Messages in this thread Patch in this message | | | Date | Mon, 12 May 2014 20:45:35 -0000 | From | Thomas Gleixner <> | Subject | [patch 3/3] futex: Prevent attaching to kernel threads |
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We happily allow userspace to declare a random kernel thread to be the owner of a user space PI futex.
Found while analysing the fallout of Dave Jones syscall fuzzer.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org --- kernel/futex.c | 7 +++++++ 1 file changed, 7 insertions(+)
Index: linux-2.6/kernel/futex.c =================================================================== --- linux-2.6.orig/kernel/futex.c +++ linux-2.6/kernel/futex.c @@ -682,6 +682,8 @@ static struct task_struct * futex_find_g p = find_task_by_vpid(pid); if (p) get_task_struct(p); + else + p = NULL; rcu_read_unlock(); @@ -814,6 +816,11 @@ lookup_pi_state(u32 uval, struct futex_h if (!p) return -ESRCH; + if (!p->mm) { + put_task_struct(p); + return -EPERM; + } + /* * We need to look at the task state flags to figure out, * whether the task is exiting. To protect against the do_exit
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