From: Thomas Gleixner Date: Tue, 2 Feb 2010 10:40:27 +0000 (+0100) Subject: futex: Handle user space corruption gracefully X-Git-Tag: v2.6.33-rc7~13^2~1 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=51246bfd189064079c54421507236fd2723b18f3;p=pandora-kernel.git futex: Handle user space corruption gracefully If the owner of a PI futex dies we fix up the pi_state and set pi_state->owner to NULL. When a malicious or just sloppy programmed user space application sets the futex value to 0 e.g. by calling pthread_mutex_init(), then the futex can be acquired again. A new waiter manages to enqueue itself on the pi_state w/o damage, but on unlock the kernel dereferences pi_state->owner and oopses. Prevent this by checking pi_state->owner in the unlock path. If pi_state->owner is not current we know that user space manipulated the futex value. Ignore the mess and return -EINVAL. This catches the above case and also the case where a task hijacks the futex by setting the tid value and then tries to unlock it. Reported-by: Jermome Marchand Signed-off-by: Thomas Gleixner Acked-by: Darren Hart Acked-by: Peter Zijlstra Cc: --- Reading git-diff-tree failed