From 0476fd4ff45261744da6bb2df2f8080571902bf0 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Tue, 17 Dec 2024 18:55:32 +0900 Subject: [PATCH] tomoyo: use realpath if symlink's pathname refers to procfs Fedora 41 has reached Linux 6.12 kernel with TOMOYO enabled. I observed that /usr/lib/systemd/systemd executes /usr/lib/systemd/systemd-executor by passing dirfd == 9 or dirfd == 16 upon execveat(). Commit ada1986d0797 ("tomoyo: fallback to realpath if symlink's pathname does not exist") used realpath only if symlink's pathname does not exist. But an out of tree patch suggested that it will be reasonable to always use realpath if symlink's pathname refers to proc filesystem. Therefore, this patch changes the pathname used for checking "file execute" and the domainname used after a successful execve() request. Before: /usr/lib/systemd/systemd file execute proc:/self/fd/16 exec.realpath="/usr/lib/systemd/systemd-executor" exec.argv[0]="/usr/lib/systemd/systemd-executor" file execute proc:/self/fd/9 exec.realpath="/usr/lib/systemd/systemd-executor" exec.argv[0]="/usr/lib/systemd/systemd-executor" /usr/lib/systemd/systemd proc:/self/fd/16 file execute /usr/sbin/auditd exec.realpath="/usr/sbin/auditd" exec.argv[0]="/usr/sbin/auditd" /usr/lib/systemd/systemd proc:/self/fd/16 /usr/sbin/auditd /usr/lib/systemd/systemd proc:/self/fd/9 file execute /usr/bin/systemctl exec.realpath="/usr/bin/systemctl" exec.argv[0]="/usr/bin/systemctl" /usr/lib/systemd/systemd proc:/self/fd/9 /usr/bin/systemctl After: /usr/lib/systemd/systemd file execute /usr/lib/systemd/systemd-executor exec.realpath="/usr/lib/systemd/systemd-executor" exec.argv[0]="/usr/lib/systemd/systemd-executor" /usr/lib/systemd/systemd /usr/lib/systemd/systemd-executor file execute /usr/bin/systemctl exec.realpath="/usr/bin/systemctl" exec.argv[0]="/usr/bin/systemctl" file execute /usr/sbin/auditd exec.realpath="/usr/sbin/auditd" exec.argv[0]="/usr/sbin/auditd" /usr/lib/systemd/systemd /usr/lib/systemd/systemd-executor /usr/bin/systemctl /usr/lib/systemd/systemd /usr/lib/systemd/systemd-executor /usr/sbin/auditd Signed-off-by: Tetsuo Handa --- security/tomoyo/domain.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/security/tomoyo/domain.c b/security/tomoyo/domain.c index aed9e3ef2c9ec..3a7b0874cf44d 100644 --- a/security/tomoyo/domain.c +++ b/security/tomoyo/domain.c @@ -722,10 +722,17 @@ int tomoyo_find_next_domain(struct linux_binprm *bprm) ee->bprm = bprm; ee->r.obj = &ee->obj; ee->obj.path1 = bprm->file->f_path; - /* Get symlink's pathname of program. */ + /* + * Get symlink's pathname of program, but fallback to realpath if + * symlink's pathname does not exist or symlink's pathname refers + * to proc filesystem (e.g. /dev/fd/ or /proc/self/fd/ ). + */ exename.name = tomoyo_realpath_nofollow(original_name); + if (exename.name && !strncmp(exename.name, "proc:/", 6)) { + kfree(exename.name); + exename.name = NULL; + } if (!exename.name) { - /* Fallback to realpath if symlink's pathname does not exist. */ exename.name = tomoyo_realpath_from_path(&bprm->file->f_path); if (!exename.name) goto out;