Messages in this thread Patch in this message |  | | Subject | Re: [PATCH] add check do_direct_IO() return val | From | Badari Pulavarty <> | Date | Tue, 31 Jul 2007 15:25:11 -0700 |
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On Tue, 2007-07-31 at 12:35 +0800, Joe Jin wrote: > > Hmm.. in this config file, whats causing DIO to panic ? Which test actually > > passing faulty buffer ? > > > > By my testing, just defined job3 and job10 will also get the panic, but if > only have one of them, panic will not appear. the faulty buffer maybe passed > by mmap.
Okay. Here is the fix for the problem.
Here is whats happening in this case:
Faulty user-buffer caused -EFAULT to be returned from do_direct_IO(). We go into dio_zero_block() to see if we need to zero out sections of the block (if IO size < blocksize case). It checks if the buffer is newly allocation by doing buffer_new(bh). map_bh is NOT initialized and never went through get_block() code. So, its possible to pass the check and end up submitting a page wrongly and causing the oops.
Fix is to initialize the buffer state.
Thanks, Badari
Need to initialize map_bh.b_state to zero. Otherwise, in case of a faulty user-buffer its possible to go into dio_zero_block() and submit a page by mistake - since it checks for buffer_new().
http://marc.info/?l=linux-kernel&m=118551339032528&w=2
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com> --- fs/direct-io.c | 1 + 1 file changed, 1 insertion(+)
Index: linux-2.6.23-rc1/fs/direct-io.c =================================================================== --- linux-2.6.23-rc1.orig/fs/direct-io.c 2007-07-22 13:41:00.000000000 -0700 +++ linux-2.6.23-rc1/fs/direct-io.c 2007-07-31 15:13:44.000000000 -0700 @@ -974,6 +974,7 @@ direct_io_worker(int rw, struct kiocb *i dio->get_block = get_block; dio->end_io = end_io; dio->map_bh.b_private = NULL; + dio->map_bh.b_state = 0; dio->final_block_in_bio = -1; dio->next_block_for_io = -1;
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