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Yama: access task_struct->comm directly

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 <fengguang.wu@intel.com>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
CC: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
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1 parent d987569 commit 7612bfeecc197bbb6629842b5c6ff1967f0a9b70 @kees kees committed with James Morris Aug 15, 2012
Showing with 2 additions and 8 deletions.
  1. +2 −8 security/yama/yama_lsm.c
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@@ -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;

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