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procfs: block chmod on /proc/thread-self/comm 

commit ccf61486fe upstream.

Due to an oversight in commit 1b3044e39a ("procfs: fix pthread
cross-thread naming if !PR_DUMPABLE") in switching from REG to NOD,
chmod operations on /proc/thread-self/comm were no longer blocked as
they are on almost all other procfs files.

A very similar situation with /proc/self/environ was used to as a root
exploit a long time ago, but procfs has SB_I_NOEXEC so this is simply a
correctness issue.

Ref: https://lwn.net/Articles/191954/
Ref: 6d76fa58b0 ("Don't allow chmod() on the /proc/<pid>/ files")
Fixes: 1b3044e39a ("procfs: fix pthread cross-thread naming if !PR_DUMPABLE")
Cc: stable@vger.kernel.org # v4.7+
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Message-Id: <20230713141001.27046-1-cyphar@cyphar.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Aleksa Sarai 2023-07-14 00:09:58 +10:00 committed by Greg Kroah-Hartman
parent 4e3fc83581
commit bda2ed2b95
1 changed files with 2 additions and 1 deletions
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3
fs/proc/base.c
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@ -3583,7 +3583,8 @@ static int proc_tid_comm_permission(struct mnt_idmap *idmap,
}
static const struct inode_operations proc_tid_comm_inode_operations = {
.permission = proc_tid_comm_permission,
.setattr = proc_setattr,
.permission = proc_tid_comm_permission,
};
/*