avoid return NULL on root rb_node in rb_next/rb_prev in lib/rbtree.c
in [Kernel]
|
Prev: [PATCH] arch/x86/kernel/cpu/mtrr/cleanup.c: Use ";" not "," to terminate statements
Next: BUG in drivers/dma/ioat/dma_v2.c:314
From: shenghui on 28 Jun 2010 19:50 2010/6/28 Peter Zijlstra <peterz(a)infradead.org>: > So if ->rb_leftmost is NULL, then the if (!left) check in > __pick_next_entity() would return null. > > As to the NULL deref in in pick_next_task_fair()->set_next_entity() that > should never happen because pick_next_task_fair() will bail > on !->nr_running. > > Furthermore, you've failed to mention what kernel version you're looking > at. > The kernel version is 2.6.35-rc3, and 2.6.34 has the same code. For nr->running, if current is the only process in the run queue, then nr->running would not be zero. 1784 if (!cfs_rq->nr_running) 1785 return NULL; pick_next_task_fair() could pass above check and run to following: 1787 do { 1788 se = pick_next_entity(cfs_rq); 1789 set_next_entity(cfs_rq, se); 1790 cfs_rq = group_cfs_rq(se); 1791 } while (cfs_rq); Then pick_next_entity will get NULL for current is the root rb_node. Then set_next_entity would fail on NULL deference. -- Thanks and Best Regards, shenghui -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: shenghui on 29 Jun 2010 03:10
2010/6/29 shenghui <crosslonelyover(a)gmail.com>: > 2010/6/28 Peter Zijlstra <peterz(a)infradead.org>: >> So if ->rb_leftmost is NULL, then the if (!left) check in >> __pick_next_entity() would return null. >> >> As to the NULL deref in in pick_next_task_fair()->set_next_entity() that >> should never happen because pick_next_task_fair() will bail >> on !->nr_running. >> >> Furthermore, you've failed to mention what kernel version you're looking >> at. >> > > The kernel version is 2.6.35-rc3, and 2.6.34 has the same code. > > For nr->running, if current is the only process in the run queue, then > nr->running would not be zero. > 1784 if (!cfs_rq->nr_running) > 1785 return NULL; > pick_next_task_fair() could pass above check and run to following: > 1787 do { > 1788 se = pick_next_entity(cfs_rq); > 1789 set_next_entity(cfs_rq, se); > 1790 cfs_rq = group_cfs_rq(se); > 1791 } while (cfs_rq); > > Then pick_next_entity will get NULL for current is the root rb_node. > Then set_next_entity would fail on NULL deference. > Sorry, I misunderstood the code. I'll put forward one new patch to avoid the NULL condition -- Thanks and Best Regards, shenghui -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |