The core ptrace access checking routine holds a task lock, and when reporting a failure, Yama takes a separate task lock. To avoid a potential deadlock with two ptracers taking the opposite locks, do not use get_task_comm() and just use ->comm directly since accuracy is not important for the report.
Reported-by: Fengguang Wu <[email protected]> Suggested-by: Oleg Nesterov <[email protected]> CC: [email protected] Signed-off-by: Kees Cook <[email protected]> Acked-by: John Johansen <[email protected]> --- v2: update with newly added traceme report. --- security/yama/yama_lsm.c | 10 ++-------- 1 files changed, 2 insertions(+), 8 deletions(-) diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c index d51b7c7..0cc99a3 100644 --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -279,12 +279,9 @@ static int yama_ptrace_access_check(struct task_struct *child, } if (rc) { - char name[sizeof(current->comm)]; printk_ratelimited(KERN_NOTICE "ptrace of pid %d was attempted by: %s (pid %d)\n", - child->pid, - get_task_comm(name, current), - current->pid); + child->pid, current->comm, current->pid); } return rc; @@ -319,12 +316,9 @@ static int yama_ptrace_traceme(struct task_struct *parent) } if (rc) { - char name[sizeof(current->comm)]; printk_ratelimited(KERN_NOTICE "ptraceme of pid %d was attempted by: %s (pid %d)\n", - current->pid, - get_task_comm(name, parent), - parent->pid); + current->pid, parent->comm, parent->pid); } return rc; -- 1.7.0.4 -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
