Re: [next-20130227] kernel NULL pointer dereference [ watchdog |perf related ? ]

From: Tejun Heo
Date: Wed Feb 27 2013 - 10:07:45 EST


Replying here too just in case.

On Wed, Feb 27, 2013 at 02:08:40PM +0100, Sedat Dilek wrote:
> >> static inline void *idr_find(struct idr *idr, int id)
> >> {
> >> struct idr_layer *hint = rcu_dereference_raw(idr->hint);
> >> 86d7: 48 8b 05 00 00 00 00 mov 0x0(%rip),%rax # 86de <perf_init_event+0x2e>
> >> 86da: R_X86_64_PC32 .bss+0xfc
> >>
> >> if ((id & ~IDR_MASK) == hint->prefix)
> >> 86de: 89 f2 mov %esi,%edx
> >> 86e0: 30 d2 xor %dl,%dl
> >> 86e2: 3b 10 cmp (%rax),%edx <--- trapping insn
> >> 86e4: 74 4a je 8730 <perf_init_event+0x80>
> >> return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
> >>
> >>
> >> So 'hint' is NULL as RAX above confirms and we're not supposed to deref
> >> NULL things.
> >>
> >> Looking at 29cf29e1fbb875019713eb55cf27ec35f1e5fa5e, Tejun should
> >> probably know. CCed.

Fix was posted some days ago.

http://thread.gmane.org/gmane.linux.kernel.next/26213

I got Andrew's patch added to -mm message a week ago. Not sure why it
still hasn't showed up. Andrew, any ideas?

Thanks.

--
tejun
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