From: Thomas Gleixner Date: Mon, 12 May 2014 20:45:34 +0000 (+0000) Subject: futex: Add another early deadlock detection check X-Git-Tag: omap-for-v3.16/fixes-against-rc1~117^2~2 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=866293ee54227584ffcb4a42f69c1f365974ba7f;p=pandora-kernel.git futex: Add another early deadlock detection check Dave Jones trinity syscall fuzzer exposed an issue in the deadlock detection code of rtmutex: http://lkml.kernel.org/r/20140429151655.GA14277@redhat.com That underlying issue has been fixed with a patch to the rtmutex code, but the futex code must not call into rtmutex in that case because - it can detect that issue early - it avoids a different and more complex fixup for backing out If the user space variable got manipulated to 0x80000000 which means no lock holder, but the waiters bit set and an active pi_state in the kernel is found we can figure out the recursive locking issue by looking at the pi_state owner. If that is the current task, then we can safely return -EDEADLK. The check should have been added in commit 59fa62451 (futex: Handle futex_pi OWNER_DIED take over correctly) already, but I did not see the above issue caused by user space manipulation back then. Signed-off-by: Thomas Gleixner Cc: Dave Jones Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Darren Hart Cc: Davidlohr Bueso Cc: Steven Rostedt Cc: Clark Williams Cc: Paul McKenney Cc: Lai Jiangshan Cc: Roland McGrath Cc: Carlos ODonell Cc: Jakub Jelinek Cc: Michael Kerrisk Cc: Sebastian Andrzej Siewior Link: http://lkml.kernel.org/r/20140512201701.097349971@linutronix.de Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org --- Reading git-diff-tree failed