linux-kernel - Re: bug#77597: listxattr() should return ENOTSUP for sysfs / tmpfs entries, not 0

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c0a1f475-b973-40a8-a7cc-6947791af38a@draigBrady.com>
Date: Fri, 23 May 2025 12:38:32 +0100
From: Pádraig Brady <P@...igBrady.com>
To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
 linux-security-module@...r.kernel.org
Cc: 77597@...bugs.gnu.org, Paul Eggert <eggert@...UCLA.EDU>,
 Rahul Sandhu <nvraxn@...il.com>
Subject: Re: bug#77597: listxattr() should return ENOTSUP for sysfs / tmpfs
 entries, not 0

On 23/04/2025 13:22, Pádraig Brady wrote:
> Older coreutils was less efficient and always called getxattr("security.selinux"),
> and thus shows the SELinux context as expected:
> 
>     $ coreutils-9.3/src/ls -lZd /run/initramfs
>     drwxr-xr-x. 3 root root system_u:object_r:tmpfs_t:s0 60 Apr 19 14:52 /run/initramfs
>     $ coreutils-9.3/src/ls -lZd /sys/block
>     drwxr-xr-x. 2 root root system_u:object_r:sysfs_t:s0 0 Apr 23 12:54 /sys/block
> 
> However newer coreutils is more efficient, and does not call getxattr()
> if listxattr() returns 0 indicating that there are no xattrs.
> 
>     $ coreutils-9.7/src/ls -lZd /run/initramfs
>     drwxr-xr-x 3 root root ? 60 Apr 19 14:52 /run/initramfs
>     $ coreutils-9.7/src/ls -lZd /sys/block
>     drwxr-xr-x 2 root root ? 0 Apr 23 12:54 /sys/block
> 
> I also noticed the same issue with the exa utility for example.
> For coreutils to maintain efficient processing and to fix the issue centrally,
> it would be more correct for listxattr() to return ENOTSUP,
> in which case ls will try the getxattr() call and operate as expected.
> Otherwise I can't see a way for coreutils to be both efficient and always correct.
> 
> I'm currently testing on kernel 6.14.2-300.fc42.x86_64

FYI this should be addressed with:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8b0ba61d

cheers,
Pádraig