In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path<\/p>\n
LANDLOCK_SCOPE_SIGNAL must prevent a sandboxed process from signaling
\nprocesses outside its Landlock domain. It can be bypassed through the
\nasynchronous SIGIO delivery path.<\/p>\n
A sandboxed process that owns any file or socket can arm it with
\nfcntl(fd, F_SETOWN, -pgid), fcntl(fd, F_SETSIG, SIGKILL) and O_ASYNC, so
\nthat an I\/O event makes the kernel deliver the chosen signal to the
\nwhole process group. As the head of its process group’s task list (the
\ndefault position right after fork()) that group can also hold the
\nnon-sandboxed process that launched it, e.g. a supervisor or a security
\nmonitor. The sandbox can thus kill or signal the processes
\nLANDLOCK_SCOPE_SIGNAL is meant to protect from it.<\/p>\n
The scope is enforced in hook_file_send_sigiotask() against the Landlock
\ndomain recorded at F_SETOWN time, not the live domain of the sender.
\ncontrol_current_fowner() decides whether to record that domain and skips
\nrecording it when the fowner target is in the caller’s thread group,
\nwhich is safe only for a single-task target (PIDTYPE_PID, PIDTYPE_TGID).
\nFor a process group (PIDTYPE_PGID) pid_task() returns only one member;
\nrecording is skipped whenever that member shares the caller’s thread
\ngroup, and hook_file_send_sigiotask() then lets the signal fan out to
\nthe whole group unchecked.<\/p>\n
Record the domain for every non single-process target so the scope is
\nenforced against each group member at delivery time.<\/p>\n
That recording is necessary but not sufficient on its own: the kernel
\nsignals a process group through its members’ thread-group leaders, and
\nthe leader of the registrant’s own process can carry a different
\nLandlock domain than the sibling thread that armed the owner.
\ndomain_is_scoped() would then deny that leader, even though commit
\n18eb75f3af40 (“landlock: Always allow signals between threads of the
\nsame process”) requires same-process delivery to be allowed.
\nhook_task_kill() avoids this by evaluating same_thread_group() live, per
\nrecipient; the SIGIO path instead delegates the whole decision to a
\nsingle registration-time check, which a process-group fan-out cannot
\nhonor.<\/p>\n
So also record the registrant’s thread group next to its domain and
\nexempt it at delivery: hook_file_send_sigiotask() allows the signal
\nwhenever the recipient belongs to the registrant’s own process,
\nrestoring the same-process guarantee while keeping out-of-domain group
\nmembers blocked. The direct kill() path (hook_task_kill) already
\nevaluates the live domain and is unaffected.<\/p>\n
[mic: Check pid_type earlier and improve comment, fix commit message,
\nfix comment formatting]<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
landlock: Fix LANDLOCK_SCOPE_SIGNAL bypass on the SIGIO path<\/p>\n
LANDLOCK_SCOPE_SIGNAL must prevent a sandboxed process from signaling<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-6819","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/6819","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6819"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6819"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6819"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}