBox:rvr1.2:cvnOracleCorporation:ct1:cvr:
dmi.product.name: VirtualBox
dmi.product.version: 1.2
dmi.sys.vendor: innotek GmbH

[Brad Figg (brad-figg)]

This change was made by a bot.

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.1 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream'.
Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.1-rc7-unstable/

[Daniel U. Thibault (daniel-thibault)]

Tried it under kernel 4.0.5-040005-generic_4.0.5-040005.201506061639_amd64, still there.

[Daniel U. Thibault (daniel-thibault)]

« Once testing of the upstream kernel is complete, please mark this bug as "Confirmed". »

As the reporter, I'm not allowed to do that. Besides, it's already marked as Confirmed.

[Daniel U. Thibault (daniel-thibault)]

I've just run into this related error (or discrepancy, at least) in the `unix(7)` man page:

"When the address of the socket is returned by getsockname(2), getpeername(2), and accept(2), its length is offsetof(struct sockaddr_un, sun_path) + strlen(sun_path) + 1, and sun_path contains the null-terminated pathname."

[penalvch (penalvch)]

Daniel U. Thibault, could you please test the latest mainline kernel as requested in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1463553/comments/3 ?

Also:
>"« Once testing of the upstream kernel is complete, please mark this bug as "Confirmed". » As the reporter, I'm not allowed to do that. Besides, it's already marked as Confirmed."

With linux (Ubuntu) a standing triaging exception is in place where Confirmed means the original reporter has at least attached the minimum amount of information to begin triaging.

[Daniel U. Thibault (daniel-thibault)]

Christopher, I did test the latest mainline kernel (4.0.5-040005-generic_4.0.5-040005.201506061639_amd64). Unless there's been another release over the last five days?