In the Linux kernel, the following vulnerability has been resolved:
tracefs: Reset permissions on remount if permissions are options
There’s an inconsistency with the way permissions are handled in tracefs.
Because the permissions are generated when accessed, they default to the
root inode’s permission if they were never set by the user. If the user
sets the permissions, then a flag is set and the permissions are saved via
the inode (for tracefs files) or an internal attribute field (for
eventfs).
But if a remount happens that specify the permissions, all the files that
were not changed by the user gets updated, but the ones that were are not.
If the user were to remount the file system with a given permission, then
all files and directories within that file system should be updated.
This can cause security issues if a file’s permission was updated but the
admin forgot about it. They could incorrectly think that remounting with
permissions set would update all files, but miss some.
For example:
[…]
-rw-r----- 1 root root 0 May 1 21:25 buffer_size_kb
-rw-r----- 1 root root 0 May 1 21:25 buffer_subbuf_size_kb
-r–r----- 1 root root 0 May 1 21:25 buffer_total_size_kb
-rw-r----- 1 root lkp 0 May 1 21:25 current_tracer
-rw-r----- 1 root root 0 May 1 21:25 dynamic_events
-r–r----- 1 root root 0 May 1 21:25 dyn_ftrace_total_info
-r–r----- 1 root root 0 May 1 21:25 enabled_functions
Where current_tracer now has group “lkp”.
-rw-r----- 1 root tracing 0 May 1 21:25 buffer_size_kb
-rw-r----- 1 root tracing 0 May 1 21:25 buffer_subbuf_size_kb
-r–r----- 1 root tracing 0 May 1 21:25 buffer_total_size_kb
-rw-r----- 1 root lkp 0 May 1 21:25 current_tracer
-rw-r----- 1 root tracing 0 May 1 21:25 dynamic_events
-r–r----- 1 root tracing 0 May 1 21:25 dyn_ftrace_total_info
-r–r----- 1 root tracing 0 May 1 21:25 enabled_functions
Everything changed but the “current_tracer”.
Add a new link list that keeps track of all the tracefs_inodes which has
the permission flags that tell if the file/dir should use the root inode’s
permission or not. Then on remount, clear all the flags so that the
default behavior of using the root inode’s permission is done for all
files and directories.
OS | Version | Architecture | Package | Version | Filename |
---|---|---|---|---|---|
ubuntu | 18.04 | noarch | linux | < any | UNKNOWN |
ubuntu | 20.04 | noarch | linux | < any | UNKNOWN |
ubuntu | 22.04 | noarch | linux | < any | UNKNOWN |
ubuntu | 23.10 | noarch | linux | < any | UNKNOWN |
ubuntu | 24.04 | noarch | linux | < any | UNKNOWN |
ubuntu | 14.04 | noarch | linux | < any | UNKNOWN |
ubuntu | 16.04 | noarch | linux | < any | UNKNOWN |
ubuntu | 18.04 | noarch | linux-aws | < any | UNKNOWN |
ubuntu | 20.04 | noarch | linux-aws | < any | UNKNOWN |
ubuntu | 22.04 | noarch | linux-aws | < any | UNKNOWN |
git.kernel.org/linus/baa23a8d4360d981a49913841a726edede5cdd54 (6.9-rc7)
git.kernel.org/stable/c/414fb08628143203d29ccd0264b5a83fb9523c03
git.kernel.org/stable/c/5f91fc82794d4a6e41cdcd02d00baa377d94ca78
git.kernel.org/stable/c/baa23a8d4360d981a49913841a726edede5cdd54
launchpad.net/bugs/cve/CVE-2024-36963
nvd.nist.gov/vuln/detail/CVE-2024-36963
security-tracker.debian.org/tracker/CVE-2024-36963
www.cve.org/CVERecord?id=CVE-2024-36963