linux-kernel - Bug at kernel/cred.c +432

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-next>] [day] [month] [year] [list]

Date:   Mon, 09 Sep 2019 15:47:17 -0700
From:   rishabhb@...eaurora.org
To:     miklos@...redi.hu, linux-unionfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     tsoni@...eaurora.org, psodagud@...eaurora.org,
        jshriram@...eaurora.org
Subject: Bug at kernel/cred.c +432

Hi Miklos

In 4.19 kernel when we write to a file that doesn't exist we see the
following stack:
[  377.382745]  ovl_create_or_link+0xac/0x710
[  377.382745]  ovl_create_object+0xb8/0x110
[  377.382745]  ovl_create+0x34/0x40
[  377.382745]  path_openat+0xd44/0x15a8
[  377.382745]  do_filp_open+0x80/0x128
[  377.382745]  do_sys_open+0x140/0x250
[  377.382745]  __arm64_sys_openat+0x2c/0x38

If the override_cred flag = off, the ovl_override_cred and 
ovl_revert_cred just returns NULL.
But there is another override_cred in between these two functions;
		put_cred(override_creds(override_cred));
		put_cred(override_cred);

This will override the credentials permanently as there is no 
corresponding revert_cred associated.
So whenever we do commit_creds for this task, we see a BUG_ON at 
kernel/cred.c +443.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/cred.c#n443

Should this override_cred be changed to ovl_override_cred to maintain 
consistency and avoid this
BUG_ON?


Thanks,
Rishabh